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Step-by-Step Taller 5th Gear Swap (Dyna R452 into Tacoma R150F)

Step-by-Step Taller 5th Gear Swap (Dyna R452 into Tacoma R150F)

Filed under Engine and Driveline. See all how-to guides.

Sometimes, in an effort to make a Tacoma work really well off-road, modifications to the drivetrain result in the on-road performance being a little less than ideal. That's what happened to me - inadvertently - when I installed 4.88 gears in my front and rear diffs.

I've loved those gears - they are one of my best mods on the trail and at slower speeds - but the side effect has been that my RPMs are significantly higher than stock when I'm cruising on the freeway. In fact, I've ended up finding that 62mph - at about 2700 rpm - is about where the 5VZFE of the Tacoma likes to cruise, and that is... slow. It takes a long time to get just about anywhere.

I am not the first one to run into this problem, and in 2015, a thread over on Pirate4x4 was the first to provide a reasonably complete write-up of the steps necessary to swap the existing 5th gear in the R150F transmission of a 1st gen Tacoma for the 5th gear out of a Toyota Dyna R452 transmission.

The point of the Dyna 5th gear is to get a 30% overdrive as opposed to the standard [5th gear], but more on that later.

There is plenty of info on this scattered over the web but I couldn't find a single source that had all the info for someone that was coming from a basic understanding of gearboxes and wanted to try this themselves.

ToyotaLux

Unfortunately, even in that thread, it wasn't totally clear what parts were needed, and the photos - uploaded to the once great photo sharing site - have been defaced with a photobucket watermark, making them tough to interpret. So, I'm going to try to capture much of the same information here, as well as some updates, hopefully allowing others to complete this process with confidence.

A big thanks to everyone who participated in this investigation/conversation/swap prior to me, and to Dan @drr and Alex @Bandido with help sourcing parts, and to Zane @Speedytech7 for help with the swap itself!

Before We Get Started: A Word of Warning from ToyotaLux and boagreg

A few people have mentioned to me that they could not get the 5th gear off the output shaft as it is pressed on.

  • It seems that if you have the older R15x series with the nut on the end of the counter shaft then this mod becomes more difficult.
  • On my R150F series (circlip on the counter shaft) the 5th simply slid off and on by hand.

I went back to the R151 series manual and found that the 5th gear is indeed pressed on for these older model R series transmissions.

Further, two people who have managed to get the 5th gear off these older R series boxes with the nut have found the parts listed below do not fit their gearboxes.

So before buying anything check what box type you have as there seem to be differences in the R150x series transmissions, depending on age.

In order to do this modification using the parts listed below, you must use a 96+ R150F transmission with a circlip securing 5th counter gear on the counter shaft.

The yellow circled areas show the difference between the R151, PRE 95 R150 and the 96+ R150. While the internals are the same across all three, the newer 96+ R150 was changed slightly in the rear tail-housing:

  1. The reverse shift fork is different.
  2. The output bearing is smaller.
  3. A snap ring is used instead of a nut for the counter shaft.

Different gear boxes by age.

What Are We Even Doing?

A transmission adjusts the gear ratio between the engine and drive wheels, favoring more torque (ratios >1.0) at low speeds, and speed over torque (ratios <1.0) as momentum increases.

Transmission 1st 2nd 3rd 4th 5th
(overdrive)
R151* 4.313 2.330 1.436 1.000 0.836
R150F 3.830 2.062 1.436 1.000 0.836
R452 23 / 49 (5th and counter gear tooth counts) = 0.469
0.469 * 1.482 (cluster ratio) = 0.695		 0.695

Thus, by installing the R452 5th gear into the R150F, the overdrive will increase from 16.4% to 30.5%, or approximately 500 rpm at 65 mph.

* Shown for completeness, since some R150F transmission owners like to swap to R151 transmissions, in order to get lower gearing in 1st and 2nd gear. Note that the swap outlined here is not compatible with R151 transmissions.

Parts

Sourcing parts for this job is difficult for several reasons:

  1. They are not parts associated with the R150F transmission, so VIN lookups will suggest that they do not fit.
  2. They are parts associated with a transmission that was largely used overseas.
  3. The transmissions they were associated with had multiple variations, and the parts necessary for this swap were only used in certain years/configurations of the transmission.
  4. Over the years, new part numbers have superseded original numbers.

Most of what you'll need.

As such, trying to source parts from a used/junkyard R452 is not recommended. Further, I've listed several possibilities for purchasing the parts, as they can be difficult to find. Multiple orders may be necessary.

Note: As of October 2024, all parts can be ordered through MegaZip.

Part Part Number MegaZip
(recommended)		 Amazon Partsouq Amayama
Output Shaft Parts
Gear, 5th 33336-25030 (link) (link) (link)
Bearing Radial Ball, Roller (for Output Shaft Rear) 90363-30075 (link) (link) (link)
Countershaft Parts
Washer, 5th Gear Thrust 33346-71010 (link) (link) (link)
Gear, Countershaft 5th 33046-25030 (link) (link) (link) (link)
Bearing (for Counter 5th Gear) 90364-30009 (link) (link) (link)
Key, Synchromesh Shifting, No. 3 (3) of
33394-35040		 (link) (link) (link)
Spring, Synchromesh Shifting Key (for No. 3 Clutch Hub) (2) of
33392-14020		 (link) (link) (link)
Ring, Synchronizer, No. 3 33369-35011 (link) (link) (link)
Sleeve, Transmission Hub, No. 3 33395-35041 (link) (link) (link)
Piece, Gear Spline, No. 5 33318-35050 (link) (link) (link)
Ring, Shaft Snap for Counter Gear 90520-22016 (link) (link) (link)

Tools

The following tools are recommended to do this job. In some cases you might be able to substitute another tool with similar functionality, but these are the tools that were used - or that I recommend - in this step-by-step guide.

Additionally, this job requires removal of the drive shafts and transfer case, so you'll also need the tools necessary for that job, which is covered in Step-by-Step Replacing the Transfer Case on a Tacoma.

Supplies

There are a few consumables needed for this job as well.

Doing the Job

Most of the work in doing this job is removal of the transfer case. However, as it is much nicer to work on the transmission when there is a little more room under the truck, the first order of business is to get the truck a little higher off the ground.

  1. Place two (2) 6-inch vehicle ramps in front of the front tires.
  2. Drive the truck onto the vehicle ramps.
  3. Using a floor jack under the rear diff, raise the rear end of the truck until it is level with the front.
  4. Place two (2) jack stands under the rear axle near the leaf springs to support the rear end of the truck.

Even 6 inches of additional space under the truck makes it a much nicer place to work.

Removing the Drive Shafts and Transfer Case

To remove the drive shafts and transfer case, follow the instructions in the first half of Step-by-Step Replacing the Transfer Case on a Tacoma.

Note: There is no need to drain the oil out of the transfer case prior to removal, so start at the section entitled "Disconnecting and Removing the Front Drive Shaft." After completing the section entitled "Removing the Transfer Case," continue with the steps in this guide.

Removing the Transmission Shifter

With the transfer case already removed, removal of the transmission shifter is a simple process, necessary in order to remove the transfer adapter in a future section.

  1. Using a small pick tool, pry the rubber boot that connects the transmission shift levers to the base away from the base.

    Remove boot in order to access retaining ring.

  2. Using two fingers, press down on the retaining ring of the transmission shifter, and rotate it counter-clockwise until it releases and is pushed up by the internal spring. Remove the shifter from its socket.

    Unseating the retaining ring.

  3. Remove the transmission shifter and set it aside. Plug the hole with a shop rag in order to keep debris out of the transfer adapter.

Removing the Transmission Crossmember

  1. Position a transmission jack under the transmission, forward of the cast iron bearing plate which sits forward of the transfer adapter that will be removed.
  2. Raise the jack until it contacts the transmission but does not apply significant upward force.

    Preparing to support the transmission once the crossmember is removed.

    Note position of support, in front of the bearing plate.

  3. Remove the two (2) 12mm bolts that secure the exhaust bracket to the transmission crossmember. Label and set aside. Wedge the exhaust bracket above the exhaust and out of the way.

    Removing the exhaust bracket.

  4. Remove the four (4) 12mm bolts that secure the transmission mount to the transmission cross member, through the bottom of the crossmember. Label and set aside.
    • Note: this means that the transmission mount remains attached to the transmission, which is fine.
  5. Using a 14mm socket, and a 14mm wrench to hold the corresponding nuts, remove the four (4) 14mm bolts that secure the crossmember to the frame.

    Be sure the transmission is supported before removing the crossmember.

  6. Remove the crossmember and set aside.

Removing the Transfer Adapter from the Transmission

On an R150F transmission, all of the 5th gear components sit behind the cast bearing plate and are contained in the transfer adapter. This transfer adapter is secured by ten (10) 14mm bolts and form-in-place-gasket (FIPG).

  1. Using a 14mm socket and the necessary extensions and wobble adapters, loosen and remove the ten (10) 14mm bolts that secure the transfer adapter to the transmission. Label and set aside.
    • Note: when removing these bolts, be sure to note any wiring harness clips that were captured, so that they can be recaptured on installation.

    Transfer adapter fasteners.

  2. Using a gasket scraper / wedge / thin chisel and mallet, carefully break and separate the FIPG that secures the transfer adapter to the cast bearing plate.
    • Note: It is critical that you not disturb / break / separate the FIPG that seals the cast bearing plate to the transmission. This bearing plate is secured to the transmission with the same bolts that secured the transfer adapter, so care is necessary in order to ensure it is not disturbed.

    Splitting the FIPG.

  3. With the FIPG seal broken, the transfer adapter cannot be pulled straight off the back of the transmission. Rather, it must be rotated slightly counterclockwise in order to disengage the shift lever from the shift forks.

    Shift fork disengagement.

  4. Set the transfer adapter aside.

Confirming Your Transmission

With the transfer adapter removed, it is important to verify that the 5th gear swap will work prior to removing the stock components from the transmission.

To verify, check that the output shaft bearing is secured by a circlip and that the 5th counter gear assembly is secured to the counter shaft by a circlip. If either or both of the shafts have a nut on the end, the swap will not be possible. For more details, see A Word of Warning from ToyotaLux and boagreg.

Verify circlips on both shafts.

Removing the Stock 5th Gear, 5th Counter Gear, and Shift Fork

After validation that a compatible R150F transmission is in hand, removal of the stock 5th gear can proceed.

  1. Using a flat head screwdriver, tap the circlip on the counter shaft until it beings to release from the counter shaft. Remove and set aside.
    • Note: this circlip will not be reused, so if it is ruined in removal, that is OK.

    Removing circlip from counter shaft.

  2. Using a flat head screwdriver, tap the circlip on the output shaft until it beings to release from the output shaft. Remove and set aside.
    • Note 1: this circlip will be reused, so be careful when removing it.
    • Note 2: It may be necessary to prevent the output shaft from rotating by using a strap wrench to clamp the output shaft.

    Removing circlip from output shaft.

  3. Place a 2- or 3-jaw puller over the bearing on the output shaft. If possible, capture the inner race of the bearing with the jaws in addition to the outer race.
    • Note 1: Pulling the bearing off in this way is not good for the bearing. Replace it with a new one, even if it looks OK after removal.
    • Note 2: A bearing puller can be used here as well, but proximity to the counter 5th gears often means that a bearing puller cannot be maneuvered into position in order to grab the bearing.
  4. Tighten the 2- or 3-jaw puller slowly until the bearing is removed from the output shaft.

    Pulling the bearing from the output shaft.

  5. Remove the spacer collar by sliding it off of the output shaft.

    This spacer/collar should slide right off the output shaft.

  6. Align a 5mm punch with the roll pin on the passenger side of the shift fork.
  7. Use a hammer to carefully tap the roll pin toward the driver side of the transmission to extract it from the shift fork.
    • Note: This roll pin will be reused.

    Roll pin removal.

  8. Verify that the shift fork is no longer bound to the shift rail.
  9. Thread two (2) 50mm long, M8 x 1.25 bolts through a Harmonic Balancer Puller and into the 5th spline gear on the countershaft.

    Pulling the spline gear.

  10. Slowly tighten the Harmonic Balancer Puller in order to pull the 5th spline gear off the countershaft.
    • Note: While pulling the spline gear, be careful that the shift keys and springs inside the golden synchro ring remain in place. Or, that you at least keep track of them.

    With the spline gear removed, the synchro ring and shift keys are exposed.

  11. Carefully grasp the remainder of the 5th gear counter and shift fork assembly and slowly remove it as a single unit.
  12. Remove the thrust washer behind the 5th gear counter and shift fork assembly by sliding it off the countershaft, being careful not to lose the small key that indexes it on the countershaft.
  13. Remove the 5th gear by sliding it off the output shaft.

Components of stock 5th gear that have been removed.

Partially Assembling the Dyna R452 5th Counter Gear

Before the new Dyna R452 5th gear can be installed, it needs to be partially assembled - by positioning the shift keys and springs - on the bench.

  1. Place the 5th counter gear (33046-25030) on the bench with larger side of the gear down and the smaller side of the gear facing up.
  2. Place the Sleeve (33395-35041) over the 5th counter gear, being sure to align the shift key locations between the two components.
    • Note: the faceted side of the sleeve faces up, and toward the rear of the vehicle.

    Installing the sleeve.

  3. Insert the three (3) shift keys (33394-35040) into the slots between the 5th counter gear and sleeve.
    • Note: the shift key must be oriented so that the side with a single large "pad" faces out.

    Shift key orientation.

    Shift keys inserted.

  4. Insert two (2) shift key springs (33392-14020) into the 5th counter gear - overlapping the shift keys as shown - so that each shift key is captured by two springs.

    Shift key springs installed.

  5. Align the golden synchro ring (33369-35011) and spline gear (33318-35050) with the shift keys and place them over the 5th counter gear.

    Completing the assembly.

With assembly complete, it is important to exercise the 5th counter gear assembly in order to properly seat, capture, and align the shift keys and springs.

  1. Being careful to not move it too far, slide the sleeve up and down on the assembly until it seats without capturing the spline gear at all, and so that it captures the spline gear completely. As you do this, you will hear and feel the sleeve, shift keys, and springs "click into place" at various points.
    • Note: moving the sleeve too far up or down may cause the shift keys and springs to escape. If this happens, restart the assembly process.
  2. Slide the sleeve all the way down onto the 5th counter gear assembly and remove the spline gear and golden synchro ring.
  3. Inspect the position of the shift keys and springs. The lip of each shift key should be registered on the top side of the uppermost spring.

Verifying proper registration of the shift keys.

Installing the Dyna R452 5th Gear, 5th Counter Gear, and Shift Fork

With shift key and Dyna R452 5th gear operation verified, it is time to install the new gear set onto the output and countershafts.

  1. If they are in place, remove the spline gear and golden synchro ring from the 5th counter gear assembly.
  2. Place the spline gear and Output Shaft Ball Bearing (90363-30075) into a 200°F oven to expand them slightly. This will make it easier to press them onto their respective shafts in the transmission.

    Pro Tip: Your next piece of toast will taste a bit... "shoppy."

  3. Slide the 5th gear (33336-25030) onto the output shaft with the wider shoulder toward the front of the transmission.
  4. Slide the 5th gear thrust washer (33346-71010) onto the countershaft, capturing the key that indexes it onto the countershaft.

    5th gear and thrust washer installed.

  5. Insert the two halves of the Needle Bearing for Counter 5th Gear (90364-30009) into the back side of the 5th counter gear assembly.

    Bearing installation.

  6. Slide the original R150F shift fork into the groove in the sleeve on the 5th counter gear assembly and position the sleeve so that the shift fork remains parallel to the surface of the workbench.
    • Note: This means the sleeve will sit just below the golden synchro ring.

    Shift fork positioning.

  7. Slide the entire 5th counter gear assembly and shift fork onto the countershaft and shift rail.

    5th counter gear assembly and shift fork in place.

  8. Insert the roll pin into the shift fork and gently tap it in with a hammer until it contacts the shift rail.
    • Note: Gently tapping the roll pin until it contacts the shift rail will make it easier to align the two in the next step.
  9. Carefully slide the shift fork on the shift rail in order to align the roll pin with the hole in the shift rail.
    • Note: Be careful during this operation to ensure that the shift keys and springs do not jump out of the 5th counter gear assembly.
  10. Gently tap the roll pin into the shift rail with a hammer until it is flush with the surface of the shift fork.

    Inserting the roll pin.

  11. Place the golden synchro ring onto the 5th counter gear assembly and hold it in place with a bit of tape or someone else's finger.

    This synchro ring must be held in place as the spline gear is pressed onto the countershaft.

  12. Wearing a heat-resistant glove, align the spline gear with the teeth onto the countershaft.
  13. Using a 27mm socket (or the appropriate size sleeve) and hammer, tap the spline gear onto the countershaft until it is completely seated.
    • Note 1: You will know it is completely seated when the groove for the circlip is exposed and the rear-facing surface of spline gear is flush with the front-facing edge of the groove.
    • Note 2: unlike the original spline gear, the R452 spline gear does not have threaded holes to assist in removal, so be careful to not over drive it, as it is more difficult to remove.
  14. Align the new Shaft Snap Ring for Counter Gear Circlip (90520-22016) with the groove on the countershaft.
  15. Use a pair of channel lock pliers to press the circlip into place.
    • Note: Ensure this circlip is fully seated in the groove.
  16. Place the original spacer collar onto the output shaft.
  17. Wearing a heat-resistant glove, slide the output shaft ball bearing over the teeth on the output shaft until it contacts the smooth part of the shaft.
  18. Using a 32mm socket (or the appropriate size sleeve) and hammer, tap the output shaft ball bearing onto the output shaft until it is completely seated.
    • Note: You will know it is completely seated when the bearing contacts the sleeve, the groove for the circlip is exposed, and the rear-facing surface of bearing race is flush with the front-facing edge of the groove.

    Installation of "pressed" parts.

  19. Align the original output shaft circlip with the groove on the output shaft.
  20. Use a pair of channel lock pliers to press the circlip into place.
    • Note: Ensure this circlip is fully seated in the groove.

Yay!

Dry Fitting the Transfer Adapter to Test Operation of the Dyna R452 5th Gear Set

While the steps in this section are not mandatory, they do help to ensure that the 5th Gear Set that was just installed functions correctly by ensuring that the transmission shifter can engage the new 5th gear.

As with removal, the transfer adapter must be rotated into position on the back of the transmission in order for the shift lever to reengage the shift forks. Dry fitting the transfer adapter will allow you to practice this operation prior to performing it for the final time when FIPG is in place, allowing you to get a feel for how to maneuver the transfer adapter.

  1. Hold the transfer adapter approximately in place, but rotated slightly counter-clockwise from the final orientation.
  2. Push the transfer adapter slightly forward into position while rotating slightly clockwise to engage the shift lever with the shift forks.
    • Note: this is a finicky operation, don't force it. Do it a few times to get the feel of it.
  3. Install two (2) 14mm bolts, one on either side of the transfer adapter until they are just tight, but not torqued, in order to hold the transfer adapter in place.
  4. In the cab, insert the transmission shift lever into the transmission socket, ensuring that it seats correctly into the transmission.
  5. Using two fingers, press down on the retaining ring of the transmission shifter, and rotate it clockwise until catches on the two pins on the inside of the socket, holding the shifter in place.

If the R452 5th gear set was correctly installed, and the shift lever correctly engaged the shift forks when the transfer adapter was installed, then you should now be able to shift through all of the gears.

  1. Work the transmission shift lever into each gear, including the new 5th gear, in order to ensure that each gear works correctly.
    • Note: It may be difficult to shift through gears in order (1 - 2 - 3 - 4 - 5). If so, try 1 -  3 - 4 - 2 - 5.

    If you could see inside the transfer adapter, you would see the shift fork in these positions when 5th gear was disengaged (left) or engaged (right).

If you were unable to shift through all of the gears, remove the transfer adapter and ensure that you can engage 5th gear by manually moving the shift fork and spline gear.

  • If you can engage 5th gear by manually, then the transfer adapter was not installed correctly.
  • If you cannot engage 5th gear by manually, then the 5th gear set was not installed correctly.

Once the transmission is able to shift through all of the gears, continue:

  1. Using two fingers, press down on the retaining ring of the transmission shifter, and rotate it counterclockwise until it releases and is pushed up by the internal spring. Remove the shifter from its socket.
  2. Remove the transmission shifter and set it aside. Plug the hole with a shop rag in order to keep debris out of the transfer adapter.
  3. Remove the two (2) 14mm bolts that are temporarily supporting the transfer adapter.
  4. Remove the transfer adapter by rotating it slightly counterclockwise as it is pulled back, in order to disengage the shift lever from the shift forks.

Installing the Transfer Adapter to the Transmission

With the dry fit complete and functionality verified, it's time for final assembly.

  1. Carefully clean the old FIPG mating surfaces of the transmission and transfer adapter using brake cleaner and a single edge razor blade.
    • Note: be extremely careful to not mar the surfaces, while removing nearly all of the old FIPG so that you can create a good seal.
  2. Spread a small bead of FIPG onto the transfer adapter, being sure to completely encompass each bolt hole.

    A little FIPG goes a long way, but there can be no gaps in the bead.

  3. Hold the transfer adapter approximately in place, but rotated slightly counter-clockwise from the final orientation.
  4. Push the transfer adapter slightly forward into position while rotating slightly clockwise to engage the shift lever with the shift forks.
    • Note: this is a finicky operation, don't force it. Note2: If the FIPG contacts the transmission surface before the transfer adapter is properly oriented, verify that there is no break in coverage.
  5. Install two (2) 14mm bolts, one on either side of the transfer adapter until they are just tight but not torqued, in order to hold the transfer adapter in place.
  6. Install the remaining eight (8) 14mm bolts that secure the transfer adapter until they are just tight but not torqued.
    • Note: when installing these bolts, be sure to recapture any wiring harness clips that were previously captured.
  7. Allow the FIPG to set for 15 minutes prior to torquing.
  8. In a star pattern, torque the ten (10), 14mm bolts that secure the transfer adapter to the transmission to 27 ft-lbs.

Torquing to 27 ft-lbs in star pattern.

Be sure to allow at least 24 hours before filling the transmission with gear oil so that the FIPG can fully cure.

Installing the Transmission Shifter

  1. In the cab, insert the transmission shift lever into the transmission socket, ensuring that it seats correctly into the transmission.
  2. Using two fingers, press down on the retaining ring of the transmission shifter, and rotate it clockwise until catches on the two pins on the inside of the socket, holding the shifter in place.
  3. Reseat the rubber cover for the transmission shift lever.

Installing the Transmission Crossmember

  1. Move the transmission crossmember into place until the plastic alignment pin drops into the crossmember.
  2. Install the four (4) 14mm bolts and nuts to secure the crossmember to the frame.
    • Note: the bolts insert from the front, and nuts are on the rear. Tighten, but do not torque.
  3. Remove the transmission jack from under the transmission.
  4. Torque the four (4) crossmember bolts to 48 ft-lbs.
  5. Install and torque the four (4) 12mm bolts that secure the transmission mount to the crossmember. Torque spec: 13 ft-lbs.
  6. Install the two (2) 12mm bolts that secure the exhaust bracket to the transmission crossmember. Torque to 13 ft-lbs.

Installing the Transfer Case and Drive Shafts

To reinstall the transfer case and drive shafts, follow the instructions in Step-by-Step Replacing the Transfer Case on a Tacoma.

Finishing Up - oil into transmission, test drive

Before filling the transmission with gear oil, be sure to allow the FIPG to cure for 24 hours.

  1. Using a 24mm socket, remove the fill plug from the transmission.
  2. Fill the transmission with gear oil until oil begins to leak from the fill plug, approximately 3.7 quarts.
  3. Using a 24mm socket, install the fill plug on the transmission. Torque to 27 ft-lbs.
  4. Using a 24mm socket, check the drain plug on the transmission. Torque to 27 ft-lbs.
  5. Remove any jack stands or ramps from under the vehicle.

Take it for a test drive! Congratulations, you're done!

 

 

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