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Landcruiser H42 4 Speed Trans. to Landcruiser 3 speed T-Case

Landcruiser H42 4 Speed Trans. to Landcruiser 3 speed T-Case

Posted by Cruiser Outfitters on Mar 2nd 2022

This information covers the mating of the Toyota Landcruiser H42 4 speed transmission (came factory in 10/73' - 7/80' Landcruiser's) to the transfer case originally mated to the Toyota J30 transmission (63' - 9/73').

Frequently Asked Questions (FAQ):

Q: Why are the transfer cases referred to as "3 speed" or 4 speed"?
A: The name reflects the transmission they were originally mated to. It does NOT reflect the number of actual speeds the transfer case has. All transfer cases discussed in this conversion actually have two speeds, high and low, but as noted, for identification purposes they will be referred to as either "3 speed" or 4 speed".

Q: What is the advantage to this swap?
A: The "3 speed" TC has a lower low range gear ratio, giving you an slightly lower crawl ratio. The "4 speed" case has a 1.999 low range ratio as opposed to a 2.313 low range in the "3 speed". Both cases have a 1:1 high range in their stock form.

Q: Will my driveline's need modification?
A: No, the critical TC dimensions are the same. However, the flange patterns will need to be addressed. You can either re-use your existing flanges & park brake drums, or source new/used ones from a reputable dealer.

Q: Can I use a 8/80' and later Landcruiser H42 4 speed transmission?
A: No, the later 8/80' transmissions have a 19 spline output shaft and a bolt pattern not compatible with the one piece transfer cases. They were originally mated to a "split-case" design.

Q: Can I just swap the gears out of the "3 speed" TC into my "4 speed" TC case?
A: Yes, however it requires some special shimming and installation not covered in this article. This is known to be advantageous as the "4 speed" case is regarded to be a stronger aluminum case versus the more "brittle" case of the "3 speed".

Q: What if the extra low range of the "3 speed" TC isn't enough for me?
A: You should investigate the Advance Adapters Orion Transfer Case. It is available in both 3:1 and 4:1 versions, and requires very few modifications to your drivetrain. Read more here: http://www.cruiseroutfitters.com/advadapt.html

Q: What parts do I need?
A: Parts List:

1. "3 speed" Transfer Case - You can source this from many different years of Landcruiser's, but take note that some "3 speed" transfer cases came in a vacuum shift 4WD variety that will most likely need to be converted for your installation.

2. Transition Input Gear - The input gear of the "3 speed" TC has a 10 spline configuration while the output shaft of the "4 speed" TC is a 16 spline configuration. Likewise, the outside diameter tooth count on the 3 & 4 speed TC input gears are different, so it is crucial to obtain the correct input gear that has the needed 16 spline inside configuration and the 29 tooth outside configuration.
(Cruiser Outfitters Part# TCG60030 - $115.50 - OE Japanese)

3. Transition Input Bearing - The bearing on the back of the TC will need to be changed to a bearing having the same OD as the original and the ID of the 4 speed transmission's output shaft. This bearing is available at parts houses (Part# BCA RW114R or industry standard # 6306-32R-2NSL, the application is a 1974 - 1982 Datsun B210 pickup truck, rear axle bearing). It is also available here.
(Cruiser Outfitters Part# TCTG06306 - $52.50 - High Quality Japanese)

4. Transfer Case Input Seal & Gasket - At a minimum you will want to put a new seal in the front of the transfer case and replace the paper gaskets on the TC including the one between the transmission and the transfer case. Consider the possibility of doing a complete rebuild depending on the condition of the case.
(Seal - Cruiser Outfitters Part# TC42014 - $6.00)
(Gasket Set - Cruiser Outfitters Part# TCGK6980 - $18.50)
(Complete Rebuild Kit - Cruiser Outfitters Part# TC6975 - $190)

5. Transfer Case Linkage - The transfer case mechanism on the 3 & 4 speed cases vary in length and design. You will need to remove the shift fork actuator housing from your "4 speed" case and install it on the "3 speed" case. Likewise your existing "4 speed" linkage should be reused. If you don't have the parts, source used ones from a reputable shop.

6. PTO Spacer or PTO Gear - The PTO gear or spacer that is currently inside of the "3 speed" case will not fit over the 4 speed transmissions output shaft. Thus, you must use your old PTO spacer or PTO gear from your current "4 speed" transfer case. If you don't have the parts, source used ones from a reputable shop.

7. Transfer Case to Transmission Bolts - Your existing 4 speed bolts should work just fine, if you don't have the parts, source used ones from a reputable shop.

Q: What else do I need to consider?
A: There are numerous variables not discussed in this article as every swap is a case by case situation. However, there are a couple items to discuss that will help make the conversion go smoother.

  • The Hi - Low lever on the top of the "3 speed" TC will need to be rotated to match that of the "4 speed" TC. This needs to be done before the transfer case is installed in the vehicle for best access.
  • If you can't easily remove the 2WD - 4WD actuator housing, it is also possible to remove the entire front output assembly from the "4 speed" case and install it on the "3 speed case". This option will also solve your front driveline pattern issue as you will no longer need to swap the front output flange.
  • It is possible to modify "3 speed" transfer case linkages to work with the "3 speed" 2wd-4wd shift actuator, however the amount of time to retrofit and modify they system and the fact you would then need to swap front output flanges make this route less appealing.

*See something missing, wrong, or incomplete? Please let us know!