Gearbox swap (1 Viewer)

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Hi there,
I just purchased a 1977 fj40 from Indonesia with a 3 speed box. I have access to a 4speed box.
anyone know it it’s a straight swap?
 
Which 4-speed?

You'll probably need, all the parts on the transmission output shaft of a 4-speed, an input shaft gear from a 4-speed up to March '75, different propeller shaft lengths (flange patterns must be correct), the shift shaft and matching parts from a 4-speed, transmission hump (maybe), bolts from the 4-speed transfer case to transmission, and a 4-speed bellhousing (flywheel and clutch with slave pushrod can remain, but they must match). On early USA 40s the frame crossmember behind the parking brake drum is tight, and often requires the engine to be unbolted at the front mounts with the water pump fan cleared from the radiator shroud so that the engine can be tilted forward (you should measure your clearance because it is a '77). Expect gear wear on the 4-speed output shaft, and gear, which could require the use of an oil bypass hose from the transmission to the transfer case so that it doesn't overflow.

The output shaft of a 3-speed in my shop is perfect. I have two 4-speed transmissions that show normal wear at these locations and will probably leak oil from one box to another, making the bypass hose kinda necessary. The 3-speed has no synchronizer on first gear, so it makes downshifting hard from 2nd gear. The ratios of the 4-speed H42 are not that much better, the H41 is a whole different story. I know that this doesn't answer your question, but it is some things that I have considered.

Welcome to Mud.
 
Last edited:
Toyota 3 and 4 speed?
the bellhousings are different
make sure the 4 speed is from a gas engine or H series diesel
 
Toyota 3 and 4 speed?
the bellhousings are different
make sure the 4 speed is from a gas engine or H series diesel


Should be sure the four speed has a sixteen spline output shaft. Nineteen will not adapt to to the one piece transfer case and require a split transfer which will bring up a hand brake issue.
 
Which 4-speed?

You'll probably need, all the parts on the transmission output shaft of a 4-speed, an input shaft gear from a 4-speed up to March '75, different propeller shaft lengths (flange patterns must be correct), the shift shaft and matching parts from a 4-speed, transmission hump (maybe), bolts from the 4-speed transfer case to transmission, and a 4-speed bellhousing (flywheel and clutch with slave pushrod can remain, but they must match). On early USA 40s the frame crossmember behind the parking brake drum is tight, and often requires the engine to be unbolted at the front mounts with the water pump fan cleared from the radiator shroud so that the engine can be tilted forward (you should measure your clearance because it is a '77). Expect gear wear on the 4-speed output shaft, and gear, which could require the use of an oil bypass hose from the transmission to the transfer case so that it doesn't overflow.

The output shaft of a 3-speed in my shop is perfect. I have two 4-speed transmissions that show normal wear at these locations and will probably leak oil from one box to another, making the bypass hose kinda necessary. The 3-speed has no synchronizer on first gear, so it makes downshifting hard from 2nd gear. The ratios of the 4-speed H42 are not that much better, the H41 is a whole different story. I know that this doesn't answer your question, but it is some things that I have considered.

Welcome to Mud.
Dizzy - your a champion. Thanks for taking the time to respond and it does sound like a bit of a mission. i’m finding a few other ....issues which have now jumped the queue like steering and suspension. It’s got PWR steering and it’s leaking like a drive 😬.
But thanks again. Really appreciated 👍
 

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