3-speed transmission swap to a 4-speed? (1 Viewer)

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NYIronPig

YES I have a problem...
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I am looking to improve my rig by upgrading my stock 3-speed tranny. I have looked at the 5-speed option, but it gets very expensive with all that is needed. Have read a lot that the 4-speed makes the FJ40 a nicer daily driver. Besides getting the H41 4-speed transmission and bell house, what else do I need? Can I use my current T-Case, or do I also need a new one? Just want to see what all is involved from parts and labor before I jump in. Thanks for any help advice you can offer me!
 
I know I have ran acrossed some detailed 3 to 4 swap info posted by LivingInThePast. Figured I'd mention that so you can read what he's posted while you wait for others to chime in.
 
You can use your current t-case and many consider it the preferred way due to the low range. More on that here:
Cruiser Outfitters
 
Now this looks like it could be a great solution for me. Now I just need to find a H42 4-speed transmission. I assume the H41 will not work as well?
 
Yes, you can use your current 3 speed t/c. However, you will need a different PTO gear or a spacer. Places like Marks Off Road or Cruiser Outfitters sells them. You will also need longer T/C to Tranny bolts (i.e. the 4 speed T/C bolts). If you have the vacuum transfer case, you will have to lengthen the the hi/low actuator rod by a couple of inches.

Other things to consider, you will either need 4 speed drive lines, or you will have to have your rear shortened and the front lengthened (no, you can't just swap them front to back - they won't fit). This set up also gets real close to the cross member behind the parking brake. I cut mine out, rotated it back, and made it removeable. It makes life much easier when dealing with the parking brake or removing the tranny. This is how I made mine removeable (ignore the booger welds- it was early on in my welding career):

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Good luck. And since I've been typing there have been a couple of responses. You can use an H41 or H42. The only difference is the H41 has a lower 1st gear.

*Edit* Something else to keep in mind, most writeups talk about bolting a 3 speed case to your existing 4 speed. The link from Cruiser Outfitters is like this as well. It is a little different when you are adapting your current 3 speed case to a swapped in 4 speed tranny. Just an fyi.

:cheers:
 
Now this looks like it could be a great solution for me. Now I just need to find a H42 4-speed transmission. I assume the H41 will not work as well?

So long as it's a 16 spline output it will, it too was available in 16 and 19. 19 will only mate to the Split Case.
 
If I find the 4-speed with the original T-Case attached, would this be an easier/better way to go rather that trying to mate it to my 3-speed t-case?
 
If I find the 4-speed with the original T-Case attached, would this be an easier/better way to go rather that trying to mate it to my 3-speed t-case?

Well, it's a tough call. Use your t-case and your drivelines bolt right up and up get the lower low-range. Use the 4spd TC and you theoretically don't have to split them or buy conversion parts. Did you see they link I shared above?
 
Thanks Cruiseroutfit! Link is EXTREMELY helpful!
 
If I find the 4-speed with the original T-Case attached, would this be an easier/better way to go rather that trying to mate it to my 3-speed t-case?

This is the best way to go, I just went through this and by the time you get everything you need to make it work it will cost you more in the long run. Just find someone who is selling a 4speed/t-case combo and slap it in. If you have any questions feel free to PM me
 
Thanks just found a 4-speed with the matching Tcase!
 
Thanks just found a 4-speed with the matching Tcase!
That's the easiest solution. I put an H42/4-speed transfer case from a '78 FJ55 into my '71 FJ40 more than 15 years ago and it works great.
 
Resurrecting an old thread.

I am replacing my 3 speed transmission in my 1970 FJ40 with a 4 speed (H42 with coarse spline). So a 4 speed transmission to a 3 speed TC. I have the 4 speed bell housing and tranny. A few questions for those few that have done this modification:

Can I reuse my:
A) starter (I am reusing 3 speed fly wheel and pressure plate - I read somewhere this works)
B) clutch slave cylinder (or do I need the 4 speed slave)
C) drive lines - I am thinking I need 4 speed since the 4 speed tranny is slightly longer

I am using the manual floor shift TC (not the vacuum). Does either the 3 or 4 speed shift lever to TC link work (ie fit without alteration)? Or do I have to cut the link to create the correct length?

Thanks for any help

@cruiseroutfit
@FF LC FREAK
@Living in the Past
 
The 4-speed throw-out fork needs a 4-speed slave push rod.

You will need 4-speed driveshafts, but they won't have the same pattern at the differential or transfer case. They can either be extended, or you can get the parts from a later transfer case.

There was an early 4-speed shift linkage, and a later 4-speed shift linkage. It must match the 2/4, and the high/low parts on the transfer case.

I take it that you sourced the 'transition era' gear in the transfer case, and the Datsun B10 axle bearing?
 
The 4-speed throw-out fork needs a 4-speed slave push rod.

You will need 4-speed driveshafts, but they won't have the same pattern at the differential or transfer case. They can either be extended, or you can get the parts from a later transfer case.

There was an early 4-speed shift linkage, and a later 4-speed shift linkage. It must match the 2/4, and the high/low parts on the transfer case.

I take it that you sourced the 'transition era' gear in the transfer case, and the Datsun B10 axle bearing?
Datsun B-210 RW-114 rear wheel bearing - ID is 32mm, OD is 72mm.
 
The 4-speed throw-out fork needs a 4-speed slave push rod.

You will need 4-speed driveshafts, but they won't have the same pattern at the differential or transfer case. They can either be extended, or you can get the parts from a later transfer case.

There was an early 4-speed shift linkage, and a later 4-speed shift linkage. It must match the 2/4, and the high/low parts on the transfer case.

I take it that you sourced the 'transition era' gear in the transfer case, and the Datsun B10 axle bearing?


Depends on which pressure plate your using what clutch fork/throw out bearing you use. Many years ago when I switched my 68 to a four speed switch to a four speed bellhousing and kept everything else from the three speed.

My 79 FJ40 has a shift linkage made from the earlier and later shift linkage. Actually works very well. Only thing I can think is some time in the past a PO changed out the case and didn't change the top cover on the transfer case. Not sure the month but is from 74 with a four speed.
 
Thanks guys - good info. It helped a lot. Found the transition gear and bearing. Need to find the drive shafts and shift linkage.


Keep in mind the flange pattern for driveshafts could be different. The four speed is right at three and half inches longer. When I did mine I had my driveshaft retubed to the correct length. That was before the internet with many options for parts and information. Today will go with four speed driveshafts when I finally getting around to my 73 FST.
 
Keep in mind the flange pattern for driveshafts could be different. The four speed is right at three and half inches longer. When I did mine I had my driveshaft retubed to the correct length. That was before the internet with many options for parts and information. Today will go with four speed driveshafts when I finally getting around to my 73 FST.

I can swap the 3 speed flange into the 4 speed driveshaft on each end, right?
 

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