Transmission & Drive Shaft Question

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FloridaLife

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If I swap out from a '71 F model engine & 3 speed transmission, to a '79 F2 engine with a 4 speed transmission connected to a 3 speed transfer case, will my original driveshaft work, or will I need to get a shorter one? I don't know if the length of the 3 speed and 4 speed are the same and/or close enough to us my driveshaft.

Thank you.
 
Longer front shaft. Shorter back shaft.

(Just get the OEM shafts from the rig you get the powerplant from). ;)

Mark...
 
No the shaft lengths change. Shorter in the back longer in the front. Also need to consider flange patterns.
Longer front shaft. Shorter back shaft.

(Just get the OEM shafts from the rig you get the powerplant from). ;)

Mark...

The flange pattern on the axle diffs will be different. Same with the transfer case if the original one from the three speed is used.
 
No the shaft lengths change. Shorter in the back longer in the front. Also need to consider flange patterns.

The flange pattern on the axle diffs will be different. Same with the transfer case if the original one from the three speed is used.
Yes, Different patterns. Easily addressed. I wasn't trying to solve all his problems with one-stop. Can't take all the joy of exploring away from him. 😉

Mark...
 
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I have to disagree with you on this one. If he uses his original transfer case then it is just a matter of modifying the length of the original shafts to fit the new configuration.
Quicker cheaper easier to swap shafts. Having his existing shafts shortened/lengthened will work too.

Mark...
 
Quicker cheaper easier to swap shafts. Having his existing shafts shortened/lengthened will work too.

Mark...

If you will review the diagram in post #1 of this thread you will see the flange difference.

If he went with the '79 shafts you have to play mismatch game. You'd have to change the flanges on the transfer case as well as both axles. More work and expense.
 
Alternatively, Tom Woods will custom make you a nice pair of drive shafts to your specification and ship them to you in a few days.
Yep, we are a dealer and have pretty much all lengths and patterns documented for pretty much all combos. Unless you are getting the OEM shafts for free it almost isn't worth the cost of shipping them these days, especially considering the OEM shafts will usually have worn slip yokes, worn u-joints.
 
Good to know, thanks. Any idea what that costs? And I've never heard of Tom Woods. Is he someone here in the forums?
If I recall right, a pair runs around $800.

IMG_0717.jpeg


IMG_0716.jpeg
 
If I recall right, a pair runs around $800.

View attachment 3634304

View attachment 3634305
Hmmm. Good to know! Thank you so much. I think I asked this before, but where on the Texas coast are you? I'm sad to say it, but I still have a place in East Texas that I have not seen in 20 years. August 1st, 2004, the day I buried my grandfather. My heart was broken, and I drove away and have never been back. 32 year military, my best friend, and my hero. He was everything to me. So when I left the cemetery and his 21 gun salute, I drove away and have never been back. The thought of fishing there without him was more than I could bare. Passed from my great great grandfather, 100 acres with a 46 acre lake, spring fed, with a cabin that sleeps 6. Now that I have 2 sons, part of me wants to take them and my wife to see where I came from, and where he is laid to rest, and part of me just can't bare it.

Also... on the monument in front of the Alamo, the names of 3 of my direct descendants are listed and died there in the Alamo, with their close friend who tham came from Tennessee with, Davey Crocket.

Have a good evening,
Don
 
Unfortunately, getting the drive shafts from the seller's rig is probably not an option since he originally had a 3 speed too, found / bought / had a 4 speed rebuilt and mated to a 3 speed transfer case to convert his rig to a 4 speed, but life and things come up and he never got it installed and is moving on to a completely different project. All that to say, the seller has 3 speed drive shafts.

Anyone know the differences between the length of the 3 speed transmission and the length of the 4 speed transmission?
 
Unfortunately, getting the drive shafts from the seller's rig is probably not an option since he originally had a 3 speed too, found / bought / had a 4 speed rebuilt and mated to a 3 speed transfer case to convert his rig to a 4 speed, but life and things come up and he never got it installed and is moving on to a completely different project. All that to say, the seller has 3 speed drive shafts.

Anyone know the differences between the length of the 3 speed transmission and the length of the 4 speed transmission?
I was once advised not to put the cart in front of the horse… Install the 4-speed/T-case then measure.
 
Yep, we are a dealer and have pretty much all lengths and patterns documented for pretty much all combos. Unless you are getting the OEM shafts for free it almost isn't worth the cost of shipping them these days, especially considering the OEM shafts will usually have worn slip yokes, worn u-joints.
Hey Matt, what is the difference in length of a 3 speed transmission and a 4 speed transmission? Also, what years of the FJ40 had the 4 speed?
I was once advised not to put the cart in front of the horse… Install the 4-speed/T-case then measure.
Indeed! Thankfully, I'm not too far away from cruisermatt's business. I just need to shop around to get top dollar on selling a kidney, then take my FJ40 to him and get it done right! ;)
 
I think I actually have the driveshafts you need. I converted to a 4 speed with the 3 speed transfer case about 10 years ago. Pulled it all out a couple months ago to replace the entire drivetrain. I can measure them for you.

I’ll probably go with new shafts from Tom Woods. The rear will need to be about 16” and the front about 36” or so. It is very easy and relatively cheap to get them re-sized. Just get your measurements and take them to a shop that builds driveshafts. I think it cost me $200?
Short one is the rear DS.
IMG_4960.jpeg

Edit: mine is a ‘67. You will need the kit to mate the 4 speed to the 3spd TC. Coarse to fine spline. 🤔or viseversa.
 
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I think I actually have the driveshafts you need. I converted to a 4 speed with the 3 speed transfer case about 10 years ago. Pulled it all out a couple months ago to replace the entire drivetrain. I can measure them for you.

I’ll probably go with new shafts from Tom Woods. The rear will need to be about 16” and the front about 36” or so. It is very easy and relatively cheap to get them re-sized. Just get your measurements and take them to a shop that builds driveshafts. I think it cost me $200?
Short one is the rear DS.
View attachment 3634942
Edit: mine is a ‘67. You will need the kit to mate the 4 speed to the 3spd TC. Coarse to fine spline. 🤔or viseversa.
Oh! You are the PERFECT person for me to meet! How big of a pain in the butt was it to go from a 3 speed to a 4 speed?

Was yours a 3 on the tree, and switched to a 4 on the floor? Thoughts? Like it, or not worth the effort?

To be open & transparent, I haven't driven a 3 on the tree since I was 15, but I 'used to be' awesome with a stick shift! Hope I still can. 39 years since both hips sort of reconstructed at age 16 (no titanium sockets then, so bone grafts & steel rods) + 20+ surgeries including low back & neck... Stick shift 'may' not be as fun as it used to be. LOL.

If those driveshafts are from a 4 speed rig, what would you want for them?
 

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