Driveshaft Mystery ??? Driveshaft Flange Differences (1 Viewer)

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Bowling Green, KY
It's been a very long road for my 81 restomod. I've started and stopped several times, my wife had our 3rd child, my mom and dad in and out of the hospital....yeah, yeah, yeah. It's been 4 years since I brought the 40 home and now Ive stumbled on yet another set back.

Many moons ago I took the rear diff cover off to find a welded pinion pin. https://forum.ih8mud.com/40-55-series-tech/200626-welded-pinion-nut.html

I ended up buying a 3.71 FJ60 rear third from a fellow mudder. I believe it was an 84 and swapped them into the housing to set there for the next 3 years. I was told the driveshaft flange should be identical to my 1981 FJ40 but if not I could drill holes in the FJ60's round driveshaft flange (plenty of room).

I also recall having a time removing the rear driveshaft and thinking it was too short. Had to loosen the u-bolts to remove the driveshaft.

So the last 2 weekends I put all new rear brake shoes, wheel cylinders, rear bearings, rubber seals, etc.

I thought I would break out the rear driveshaft to see how it fits. I got it to fit, but the flange is completely different. In fact I measured the bolt holes and it matches the flange for a 8/69 to 1/74 (thanks to Cruiseroutfitters.com). Bolt holes are 10 mm on the diff side and 11 mm on the Transfer Case side. :bang:

BTW which end of the driveshaft connects to the TC and which end connects to rear diff? Seen it both ways.

Now Im wondering if my front third is 3.71 or 4.11??? How can I tell without tearing it apart?

Is it possible to frankenstein an early model driveshaft and a late model driveshaft?

Experts please chime in.
Driveshaft Flanges.JPG
My Driveshaft flange to driveshaft.JPG
 
Sounds just like me, even the family delays :lol:

I ordered a 5.29 gearset and the pinion flange looked just like yours. It was for Toyota but turns out it was mini truck stuff and the bolt patterns are slightly different between the LC and mini trucks :eek:

I could get one bolt to line up and none of the others. I figured I would put the 76's pinion flange back in so they would match, nope I now have a fine spline pinion and the original flange is course spline :mad:

I ended up fixing it by welding the 3 holes shut that didn't line up (a couple of them were "close") and drilled them back out to match.

Good luck :)
 
Hey Alex, if your driveshaft seems too short, it's probably from an earlier model (parking brake drum makes it shorter). I also always thought the FJ60 flanges were the same as our late 40's, so that would also explain the mis-matched flanges.

Oh, and the driveshafts should be installed with the yolk end facing the TC.
 
Jeff...it's actually a little too long. There was no play in the shaft between the yoke and the shaft, it was bottomed out.

Aren't the splines different in the early driveshafts vs late driveshaft?

Or could someone have just connected the earlier flange at the U joint to the shaft itself?

I thought I could just drill new holes in the FJ60 flange and then drill out the driveshaft flange to accept 11 mm bolts. But like I said the fact that the drive shaft is stuffed between the TC and Rear Diff with no play can't be good, NO?
 
Did you remove the grease fitting from the slip and stub section of the drive shaft to try and compress it the rest of the way?
 
I have the same problem. My rear driveshaft will not fit the TC side due to the bolt pattern being different. I replaced the original four speed with a three speed. Do I have to replace the driveshaft.?
 
Yes I removed the grease zerk and like I said there is no more travel in the drive shaft. It is bottomed out.

It was also dry as a bone from neglect. I had to separate the halves with two ratchet straps in a homemade frame. BTW I didn't make any marks on both ends before I separated, oops.

What is the stock length of a late model rear driveshaft?

Oh yeah. The rear end is currently up on jack stands under the leafs. Should I support frame etc by the frame and see if the axle drops a little?
 
Ive decided to use the driveshaft and:

1) drill new holes in the pinion flange using the driveshaft flange as a template

or

2) order a Multi-year flange for the rear pinion to mate up to my existing driveshaft flange

But now I notice a very small drip of gear oil coming from the TC rear output shaft.

Is it possible to change this seal without getting into a TC rebuild?

Should I go ahead and change the seal with TC still attached to tranny. Is this easy?

I'm very new to all this so any critique is welcome.

Should I also replace front output shaft seal? What about seal on front diff???

Lots of questions for all you ...
 
Drip from the output shaft is usually caused by a small groove that's developed around your parking brake drum. You can replace the seal without removing the TC. Pull the parking brake and drum and pull the speedometer housing. The housing contains the seal. If you have a significant groove you can repair witha speedi-sleeve. Another options is to machine the speedo housing to accept a second seal.

Seal on the front of the diff is relatively easy. If you have time & $10-15, I'd replace it while you're there. If it fails later, it's easy to pull the drive line and do it then.

https://forum.ih8mud.com/40-55-series-tech/179274-transfer-case-speedo-double-seal-writeup-how.html

https://forum.ih8mud.com/40-55-series-tech/170034-feedback-mudraks-dual-seal-speedo-housing.html

https://forum.ih8mud.com/40-55-series-tech/163572-parking-brake-speedi-sleeve-drive-shaft.html

https://forum.ih8mud.com/40-55-series-tech/124825-do-i-need-speedi-sleeve.html
 
Thanks for the links. Ive got some reading to do.

My '81 has parking brake on the rear axle. I would guess the seal replacement and Speedi Sleeve fix still applies. I'll check it out.
 
Thanks for the links. Ive got some reading to do.

My '81 has parking brake on the rear axle. I would guess the seal replacement and Speedi Sleeve fix still applies. I'll check it out.

Speedi sleeve fix doesn't apply to our '81s. All you would have to do is replace the flanges. I have a couple Fj60 flanges if you need them. The seals can be easily replaced with the flanges removed.

Also, it would be best to keep the transfer case attached to the tranny to replace the output seals. The split transfer case doesn't just unbolt from the tranny like earlier models. You have to split it apart (completely disassemble it) to remove it. At that point it would be insane not to rebuild it.
 
Jeff.

The flange on my driveshaft is the early bolt pattern.

The rear diff flange is the round FJ60 variety with larger bolt pattern.

Do you have an extra rear drive shaft ??? or just the flange?

Does the rear output seal look like this? easy fix ???

(pics borrowed from Hugh Heifer)

Alex
TC Rear Output Seal.jpg
TC Rear Output Seal 2.jpg
 
Update. I bought a Multi-pattern pinion flange fro Kurt at cruiser outfitters and new oil seals for output flange and pinion.

Nobody really answered the question of mix matching a late yoke with early rear driveshaft but it seems obvious that this is what happened with mine.

I think kurts flange will solve that problem.
image-3783459844.jpg
 

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