Minimum rear driveshaft length lifted CJ2A?

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Grantshire View Drop Down

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Topic: Minimum rear driveshaft length lifted CJ2A?
Posted: 20 June 2019 at 4:04pm

Picked up a modified 46 CJ2A (2A body on early CJ5 frame) to finish building as my daughter’s trail rig. Strong running 225 with stock T90/18 behind it but tub was placed back on the frame giving it a 22” rear driveshaft. I have a butchered up M38 with a fiberglass body that someone dropped a 4.3/TH350/18 with Warn OD in. The 2A has Dana 44 axles with 5.38 gears so I am considering replacing the T90/18 with the TH350/18/Warn OD. I know that’s a longer combination but I think I am starting with a longer than normal driveshaft length. I don’t know the condition of the auto setup so I plan to rebuild/go through all of it.

Another option is a 700R4/Dana 300 swap (I gave the adapter and spare 300’s). This setup is longer than the TH350 one but is that an issue since I am starting with 22”?

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Posted: 20 June 2019 at 4:26pm

The length of rear propeller shaft is limited by several factors.

The rear suspension travel upward and downward travel is considered because this effects the joint angles.

The maximum cardan cross joint angle is limited between the companion flange and the companion yoke.

The longer yoke allows for a slightly increased propeller shaft angle.

Here we see the early shorter companion flange yoke next to the improved longer yoke:

The slightly longer #116714 flange was used on all CJ's prior to November 1962.

The slightly shorter #912105 flange was used on all CJ's after November 1962.

The slightly longer #116714 flange was used with the shorter 4 tooth drive gear Jeep # A-1511 / SW # 477021.

The slightly shorter #912105 flange was used with all other speedometer drive gears.

Here in this pic you see both early and later CJ yokes mentioned above.

Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

oldtime

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Posted: 21 June 2019 at 1:20am

My latest build has the absolute shortest rear propeller shaft that one can put onto an 80" wheelbase jeep without limiting travel of the rear suspension.

In other words if my rear propeller shaft was any shorter then the companion yoke would begin to bind whenever the rear axle is at full droop.

Mind you this particular flatfender was built with stock standard rear suspension.

The Monroe shocks allow for full travel of the standard rear suspension.

Some shocks like the Rancho's will limit the standard travel a little.

The rear propeller shaft assembly is 12-3/4" long when compressed.

The rear engine support crossmember was moved aft exactly 5-1/2" in order to fit a T98-A transmission using the factory bellhousing adapter plate.

So without limiting the rear suspension you can move the transfer case aft 5-1/2" IF you use the longer rear companion yoke.

I could not stuff the T98 up any higher.

In other words the jeep lost zero belly clearance and the D18 remains at the standard ride height.

If your jeep has been lifted even as little as 1/2" then that will increase the propeller shaft angle.

The propeller shaft length must then be increased so it does not bind at full droop or the transfer case must be lowered.

This pic shows a standard length rear shaft next to my shortened shaft...

This pic shows rear propeller shaft at maximum possible angle before the Cardan cross begins to bind in the companion yoke.

Note rear tire in the air.. so the rear axle is at full standard droop.

Standrad droop is limited by both the spring arch and the shock travel

Edited by oldtime - 21 June 2019 at 1:32am

Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

Bridog

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Posted: 21 June 2019 at 2:22am

Running a CV joint at the transfer case end of the rear driveshaft would also be a good option. That would allow you to rotate the pinion angle up to where it points at the transfer case output yoke. In doing so it reduces angle of the rear driveshaft as well as take advantage of a CV joint’s ability to operate at a higher angle.

Sounds like a cool project. Do you have any pics of it that you could post?

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Grantshire Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 15 June 2019 Location: Hanover, VA Status: Offline Points: 5	Post Options Post Reply Quote Grantshire Report Post Thanks(0) Quote Reply Topic: Minimum rear driveshaft length lifted CJ2A? Posted: 20 June 2019 at 4:04pm
	Picked up a modified 46 CJ2A (2A body on early CJ5 frame) to finish building as my daughter’s trail rig. Strong running 225 with stock T90/18 behind it but tub was placed back on the frame giving it a 22” rear driveshaft. I have a butchered up M38 with a fiberglass body that someone dropped a 4.3/TH350/18 with Warn OD in. The 2A has Dana 44 axles with 5.38 gears so I am considering replacing the T90/18 with the TH350/18/Warn OD. I know that’s a longer combination but I think I am starting with a longer than normal driveshaft length. I don’t know the condition of the auto setup so I plan to rebuild/go through all of it. Another option is a 700R4/Dana 300 swap (I gave the adapter and spare 300’s). This setup is longer than the TH350 one but is that an issue since I am starting with 22”?

oldtime Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 12 Sep. 2009 Location: Missouri Status: Online Points: 4186	Post Options Post Reply Quote oldtime Report Post Thanks(0) Quote Reply Posted: 20 June 2019 at 4:26pm
	The length of rear propeller shaft is limited by several factors. The rear suspension travel upward and downward travel is considered because this effects the joint angles. The maximum cardan cross joint angle is limited between the companion flange and the companion yoke. The longer yoke allows for a slightly increased propeller shaft angle. Here we see the early shorter companion flange yoke next to the improved longer yoke: The slightly longer #116714 flange was used on all CJ's prior to November 1962. The slightly shorter #912105 flange was used on all CJ's after November 1962. The slightly longer #116714 flange was used with the shorter 4 tooth drive gear Jeep # A-1511 / SW # 477021. The slightly shorter #912105 flange was used with all other speedometer drive gears. Here in this pic you see both early and later CJ yokes mentioned above.
	Currently building my final F-134 powered 3B . T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts

oldtime Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 12 Sep. 2009 Location: Missouri Status: Online Points: 4186	Post Options Post Reply Quote oldtime Report Post Thanks(0) Quote Reply Posted: 21 June 2019 at 1:20am
	My latest build has the absolute shortest rear propeller shaft that one can put onto an 80" wheelbase jeep without limiting travel of the rear suspension. In other words if my rear propeller shaft was any shorter then the companion yoke would begin to bind whenever the rear axle is at full droop. Mind you this particular flatfender was built with stock standard rear suspension. The Monroe shocks allow for full travel of the standard rear suspension. Some shocks like the Rancho's will limit the standard travel a little. The rear propeller shaft assembly is 12-3/4" long when compressed. The rear engine support crossmember was moved aft exactly 5-1/2" in order to fit a T98-A transmission using the factory bellhousing adapter plate. So without limiting the rear suspension you can move the transfer case aft 5-1/2" IF you use the longer rear companion yoke. I could not stuff the T98 up any higher. In other words the jeep lost zero belly clearance and the D18 remains at the standard ride height. If your jeep has been lifted even as little as 1/2" then that will increase the propeller shaft angle. The propeller shaft length must then be increased so it does not bind at full droop or the transfer case must be lowered. This pic shows a standard length rear shaft next to my shortened shaft... This pic shows rear propeller shaft at maximum possible angle before the Cardan cross begins to bind in the companion yoke. Note rear tire in the air.. so the rear axle is at full standard droop. Standrad droop is limited by both the spring arch and the shock travel Edited by oldtime - 21 June 2019 at 1:32am
	Currently building my final F-134 powered 3B . T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts

Bridog Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 04 Oct. 2016 Location: Holt, MO Status: Offline Points: 419	Post Options Post Reply Quote Bridog Report Post Thanks(0) Quote Reply Posted: 21 June 2019 at 2:22am
	Running a CV joint at the transfer case end of the rear driveshaft would also be a good option. That would allow you to rotate the pinion angle up to where it points at the transfer case output yoke. In doing so it reduces angle of the rear driveshaft as well as take advantage of a CV joint’s ability to operate at a higher angle. Sounds like a cool project. Do you have any pics of it that you could post?