Cj 5 rear drive shaft question

[elkgroveguy]

So I have a 1979 CJ5 with a
AMC 258 i6 / 4.2l , T-18 ,Dana 20 , AMC20 (axle)
It has a 2 1/2” Rancho springs, con-ferr shackles (5 1/4” hole to hole)
7/8” Transfer Case drop
I have a drive line vibration ,
pinion is 11 1/2 degrees, Transfer Case is 5 1/2 degrees
Other than doing a cv drive shaft any advise?
I really didn’t want to spend $400 on a new drive shaft and yoke.
Thanks in advance!

 

[HackFabrication]

Other than doing a cv drive shaft any advise?
I really didn’t want to spend $400 on a new drive shaft and yoke.

Have you checked the operating angles of the rear drive shaft? The 7/8" Transfer Case drop would have been standard with the T-18 OEM. Are there axle shims in place under the rear springs? If not, that is an option (use steel - most lift kits come with aluminum). Another option, but more labor intensive, is to cut the existing perches off the axle, rotate the axle to the correct angle, and re-weld. Or weld new ones on at the correct angle.

FWIW: I'm running a Tom Woods CV rear drive shaft on my 2.5" BDS lift, 76 CJ5 .

 

[jp360cj]

Are there axle shims in place under the rear springs? If not, that is an option (use steel - most lift kits come with aluminum).

This is great advice. I have personally had aluminum shims crush on my '7 (PO installed lift kit).

OP, I assume the tcase angle is down and the pinion angle is up? What the angle of the driveshaft itself? with that, you can calculate the u joint operating angles. I would re measure the tcase and pinion angles again when you measure the driveshaft angle to eliminate any difference in how the jeep is sitting.

With the operating angles, we can help you decide which direction to go, but I suspect you will need a double cardan (cv) shaft.

 

[elkgroveguy]

Thanks for the replies,
Transfer Case is pointing down 5.5* and pinion pointing up 11.5*
There are no shims in the rear axle at this time.
I did not measure the Drive shaft operating angle yet.
The vibration started when I switched the rear suspension.
I had a stock leaf pack with long add a leaf and the rear shackles have 2 bolt holes. (I had it in the longer of the two locations on shackle 6 1/2" eye to eye.)
With the old set up with no shims I had no vibration, With the new springs and rear shackle in the shorter bolt hole location the vehicle sits about 1 1/2" higher in the rear and I guess that is just enough to cause the vibration!
I do not think shims would help under the axle at this point because it would just make the difference between the 2 u-joints operating angles even more different.
I was thinking about making a bigger Transfer Case drop 1 1/2" compared to the 7/8" that it has now!
The Transfer Case drop would lessen the operating angle of the D.S. and make the operating angle of the u-joints closer to each other!

 

[jp360cj]

Shims on the axle can make it tilt either way, depending on which direction they're installed. Assuming you are still SUA, installing shims with the fat side to the rear will tilt the pinion down. About a 6* shim would get the pinion and tcase output close to parallel. However, it will also make the u joint operating angles higher. That's why you need to measure your driveshaft angle first. You may already to be too high on the u joint angles (or close to it).

I wouldn't drop the tcase down any further. Not only does it drop.tilt the tcase, it also tilts the engine, which will put more strain on the engine mounts and put the valve cover closer to the firewall. Not to mention the lost ground clearance.

If you end up needing a double cardan shaft, shop around. There are of a good driveshaft builders out there and you should be able to find one cheaper than $400, even with a yoke.

 

[Lumpy Grits]

Have you had that driveshaft apart recently?
You may have the slip-spline u-joint our of 'phase' with the other u-joint.
BTDT--
LG

 

[elkgroveguy]

Drive shaft is in phase (one of the first things I thought of as well)
Due to the fact that Im not wanting to spend the money on a cv drive shaft I think I might go back to my other spring set up for now.
I will check the D.S. operating angle tonight. and post that info.

I wish this site was easier about posting pictures!

 

[jp360cj]

The easiest way I've found to post pics is to take them with my phone and upload them via the tapatalk forum app.

You can also upload them to a host site and link them with the IMG tag. I used to use photobucket and it worked well before they screwed it all up. I don't know what would be a good host site nowadays

 

[JR74CJ5]

There is a place in West Sacramento I went to to help me measure for shims.

https://www.drive-lines.com/dlssac.com/index.html

They'll either build you a CV Drive shaft, or you can just get opinions on the shim sizes.

They have the steel ones.

I personally removed the drop t case kit, and got the CV driveshaft and shims to point the Transfer Case straight back. But you're right that it's around $300 - $400 +/- (going from memory - might have been high 2's even)

Then after I was sure the vibration was better, we took the shims out and relocated the spring perches to match where the rear end was pointing.

 

[elkgroveguy]

I talked to Drive Line services yesterday.
For a new CV rear drive shaft, new Transfer Case yoke, and CA sales tax,
I would be looking at $395.00
Not a bad price but I'm just going to put the old springs in for now and call it good.
I would rather have a 1" less lift in the back of the jeep and $400 in my pocket.
If Iam going to buy a new drive shaft I would rather wait until I stretch the wheel base a little and buy it then.
I would like to push the rear axle back a couple inches and run some longer more flexible springs anyway.

 

[73CJ]

Take a look at Tom Woods

Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist

He gets $320 plus free shipping

A CV shaft ended all my DS problems just bite the bullet and do it right if you want to be lifted.

I got tired of replacing them all the time even with a “lifetime” warranty on the U-joints.