Drivetrain Vibes

[EricM]

Ok I have a 72 Jimmy with 6" lift out back and and 4" in front. I recently put a 14FF w/gov-loc in the rear and D60 in the front. Then I swapped the rear yoke on the T-case to accept a 1350 joint and had a custom drive shaft made for the rear. Now I have a new vibe. It sounds like gears clattering. When I get up to about 40mph and let off the gas it does this then when I ease back onto the gas same thing. Igoes away with constant throttle pressure. Any ideas what it could be? OH yeah I have an SM465 which was rebuilt about 2 years ago so I doubt it's that. And the angle from the T-case yoke is within a couple degrees of the yoke on the rear end. I never had this vibe running the stock shaft with a conversion joint. What should the yoke on the rear of a 205 be torqed to? I torqed it to 95ft/lbs could this be causing the noise? Please help I'm stumped.

 

[ErikH]

I recently installed new rear springs and a new shaft. And I ended up with the same vibration problem... I discovered that the 2.5-degree shims placed under the springs, which nicely rotated the rear yoke up toward the t-case, were actually the cause of the bad vibes. With a simple shaft (with one u-joint on each end), the angle between the yoke and the shaft, on each end, have to be the SAME. I took the shims out, and the vibes disappeared. A better solution would have been to lower the t-case, but I didn't have the energy to do that.

Another solution would have been to install a shaft with a CV-joint or double u-joint on the t-case end. Those two joints would have cancelled-out the vibrations. But since I spent a couple-hundred bucks on the new shaft already, I didn't shell-out more to have it remade.

 

[harry]

How do you lower the t-case?

harry
69k5

 

[ErikH]

I was told to consider lowering the t-case by the guy at the drivetrain shop. He said it could be lowered by using homemade parts or using a kit, if one was available. I took a good look at the situation, and I could see that the rear crossmember could be lowered with longer bolts and a few spacers. I assumed the engine mounts had a bit of play in them to allow the few degrees of tilt.

Anyway, as I examined all the mounting location, I could see several areas of concern... I could see how the job would take 3 times as long and cost 3 times as much as originally estimated... which is why I abandoned the idea. The best solution to high drivetrain angles, as far as I can tell, is to install good (expensive)CV-joint driveshafts.

 

[bitchin4x4]

Well, I have the same noise going on. I have an 8" lift with no shims, other than the blocks which have a minor angle in them.

If it ain't broke, break it!<P ID="edit"><FONT class="small">Edited by bitchin4x4 on 08/17/01 02:01 PM.</FONT></P>

 

[bitchin4x4]

Well I checked mine out and it doesn't have any shims currently. So i am going to try the 2.5 degree shims.

If it ain't broke, break it!

 

[EricM]

I lowered my T-case by 1 inch but have the same vibration plus now the distributor hits the firewall. The T-case yoke and rear axle yoke are within 2deg. of each other which should be close enough so now I am wondering if the driveshaft was properly balanced. Iam going to take it in and have them re check it.

 

[bitchin4x4]

I've heard of others just getting the drive shaft filled with whatever would dapen the sounds. I believe it was some type of insulation.

We jacked it up at the shop and we definately heard the sound eminating from the rearend then traveled up to the transfercase and into the floorboards.

If it ain't broke, break it!