Rear end shudder

[jarhead]

My car is finally road worthy for more than a few weeks duration. Prior to that it was sitting for years and not sure what was done by the PO. When I back up in reverse or start forward in first gear, the rear end vibrates something fierce. The whole car shakes until the car is up to about 5-10mph. After that it's fine. It will occasionally do it while at too low rpm for the gear.

I have no clue as to what was done rear of the crankshaft as far as drive train is concerned. Tranny(not transgender) and differential have new fluids. Feels like flywheel chatter. Should I be concerned?

[Gregs672000]

Wondering about Ujoints, securing bolts, etc. I assume the engine is not the issue and it will rev smoothly out of gear? I've experience vibration from loose drive shaft to diff bolts (and on my U20 where the drive shaft bolts to the trans... I use locktite now!)

[notoptoy]

My first thought was U-Joint issues as well.

[jarhead]

Defininately not an engine revving issue. I'll check drive shave connections. Thanks.

[Linda]

The tranny mount can loosen up also.

Linda

[dbrick]

Does it matter how hard you accelerate?. Trying to see if it's speed or torque related. Generally, but not always, driveshaft vibrations are in the 40-45 mph range. Tight ujoint is a good bet or a dragging brake shoe.
What if you stop on a downhill and let it coast up to speed? If it vibrates, that leads me to bearings or brakes and would eliminate clutch/torque issues, and if it was a chattering clutch or similar, conversely it should be far worse trying to start out up hill with the extra torque needed.

[jarhead]

It's a low speed torque issue. Goes away completely at high speed. It is not present with clutch disengaged.

[AidanDawn2000]

Is the parking break completely disengaged? Maybe try jacking up the back and giving the wheels a turn by hand.

[Gregs672000]

Is the clutch in the process of engaging while this shuddering occurs? Or will it do it when at slow speed or low rpm but with the clutch fully engaged and as you accelerate?

If its during engagement, i think it could just be years of sitting with the clutch dormant, and it just may clear with use. If not, then one wonders what's loose or broken, cause something's not right! Got to go through the whole drivetrain and inspect everything if the shudder is bad... Might get worse and leave you somewhere! My 2c!

[jarhead]

It happens mostly with clutch engagement but have experienced it with slow speed. I need to get it on a lift. Thanks for all the input.

[garth]

It's a low speed torque issue. Goes away completely at high speed. It is not present with clutch disengaged.

What you describe is a low speed unbalance that diminishes with engine revs but is connected to clutch engagement.

I will go out on a limb here but that sounds like a transmission bearing problem if you have confirmed engine and transmission mounts and u joints are solid.

I had a near identical problem last year except the vibration was not very pronounced but had a low squeal when clutch was released in either 1rst or reverse. I went through a whole lot of troubleshooting and advice gathering to isolate the problem. The squeal and vibration was intermittent and usually occurred on cold start. After eliminating all the less expensive causes I pulled the transmission and found several bearings at wear limits so replaced all bearings plus the clutch throw out. I had the transmission and bearing work done by a transmission specialist. Now the transmission is very quiet at all speeds and loading and hopefully good for the next 100,000 miles.

[msampsel]

100,000 miles is truly exuberant optimism!
Maybe the Canucks will win the Stanley cup this year too! Well we can all hope for the 100,000 miles anyway!

[dbrick]

I should have a driveshaft around and I have U joints if you cant find any. Vendors had a price war/sale going on Ebay for clutch kits a while back, great parts great price., might be worth just doing it all while it's out and be done with it.
If you want to try the shotgun approach, we could probably scare up a known good 4 speed somewhere on this coast or convert to 5 speed.

[jarhead]

I should have a driveshaft around and I have U joints if you cant find any. Vendors had a price war/sale going on Ebay for clutch kits a while back, great parts great price., might be worth just doing it all while it's out and be done with it.
If you want to try the shotgun approach, we could probably scare up a known good 4 speed somewhere on this coast or convert to 5 speed.

And a U20 swap while we're at it!

[ed B]

Just for the heck of it, check your motor mounts as well.