Judder on Takeoff/ Driveshaft Carrier Bearing/ Mounts
 

Trying to troubleshoot a judder in reverse (M46).

Some is probably attributable to the cracked front crossmember but I just checked the driveshaft and found the center carrier looked suspect. Isn't that rubber collar supposed to be further forward? Set into the bearing sleeve?

Also, the driveshaft appeared to be able to move too easily in the center carrier. Should I be able to move the driveshaft around there with finger pressure?

(photos from the rear)

They are supposed to be soft, I tried shimming one up solid, and almost broke teeth on the test drive it vibrated so bad.

I would check the rear axle bushings. Really worn bushings would cause a shudder.

Just as stated above, the bushing should be soft to the touch. The drive shaft should move around in the bushing, almost like there is to much play in it. There should also be a spring in the bushing.

Made good progress in solving reverse judder (M46).

Removed driveshaft to replace suspected center U-joint. BUT: U-joints tested good. Smooth movement, no binding, no play, so I removed the plugs and greased them (temporarily installing 1/4" x 28 zerk fittings), and reinstalled driveshaft.

Rear of car appears to sag, springs look tired. Rear spring replacement planned for the future. Meantime I raised the position of the center bearing carrier 1/4" by inserting three 5/16" washers per side, between the chassis bracket and the brg carrier, bolt thru.

This lessened the reverse judder by approx. 50%. Might try shimming more (for 1/2" total) but first want to try replacing the soft panhard rod bushing, and trans mount.

I spent a lot of time and energy fixing rear sag before I figured out my front springs were actually elongated.
If you park next to other similar cars,and your nose is consistently an inch or two higher, it's the front you need to work on.

That's interesting. How do the front springs get elongated?

Best theory I've heard is the wire untwists over time, leaving you with a longer spring of a soft rate.

Wonder why it would affect the fronts and not the rear?

In my quest to fix the reverse (and to a lesser extent) and forward starting-off judder, I replaced the LH motor mount and the trans mount.

It was getting especially bad; seemed to be combining with a distinct thud-thud-thud at times.

To recap: Replacing the front crossmember with the newer reinforced style (and more importantly, non-cracked), and shimming the driveshaft carrier upwards helped some, but problem persisted, and was getting worse again. Mounts were the next items to replace.

Off to a great start! Removing the LH motor mount was easier than I remembered! Only had to remove the (easier) bottom nut, and it came right out! :p O, this is going to be a piece of cake! Ha-ha, I'll be done before dinner! Hey, wait a minute:::::::::: what holds the motor mount to the motor????????????
http://i84.photobucket.com/albums/k3...s/P1010007.jpg
THAT would explain the thud-thud-thudding on takeoff. 700+ pounds of engine doing the Riverdance on that poor mount.

Well, I really did end up getting the rest out:
http://i84.photobucket.com/albums/k3...s/P1010008.jpg

Old (reconstructed) vs. new:
http://i84.photobucket.com/albums/k3...s/P1010009.jpg

Think this is getting pretty common: Rubber is stamped "Volvo Germany" but the box is labeled "Made in China" :( Wonder which is true? Note the date on the label: 9/3/2013. I ordered it on 8/30/2013. Talk about Just-In-Time supply chain!!! I call it Made-To-Order!!! This is from Rock Auto, by the way. $3.52. We'll see how long it lasts!
http://i84.photobucket.com/albums/k3...s/P1010010.jpg

I didn't get a chance to test it extravagantly but a quick launch backing upwards out of the driveway, turning around and backing back down showed less drama starting off, both back and front. Didn't want to push my luck because:::::

Of course there is a casualty from this exercise; there always is.

I noticed small drips of coolant down off the bellhousing. Following the trail upwards it appears to be coming from the flange at the rear of the head that the oil cooler hose attaches to. :mad:

Maybe I crunched that flange too hard against the firewall during my efforts to raise the engine and tranny to change the mounts? I had a cherry picker pulling the front of the engine, and a floor jack under the trans at the same time.

What are my options here?