Sometimes on my 1989 740 I hear a sound from underneath the car when i shift from park to drive that sounds like something banging against something. The sound also occurs when driving down the road when i depress the gas pedal or release the gas pedal.

When i push up on the driveshaft the transmission moves...it's that normal or a sign of a bad transmission mount?

Could a bad mount be the cause of the noise or should i look elsewhere

 

You have to examine the whole driveline, a bad driveshaft u joint will do what you describe, my choice, but it could be something else like a flex disk... Mark that driveshaft if you remove it as the parts are balanced and have to go back the way they were to avoid vibration.

 

only stickshift manuals have a flexdisk, automatics have u-joints instead.


if the tranny itself is moving more than the tiniest amount, then yeah, the tranny mount is giong bad. best to replace the 2 engine mounts at the same time, as all 3 work together.

 

why don't YOU take a look at the tranny mount and tell US if it's bad or not!?

from my position here at the keyboard I guess that it IS.

 

I think they ALL have U joints...

 

they do, but the sticks have one flex disk aka giubo at the back of the transmission, then a central and rear U joint. the automatics have 3 U joints.

 

while we are talking about U joints.... can I threadjack and ask if there are REALLY three different size ujoints that could be used at the FRONT of a 240 driveshaft? 740/940 also should have similar issue.


IPD says it could be ANY of the following:

1.) 2-5/8"
2.) 3"
3.) 3-3/16"

But Oreilly (wayyy less reliable), asks me to chose if its the front, middle, or rear ujoint for my year. I chose FRONT and it gave me the option of:

1.) 2.931"
2.) 2.940"

I am not going to even bother calculating what 9 thousandths of an inch works out to, but it sure isn't the difference between the 3 IPD lists.

I just went ahead and took a gamble that it's the 3" and have that one coming my way. Is measuring the actual ujoint in my car REALLY the only way to be sure?


One result on search said:

4A5512 2 7/16" dia. yoke is 2 5/8" diameter

4A5514 3" dia. yoke is 3 1/4" diameter

4A5512 3 3/16" dia. yoke is 3 1/2" diameter


Spoonfed me the answer please. Search is coming up with it is contingent upon driveshaft diameter. Please confirm, deny, or provide input! Thanks.

 

sounds like you need a copy of VADIS, the circa 2003 Volvo parts catalog software which has all the parts pages for the various older models, and lists the multiple choice options and definining characteristics. yes, its quite likely there could be 3 different sized drive shafts in the same year/model car, they used what they had on hand.

 

I lost my copy of international VADIS years ago. Anybody! PM me if you can send me a copy. Thanks. My old computer with it on it is long dead too.

It was nice to have for part numbers and for reference.

IPD knows what they are talking about. I, however, haven't done ujoints in these cars for years but I DO recall learning that driveshaft size might be somewhat random. Weird.

My poor 240 makes all sorts of STRANGE VIBRATIONS (in Fear and Loathing voice) due to a totally blown ujoint. One of the corners has lost all the needles and is clunking real loud and hard right now.