I just got a new driveshaft bearing and the housing for it for my '91 740. Along with that I had a transmission mount that was cracked welded back together. Before this was fixed the car would make a strange noise shifting from 1st to 2nd gear. It was sort of like a fast vibration, like a machine gun I suppose, but it only lasted for about 3 or 4 "shots"? I can't think as to what it could be, seeing as how I thought that I had just fixed the prior source of the noise. But it's still happening. Does anyone have any idea what this could be? Any help would be appreciated! Thank you.

 

that knock-knock-knock sound often IS the drive shaft bearing... other candidates could be a worn spring seat, a bad thrust or panhard bushing

see the drawings in post 12 on this thread...
https://volvoforums.com/forum/volvo-...g-69937/page2/

the second drawing, part #21 is the lower seat, this is basically a rubber cushion the spring sits on. the first drawing, parts 32,33,35,36 are the thrust rod bushings, and 13, 14 are the panhard rod bushings. the smaller thrust bushings (32,35) rarely wear out but the bigger ones can.

btw, I recommend using Volvo brand original rubber bushings and not poly... they lasted 20 years. poly bushings will give a harsher, noisier ride, and are likely to wear out sooner than the OEM rubber. if you DO use poly bushings, use SuperPro, accept no substitutes... the noname chinese stuff in particular is mostly junk.

 

It's been a while since I was able to get to the computer. It's more like a shudder sound, and I was told that it's because my transmission fluid is old and so my transmission is slipping a little when it shifts? I'm going to try changing out my fluid quart by quart as soon as I can get my hands on some, and I hope that helps a little. any thoughts?

 

1. to change the ATF on a 240/740/940, get the transmission nice and warm (drive 10 miles or so, it warms up slower than the engine), then check your transmission fluid level while the engine is idling in neutral/park.... we'll assume it was full, if not, adjust the amount in this next step upwards by however much it was low...
   
2. Now, remove the plug from the bottom of the tranny and dump it into a clean pan. after its finished draining (let it drip for hours), put the plug back in, and measure what drained out. use a clean transmission funnel, put the skinny end into the dip stick hole, and add the same amount of fresh ATF (adjust amount upwards if it was low before you started).
   
3. now, disconnect the UPPER transmission cooler line from the right side of the radiator, attach a suitable sized clear hose a few feet long to the radiator nipple with a clamp, and run this hose into your drain pan. start the car, let it idle and watch the drainage, stop the engine when it runs clear. measure how much came out, and add this much to the transmission via the funnel.
   
4. repeat step 3 until it runs clear. you'll need at least 8 quarts, maybe 12.
   
5. replace the transmission cooler line. replace the transmission dip stick. start car, let idle a few minutes, check the dipstick, it should have ATF up to the 'cold' marks if you measured correctly. if its too low, add more until its good. now test drive 5-10 miles and verify its to the top line on the 'hot' side, add more ATF until it is.

I just use generic dex/merc III red ATF, many people say you should use synthetic for best results, I dunno, synthetic didn't even exist when these transmissions were designed (its actually a Borg Warner transmission design from the late 70s that was adapted by Toyota's Aisin-Warner factory in the early 80s.... AW70/71/72 transmissions are versions of the Toyota A43D family, as used in a number of 80s higher performance Toyota RWD cars and trucks, like the Supra Turbos of the early 80s.


edit; emphasis on CLEAN when you do this. wipe off the end of the dipstick tube before removing the stick. clean the hose fitting before removing the hose. use a spray degreaser on the area around the plug under the tranny before removing the plug. YOU DO NOT WANT EVEN A SINGLE GRAIN OF GRIT TO GET IN THERE.

 

I have an uncle that's been a mechanic for years who says he'll help me do it. But in the event I do end up doing it myself, at least now I know what I'm doing! Thank you for that!