Anyone have an idea? My 89 740 has 290k on the clock with a M46 4spd with OVerdrive. I have isolated the whine to the rear end. Replaced the flex disk, midline bearing, and I run 75/90w synthetic in the rear. Always switched out every year. On the highway about 60mph thru 75 I hear a fairly high pitched whine..very smooth and speed dependent. This happens whether I am in gear or not. I'd just like to hear your ideas before I tear apart my rear end.... Many thanks...

 

sounds like either the carrier or pinion bearings...

 

290k, yeah, it's worn out...

 

Do you have any play in the pinion shaft. Try removing the drive shaft and check for play on the pinion before you pull the rear. Usually whining is due to gear misalignment or wear. Interesting that you change your gear oil every year and yet come up with this problem. Are you using a different type/brand of oil? It just seems to early for this to happen. I have 307K on mine and have only changed the rear oil ones at 10K miles. How does the gear oil smell , is it burnt?

 

Could be the output bearing of the trans/OD. Did you check the U-joints while you were there?
Not likely to be the differential.
Ed

 

Jagtoes, thanks. I use Mobil One Synthetic. I change it often just because I can, and its so easy on this car, drain plug and all. Doesn't smell burnt, and I pulled it again. The U-joints seemed fine...no play at all, but I will probably go ahead and replace those since they are so cheap. Just not looking forward to doing the rear. Pain. There is a Timken complete bearing rebuild kit online for a cheap price, but it doesn't come with a supply of four-letter words.....

 

Thanks Ed. I've had a lot of history with the M46 and OD. First in the car blew up and after that a "modification" was made...no problems since tho they can't seem to decide on what to put in it. I run synthetic Mobil One ATF in the winter while its cold, but in the summers here where average daily temp is about 75F I run non-detergent 30 weight. The OD had trouble engaging while hot, even with the updated apply-pistons. The 30 weight fixes that. I did replace the flex disk as mine was just about all eaten up, and the driveline felt smoother....but that whine is still loud and all the way from the rear.

 

From NCVOLVO940
sounds like either the carrier or pinion bearings...

Thanks guys.... Yeah, I was coming to this conclusion too. Sheesh, whats the world coming to? Can't drive a car 300k anymore????? Timken has a complete rebuild kit for $77.00. Now I just got to get dirty.

An interesting note: I read somewhere about the most reliable cars vs the cars with best longevity. Not a single car was on both lists. It seems that reliable is, but dies quick and Longevity means spinning wrenches. Glad I have my 740.

 

Now that I am committing to a rear rebuild, I need to identify which axle my car has, either the 1030 or 1045. Volvo tells me to look for a sticker (!) on the rear driver side axle housing but the car was undercoated, and sticker destroyed. VIN info for 1989 didn't include that info. Does anyone know another way?

 

All the cars are undercoated. It's there, left side, facing rearward.
You found a wealth of information along the way.
The rear end in the majority cars of any make is the most overlooked, under serviced part of the car. It lives it's life from assembly line to junk yard with out a thought from it's owners and without a problem. When they do make noise, they rarely quit or fail.
Ed

 

Ed7, thanks for the input. Car was just in your neck of the woods over the holidays rounding the corner to Grand Rapids.....

Off the cuff I would agree with you...most people don't know that the differential exists. But this is also my only car at the moment. Certifiable nastiness came and went in my life, so I need to keep up with this one. I will toot my own horn and say its the best looking 740 in the city, and I plan to keep it another 100 to 150k miles, so yes, I feel I should rebuild it. I don't need it coming apart when Im 300 or 600 miles from home. If you look at my other post "Identifying 700 half axles" i posted a link there that was quite helpful. But I will get back under there again and double check for the sticker. Seems Volvo got that one wrong...put the sticker where it gets coated over instead of inside the drivers door. Duh.

 

Thanks again to everyone. I have been listening to this thing sing along on the highway, and had recently been fixing a few other things. I am not worried about a quick catastrophic failure just yet.

Indeed it is the rear end. An older Volvo mechanic I trust at the dealer (he's the only one allowed to touch my car, and who owned several 700's himself) did confirm its the rear, both by driving, and with electronic "ears" of some sort while it was up on the rack.

A rebuild is out of the question to pay for, and I don't have that level of skill.

I am looking at swapping in a 3.73 rear from a yard here I can get for $175. The trick is getting one that will match the ABS option I have in this 89 car.

If anyone happens to know of a good used 3.54 92 or later 740/940 with ABS out there (not likely) please let me know.