89 740 bad rear differential

nisan17 · Post by **nisan17** » 06 Jan 2012, 21:15

I recently had a reputable mechanic shop look at my differential because of the hum/whine it is having during hwy speeds. They said the pinion seal leak caused the bearings to become bad and there was shavings in the lube. Couple questions: can I just change the bearings and is that a big job(I can buy a bearing/seal kit fairly cheap) Can I just put a pinion seal on there and keep fresh clean synthetic lube in there. I would like to nurse it till I can get a used axle if I have to. I plan on giving the car to my son who doesn't drive much.

It is a non locking, 4:10 geared, non abs diff. Any advice would be greatly appreciated.

Thank you in advance,

Post by **billofdurham** » 07 Jan 2012, 10:53

How much time do you want to spend on this? To strip and rebuild the diff is a 5 hour job, for a trained mechanic. To replace the pinion oil seal is 0.5 hours. If you are contemplating fitting another axle further down the line my advice would be to do the oil seal and refill with SAE80W-90 as specified by Volvo. In cold climates they specify SAE80. If you have been running with synthetic oil the change back to the heavier oil may reduce the hum.

Bill.

Post by **mikealder** » 07 Jan 2012, 11:59

If you are intending to replace the bearings you will need a bearing seperator/ puller, I used one of these http://www.machinemart.co.uk/shop/produ ... RC-bearing puller when I stipped the diff in my old 740 Turbo - Mike

nisan17 · Post by **nisan17** » 07 Jan 2012, 21:34

Thanks so much guys. One shop quoted me $1000 for a used axle w/o labor. Same shop wants $130(just part) for the pinion seal!

Post by **mikealder** » 08 Jan 2012, 03:23

If you do go down the junk yard route for a replacement diff make sure you take one of your own drive shafts to the yard, insert this in to the diff to make sure the drive splines are the same otherwise you might end up with a useless lump of metal when you get home.
Its around ten years ago since I rebuilt my 740 diff but the junk yard part I used was only £50 coupled with around 30 hours of work as I did wheel bearings and brakes at the same time as it was all in bits, quite easy to work on once you get it clean, a parts washer comes in real handy as the old oil in the diff stinks! - Mike

Kirby J · Post by **Kirby J** » 11 Jan 2012, 00:49

I had to replace the rear axle this summer for my 940-same cause- bad pinion seal-ruined rear end. I shopped around and got a complete rear axle assembly from a yard in Atlanta for about $200. Shipping was another $200. But I could not drive to Atlanta and back for that. Installation was about another $250. $750 was more than I wanted to put into my old car-but I could not replace it for that, so I spent the money. 30k miles later I am still happy with the car.

Kirby J 93 940 428k

Post by **precopster** » 11 Jan 2012, 03:58

When I owned a 740 turbo I bought a friction reducing treatment for all my fluids so I went about draining all the fluids and refilling with new before doing the treatment. Upon pulling the drain plug for the diff I couldn't believe how much moisture was in there with the gear oil. It was like cappuccino!!

The diff oil is probably the most neglected oil on a RWD car and should be changed at least every 5 years.