Reconditioned Diff Whine

[Stuart+2]

Hello fellow forum members,

Recently I had my diff rebuilt by someone recommended to me by a Lotus specialist. I pulled it out, etc but gave it to him to set the diff centre up. This included a new crownwheel & pinion being imported from the UK as well as many other parts.

The problem is that the diff is far from quiet. It used to whine at around 80kph (50mph) but now it starts at about 40 kph on light throttle. Its annoying as this was an expensive repair and all bearings, etc were replaced.

It doesn't appear to be getting better. I replaced the oil after 300 miles and it had visible matal flakes, but I expected that. I included a synthetic additive in the new oil, but no change. I'm not sure whether I have a problem or not. The diff should be quiet in my view after a rebuild. I haven't taken it back yet as I wanted to be armed with more information. And its not a pleasant job removing the diff again so soon.

Any advice will be much appreciated.

Cheers,

[Tonyw]

Stuart,

A whine would indicate to me that the set up is not correct, a few bits of metal may be normal but to be honest I would be worried if I saw them.

Tony W

[rgh0]

A diff rebuilt by a specialist with new crown wheel and pinion should not whine. Take it back, demonstrate the problem and get it done again properly.

cheers
Rohan

[Panda]

Hi Stuart,

Definitely not acceptable, take it back. I have used Craft differentials at Holroyd (near Parramatta) and also Laings diffs at Hornsby. Both very good and Laings particularly well priced for your next time!
cheers
Alan P

[robertverhey]

I've used one of those two sydney reconditioners hmmmm wasn't really happy with mine...a bit whiney. More off-line if you wish

[Jeff@Jae]

The usual errors are not enough carrier bearing preload and sometimes not using a new crush sleeve to set the pinion bearing preload.

[jk952]

I had the same problem, one of the few things I outsourced. Mine was(is) a 3.55 that showed little wear when I took it in, and I provided new shafts and bearings. I also provided a new crush sleev but he didn't use one of them. Mine whines most noticeably at about 40 mph, then less so, or is downed out by road noise. He said he "blued" in the gears to verify contact area as should be done.
Wish I had done it myself now....
I was wondering if they had wacked on the output shafts to install with the bearings into the alum. housings that it would have damaged the ball races thus creating a whine?

Thanks for the tips, for whenever I take it out again! Was driving it for a while to see if it would wear in. Haven't checked for bits in the oil but also has very few miles.


Jack

[jk952]

I had the same problem, one of the few things I outsourced. Mine was(is) a 3.55 that showed little wear when I took it in, and I provided new shafts and bearings. I also provided a new crush sleeve but he didn't use one of them. Mine whines most noticeably at about 40 mph, then less so, or is downed out by road noise. He said he "blued" in the gears to verify contact area as should be done.
Wish I had done it myself now....
I was wondering if they had wacked on the output shafts to install with the bearings into the alum. housings that it would have damaged the ball races thus creating a whine?

Thanks for the tips, for whenever I take it out again! Was driving it for a while to see if it would wear in. Haven't checked for bits in the oil but also has very few miles.


Jack

[Tonyw]

Gent's,

From my experience the whine relates to how well the crown wheel and pinion are meshed, a properly meshed C&P will not be noisy, if the bearings have been in any way damaged they will prematurely fail and you will hear a low growl type of noise and generally not a whine. If it whines now it will always whine it will not "run in" "wear in" and dissapear.

Putting bearing blue on the crown wheel and revolving the pinion simply shows where the C&P is in contact and therefore how well it is meshed. These can be tricky to do but again from memory because it has been a long long time since I wrenched spanners for a living once you have a set pattern on the C&P it will generally always be noisy.

Tonyw

[jk952]

Well since it is repair season is here, slid the diff. out, had to do other things anyway. Diff. still was whining at about 40 mph power on only, lift off -quiet. Appears that the pinion catching mostly on the tip of the crown wheel and maybe binding the other side too, seemed way too tight. But is that all?
Don't want to take back to chap that worked on it, as I can screw it up myself, then at least I know what I did.


Anyone know the pinion bearings part no.('s)by any mfg. for cross ref.- haven't found in archive or books, be nice to buy before I dismantle further. Local shops tend not to have old vehicle data anymore. Have the crush sleeve. The crown brgs are timken uk no. 48510.

Jack

[Panda]

Hi Jack,
Pinion bearing cup is SKF K-M88011/15
Pinion bearing cone is SKF K-M88043/11

Courtesy of Paul Robinshaw's book

cheers

Alan P.

[Quart Meg Miles]

My 3.9 screeched when warm (for three years) but when I rebuilt it this year I could only find slight markings on one pinion bearing. Set it all up again with new bearings and crush washer, got a good blue mesh, and now no more screech.

I can't hear any whine as I fitted sound proofing above the diff in the V of the chassis and I can hardly hear the exhaust either! That's a cheaper solution to getting rid of whine though rather fiddly.

[robertverhey]

Meg..sound proofing above the diff.....do tell more....what sort of material, where and how installed? Robert

[vstibbard]

Ive just had diff rebuilt with new centres in Hornsby, guy does lots of historic cortinas and races himself. He did a diff for me in 09 that has 20000+ miles on it and quiet.
PM if you want details.

[jk952]

Vstibbard, thanks, but that is a tad too far away for me!
Turning it on the bench while doing nothing really I noticed it had correct clearance in one area but seemed tighter in another position; I had spot checked a few gear contact points not the entire crown. To verify if real or imagination, put on the dial indicator checking backlash on again and sure enough something is not rotating true. Been out of town on business so will get back to it on the w/e.
Jack