13 replies to this topic

[colinu]

I decided to replace my standard diff with an X-pin one from Minispares (reusing my old output shafts). First time I've assembled a diff and was surprised how straight forward it was... until I tried to turn the output shafts once assembled. I had expected to it to spin very smoothly/quietly like my old diff did, but it's very noisey/notchy (can feel every tooth engage as you spin it). On first assembly I could spin it by hand with great difficult and it would bind at one point in the cycle. Dismantled it and felt like the bronze washers were catching a little on the planets... so I used some Barkeepers Friend to cut/match each washer to its planet. That got rid of the binding point in the cycle - I can now spin the whole cage (hold the ouput shafts vertically, spin the cage by hand and it runs for a few cycles)... but it's still noisey/notchy (sounds a bit like an old football rattle).

Is that normal? I'm a bit worried that if I do mate it up to the box "bad things" will happen when I put power through it.

If it's not normal then what's the cause, and how should I fix it (maybe new output shafts... hopefully ones whose teeth match the planets a bit better)?
I'm pretty sure the thrust washers on the output shafts aren't the cause... I used one from the old diff (would have used the other too but I've mislaid it!), and one from the new kit which was the same thickness as the used one (a tad under 34thou). Even before I bolted the crownwheel in place the "problem" can still be felt/heard.

Cheers,
Colin.

Edited by colinu, 28 August 2010 - 07:43 AM.

[Guess-Works.com]

That's unusual, especially for a MS evolution x-pin....

However, if you can turn the output shaft then don't worry too much, the engine has considerably more torque that you have to turn the diff.

[colinu]

"Unusual"... exactly what I thought, hence my concern. So you think that even though it spins freely but sounds like a football rattle it should be OK to use?
I'll try to post a video of it tomorrow once I find my video camera (12:30am here in the USA... not a good time to go rummaging and waking up the wife & kids!).

Cheers,
Colin.

[colinu]

OK, I've uploaded a short video to YouTube. It shows the diff being turned by hand in three positions (diff fully assembled but bolts not fully torqued up yet).
1 - Diff in normal horizontal position... hear the sound? (sounds/feels a bit like turning the chuck on a hammer drill by hand)
2 - Diff vertical and held by the "bottom" output shaft (i.e. pressure pushing all the cogs together) - noisey!
2 - Diff vertical and held by the "top" output shaft (i.e. no pressure pushing the assembly together)... very little noise/vibration.

Find the video here... Noisey x-pin diff assembly

Cheers,
Colin.

Edited by colinu, 28 August 2010 - 06:32 PM.

[Guess-Works.com]

what's it like with the bolts torqued up ?

[colinu]

Was about to torque the bolts up... then thought "how do I hold the cage tight enough to torque the bolts up to 60 lb/ft?". Any suggestions? Do I need to asemble it back into the housing/box, lock the gears (select 1st+4th) then torque up, or is there a simpler bench top method? Right now (as in the video) they are sitting at 30lb/ft.

I'm tempted to dismantle (again) and try with just two of the planets, then the ohter two... to try and eliminate if there's a "bad" one in there... might even try with the two old planets from the original standard cage (if they sound/feel rough then could it be mis-tolerance on the new cage?).

[Turbo Nick]

i'm sure i remeber hearing about people having an issue with the fibre washers supplied with these 4 pins and fitting the old ones cured the problem. something about them being too thick?

Edited by bud666, 28 August 2010 - 08:28 PM.

[Pauly]

To torque the crown wheel I whack the crown wheel in the vice vertical. Wont do no damage, make sure its tight so it wont slip in the jaws though.

Did you use new fibre washers in the kit? You might find when you torque the crown wheel it will pull down on the output shafts and might lock it up. Happened with mine and to solve it I just re-used the original washers, they where in useable condition.

But if the crown wheel is only on finger tight then the output shafts are not pulled in, so you might lose the rattly noise when its torqued up.

Edited by Pauly, 28 August 2010 - 08:38 PM.

[Guess-Works.com]

Fortunately I have a vice which is big enough to hold the diff unit horizontal, you can hold it by the crown wheel but be careful the metal is hard, but brittle, and if it slips you can break a tooth..

Bottom line, if it turns by hand when torqued up it'll be fine, it'll just be the fresh machining of the pinions which will soon bed in, even if it's difficult to turn by hand, grip one of the output shafts in a vice and turn the diff by the crown wheel, again if you can turn it then it'll be fine... it's only when it's locked solid there would be a potential problem, as it would then be acting more like an LSD.. which it is not designed to do...

[colinu]

Sorry for the delay in getting back to your replies (I was camping over the weekend )...

Big vice... been meaning to get one for a while - now I have a good excuse

The fiber thrust washers are not too think. If memory serves me right the thick ones supplied "by mistake" a while back were 45thou thick. I measured (micrometer) my new ones... they are 34thou and 37thou (compared to my old ones at 32thou). I was tempted to reuse my old ones, but seem to have mislaid one of them

To investigate I tired fitting only two planets at a time in the new cage to see if I could understand where the noise/notchyness was comining from (e.g. could it be a "bad" planet)... any combo I tried made no diference. I also tried the two old planets + old bronze thrsts + old pin in the new cage... only gave a little less noise/notchyness (unlike when fitted to my old single pin cage which was smooth and wisper quite). Maybe it's just cage tolerance that's causing this??? ... and hopefully they'll bed in with time rather than do something natsy inside the box!
New cage is back together again with all the new planets fitted. I won't get a chance to torque it up and see how/if it spins until the weekend... I'll keep you posted.

In the meantime I'll probably drop Minispares an email asking for their comments (e.g. has anyone else reported anything similar to them).

[cooperrodeo]

I have just installed a cross pin diff and initially I was a bit concerned about the notchiness when it was on the bench. This occurs if you rotate the output shaft when pushed in as in the first part of the video. It is also worst if the output shafts are not properly aligned (as is the case in the first part of the video). It is much better if the output shaft is pulled out as in the second part of the video. In normal operation the output shafts will always be pushed out.

When installed in the diff housing with the output covers correctly aligned, so they are not putting a lateral force on the output shafts, everything seems perfectly OK. I can't hear any noise from it above the rest of the racket from the engine so I am quite happy with it and I do not think there is any problem at all.

[colinu]

Cooperrodeo - nice to know I'm not the only one with this concern. Even better to hear that it shouldn't be a problem

[colinu]

Cooperrodeo - nice to know I'm not the only one with this concern. Even better to hear that it shouldn't be a problem

[colinu]

I got a reply from Minispares who said what I'm seeing is fairly normal and should bed in. Phew!