6 replies to this topic

[RawlinsGTR]

Hi all,

 

My rear differential cover was damaged a while ago, and I don't want to have to replace the entire gearbox.

 

I know that the rear diff cover and gearbox casing are essentially 'matched' since the bore for the differential roller bearings is drilled with them attached to each other.

 

I was wondering, if I could find a spare rear diff cover that was a close 'match' to my gearbox casing (i.e. the lip on the bearing face between the two was not massive), would this be an possible thing to do?

 

Or are the tolerances that critical? I would assume that it would be okay since the casings are aluminium and will probably flex a small amount when clamping round the differential bearings anyway, but I just wanted to see if anyone had any more knowledge!

 

Thanks in advance,

Simon

Edited by RawlinsGTR, 04 August 2016 - 02:40 PM.

[Guess-Works.com]

you're never going to get a 100% match, but when has that stopped anyone from doing this....

The things which you need to watch for are...

The bearing hole lining up, This is critical... If they don't then there's a possibility that the differential will run slightly out of true with the mainshaft and pinion... this will accelerate wear on the  two components... and may make it noisy.

The sides being true... If there's a step between the cover and the gearbox, this will compromise the thrust load on the differential bearings, and could allow the diff to more side to side when under load and on run down, especially the transition between the two, again accelerating wear on the crownwheel and pinion, but also the bearings,

Finally, it'll probably piss oil because you can't get a proper seal.

 

As mentioned above... but when has that stopped anyone ?

I have matched odd covers to other boxes myself, especially for the hybrid boxes I build, however most need a little fettling and machining to get correct, and that's only possible with the case stripped and on the bench/mill/line bore etc etc etc

[ACDodd]

Yes it is possible I have saved a few cases myself over the years. As Guessworks has already said fettling is usual and have a large supply of used housings is a must in order to find a close match.
It can be done but succes is limited unless dimensions are checked and managed accordingly. This is certainly not a just get another housing and bolt it on and it'll be fine process.

Ac

Edited by ACDodd, 04 August 2016 - 04:23 PM.

[RawlinsGTR]

I thought this might be the case (if you'll pardon the pun), thanks both of you.

 

I've had trouble getting this box to seal already so I didn't want to just steam ahead without knowing the full story.

 

Looks like I'll be needing to find a replacement.

 

Simon

[Guess-Works.com]

Replacement cases available... clean and ready to build into... £50+shipping+vat

 

oh... I may have to put a forsale notice up in the for sale section 

[Spider]

I've managed to get quite a few to match up, successfully.

 

On top of the suggestions from Guessworks and AC here, I remove the two Dowel Pins, it gives a bit more freedom. The Bearings will do WAY more for locating the cap 'up and down' that the small dowels will, the 'side to side' is located by the diff side covers. The Dowels were only fitted in the factory to hold the parts relative to each other for machining.

 

I'll add that I have had a few that lined up in every other way, but the shifter shaft, which, as Guessworks has pointed out, will leak badly. On ones I've had like this, I machine this hole out about 2 - 3 mm bigger, press in a bush, then off set bore it to be on alignment. I think I've got some photos of this on the office PC.

[Spider]

I think I've got some photos of this on the office PC.

 

 

A little hard to see completely here, but the Bore for the Shifter Shaft has been off set to line up with the Shaft. No leaky Oil