Rebuilding an LSD?

[Julian Thompson]

English Axle LSD into spangly new alloy casing..

 

..requires a full LSD rebuild.

 

Not stripped it down yet and am teetering on getting a pro locally to do it but I wonder how hard it can be?

 

Realistically is one able to DIY an LSD rebuild with some common sense and mechanical savvy or is there a "black art" to it?

 

Apparantly the use of the alloy case means I must cook the case in the oven (make sure the wife is out then - I don't think she'd appreciate that 😬) before assembly and do some extra shimming somewhere to cope with additional expansion?

 

 

[Julian Thompson]

Guess that's a no then 😬

 

Dave Brooks here we come? 😬

[Sheds Moderator]

I don't think it's child's play. How do you set up the ramp angles without expert advice? Gear meshing setup on a std diff isn't easy either, you need engineers blue etc. I'd be happy to have a go given a manual but you won't get one. ☹️

[Willie.]

JT,

 

Is the 'cooking' just a gentle heating, so the casing is at its working/heated size?

 

I've never built an English diff, but have LSD'd my De Dion (Sierra) diff...which was a piece of cake. The English is more difficult.

 

As boss says, its the gear meshing that's tricky. On your old diff, use some engineers blue to determine where abouts the gears are meshing (Inside, outside or middle of crown wheel) and then measure the back lash. Setup a clock/dial gauge, clamp the pinion and measure the backlash in the crown wheel. Take 3 meaurements around it (They should be almost identical).

 

The tricky bit really is the pinion. You may need a big, deep socket to torque it up. It has a crushing tube/spacer...and the aim of the game is to gradually pull it down til it's in the correct position (You can only tighten, so go slowly). You'll need to pull it down until it's nearly right...then fit your crownwheel so its in the correct fore/aft position (Shim it to stop it sliding, and put the U brackets on to hold it). You can now use the engineers blue again, and keep tightening the pinion bolt until the pinion is running in its original position on the crown wheel. (There is likely a torque figure for the pinion bolt, but be very careful...its easy to overshoot, and then you'll need a new crushable spacer).

 

Next you need to adjust the sideways position of the crownwheel. That is what determines the backlash. On the Sierra diff its dead easy, just turning the side nuts...but on English axles its trickier as you've to do it with the shims. Obviously you need to get your clock/dial gauge out again, and you're aiming to get the same backlash as before. Once you're there...you've to fit equal extra shims either side to preload it as necessary.

 

I'd advise getting it out and having a look at it. You know what needs done, and with the diff in your hands you'll be able to decide if its your kind of job or not.

 

Just my 2p. I'm sitting in the house feeling miserable...so that's my days work done

 

Willie

[Julian Thompson]

OK chaps that's mega, mega helpful.

 

Two things to say then.

 

Firstly, yes, the heating is to allow the bearings to be pressed home into the casting without scraping the alloy and creating swarf round the back of them. It is indeed just supposed to be a gentle heating.

 

Secondly, I have been told on the alloy case to make a NON crushable crush spacer on the lathe rather than using a crushing one. Can't remember why the guy told me that (he did tell me a good reason but I forgot )

 

.....does all sound a little tricky though!

[Willie.]

I have been told on the alloy case to make a NON crushable crush spacer on the lathe rather than using a crushing one.

 

That'll be the super lightweight alloy casing then? 😬

 

Willie

[Julian Thompson]

You got it !

 

You've done this before, haven't you OL? 😬

 

Why DID he tell me to make the non crushable crush washer thingy?

[jerrypike]

julian

 

even the race mechanic who does all the work on my car shipped the diff. for its rebuild / ratio change.

 

but let us know how it goes 😬

how many spanners in the haynes manual

🤔

 

 

jerry

[Willie.]

Julian,

 

If you remember the reason (For a solid spacer), I'd be interested to know.

 

Could it be so you could get decent torque on the pinion nut (Without affecting the position?)

 

Never heard of people doing that before. You've got me intrigued now.

 

Willie

[Julian Thompson]

Spanners rating 😳 - not sure. Will tell you how it looks when I get it in bits on the bench!!

 

I just spoke to the suppliers of the casing. The reason we need a non crushable spacer is that on high power applications you get "pinion creep" if you use the standard crush spacer....

 

....At the moment all this is as clear as mud but I'm hoping that it will *idea* when I finally get to see it.

 

Will post some pictures and link them from this thread so you can all have a laugh at me 😬