Changing Diff - what parts will I need?

Sun Jul 15, 2007 9:05 am

My car is in for the diff to be changed at some point over the next few weeks, what other parts should we replace at the same time, i.e. diff mounting bush, etc? and what is likely to break / need to be replaced?

Thanks!

Sun Jul 15, 2007 10:20 am

Changing a diff involves disturbing nothing else, although you should remove the heatshields, adjust the length of the prop, and set the preload.
Diff bush is rubber and can deteriorate, but I've never had to change one.
What other parts should be replaced at the same time? I suppose you'll be part way towards removing the fuel tank and/or rear beam, so beam bushes, rear brake lines and fuel tank should at least be checked out.

Sun Jul 15, 2007 10:25 am

Brian,

Thanks for your reply.

Ok, I reckon one of my rear beam bushes is on it's way out - what else needs to be removed to change these?

Finally, don't suppose you saw my other post RE: top mounts? Is there supposed to be anything other than a thin gasket between the top mount and the body? Looking at what came off the LHS, there was also some kind of rubber cover around the round bit of the top mount, and over the shocker nut.

Thanks!

Sun Jul 15, 2007 10:40 am

FlashBastd wrote: Is there supposed to be anything other than a thin gasket between the top mount and the body? Looking at what came off the LHS, there was also some kind of rubber cover around the round bit of the top mount, and over the shocker nut

Just a paper gasket between the mount and arch. There should be the rubber dome over the inside, but I've no idea what they are for, other than to make things look neat and tidy. I've left out plenty.
Only the brackets underneath the beam bush nuts needs to be removed to allow the beam to drop a few inches to change the bushes, but the old bushes tend to seize solidly in place!
It'll help with all these jobs if the rear section of the exhaust is removed as well.

Sun Jul 15, 2007 1:42 pm

Brianmoooore wrote:although you should remove the heatshields, adjust the length of the prop, and set the preload.

How do you do that?

Sun Jul 15, 2007 2:31 pm

chu346 wrote:
Brianmoooore wrote:although you should remove the heatshields, adjust the length of the prop, and set the preload.
How do you do that?

adjust the length and bolt up the centre bearing carrier. Mark where it sits in the slots, loosen the bolts again and slide the carrier forwards about 5mm, hold it there and tighten the bolts.

Mon Jul 16, 2007 12:15 pm

Do any nuts, bolts, washers, etc. need to be replaced when changing the diff?

Mon Jul 16, 2007 2:15 pm

Do any nuts, bolts, washers, etc. need to be replaced when changing the diff?

I'm with you on that question. I'm about to do this project myself.

Mon Jul 16, 2007 9:30 pm

FlashBastd wrote:Do any nuts, bolts, washers, etc. need to be replaced when changing the diff?

In an ideal world, or the real one?

Tue Jul 17, 2007 6:36 am

Real one. I don't want to get it stripped down and then not be able to reassemble.

Tue Jul 17, 2007 7:44 am

I'am also looking at doing a diff swop and whilest were on the subject can you swop a small case diff 4.1 from my IS to a LSD from a 325 sport? is it a streight forward swop or would i need other bits?

Tue Jul 17, 2007 8:25 am

Straight swap. The two types of diff have different output shafts which result in the same overall width.

Tue Jul 17, 2007 7:51 pm

Sorry to jump in but do i need to adjust the length of the prop and set the preload if i'm swapping one type 188 diff for another type 188 ?

Tue Jul 17, 2007 8:16 pm

FlashBastd wrote:Do any nuts, bolts, washers, etc. need to be replaced when changing the diff?

technically, the crimped nuts for the prop coupling should be replaced but if they're still nice and tight, i woudn't bother. maybe a dab of loctite if you have any handy

Tue Jul 17, 2007 9:40 pm

gareth wrote:
FlashBastd wrote:Do any nuts, bolts, washers, etc. need to be replaced when changing the diff?
technically, the crimped nuts for the prop coupling should be replaced but if they're still nice and tight,

= ideal world!

i woudn't bother. maybe a dab of loctite if you have any handy

= real world

Tue Jul 17, 2007 9:48 pm

Lol, thanks Brian!

Tue Jul 17, 2007 10:05 pm

i actually did replace mine last time i was there but they were fairly loose and i was over at the bmw dealer anyway. they're only about 12p each so it's not going to break the bank!

i have had several guibo couupling bolts break due to incorrect fitting and subsequent loosening so i thought it best to do the whole lot when adding a heap more M30 torquey goodness! even the prop bolts are less than a quid so no worries there too. it's the fuel to take me 25 miles to the dealer that is offputting

Wed Jul 18, 2007 3:05 am

I replaced all the nuts and bolts but also had to have the replacement diff tapped due to rust!!

Wed Jul 18, 2007 12:46 pm

and ignore the haynes manual (obviously)as it omits to mention the 2 bolts on the very top of the diff (Haynes manual comes in handy to put between your jack and the diff tho) Just got my open diff off and as soon as i have eaten its on with the slipper!

all the bolts are 19mm by the way, the ones to the prop are 17mm

Wed Jul 18, 2007 6:53 pm

karaokebykris wrote:(Haynes manual comes in handy to put between your jack and the diff tho)

............. should you wish to totally overload your subrame mounting bushes unnecessarily