CAN YOU SHORTEN PROPSHAFTS? My LSD won't fit!!!!!!!!

Post Sat Oct 22, 2005 12:02 am

I have just tried replacing my 3.46 diff with a 3.91 LSD. However when I removed the 3.46 it dropped while attached to the propshaft. I thought nothing of it until when I tried to fit the 3.91 the holes wont quite line up. I have tried rachet straps but nothing seems to work.

I guess that when the old diff dropped it must have extended the shaft. I have heard it is possible to alter the length of the shaft. Am I right?

Please help me as I am stuck with an undriveable car

Many thanks in advance

Post Sat Oct 22, 2005 2:07 am

undo the center bracket that hold's the prop up, and whack the diff end with a hammer (without the diff on ofcourse) and if it has come out it will go back down,

before you do that tho, have a look at the center join and see i it has acctually moved a bit, there should be some sort of muck/oil mark on it

hth

Post Sat Oct 22, 2005 10:57 am

craigieeb wrote:undo the center bracket that hold's the prop up, and whack the diff end with a hammer (without the diff on ofcourse) and if it has come out it will go back down,

before you do that tho, have a look at the center join and see i it has acctually moved a bit, there should be some sort of muck/oil mark on it

hth

I wouldn't whack the end of the prop with anything, unless you like changing gearboxes for a hobby.
Take off the heatshield which covers the diff centre bearing.
Slacken the sleeve nut around the splined section, so that the prop can lengthen and shorten. Don't seperate the two halves unless you have marked it so that the same splines go back together.
Slacken the two bolts holding the centre bearing.
Fit your diff, and reconnect the prop at the diff end.
Lightly tighten the bolts holding the centre bearing.
Mark the position of the centre bearing bracket on the car body with a pencil.
Slacken the bolts, move the bracket forwards about 3mm, and tighten the bolts with the bracket in this position.
Tighten the sleeve nut on the prop.

Post Sat Oct 22, 2005 11:53 am

Why do you have to move it 3mm?

Andrew

Post Sat Oct 22, 2005 12:35 pm

Brian - you're such a legend fella!

Post Sat Oct 22, 2005 2:24 pm

Demlotcrew wrote:Why do you have to move it 3mm?

Andrew

Preloads the centre bearing. Don't know the consequences of not doing it, but that's what your supposed to do.

Post Sat Oct 22, 2005 2:26 pm

Brianmoooore wrote:
Demlotcrew wrote:Why do you have to move it 3mm?

Andrew
Preloads the centre bearing. Don't know the consequences of not doing it, but that's what your supposed to do.

Dude im not doubting you, its not the first time ive heard this (TIS) and i have always done it, just wondering why. (For a M3 i think you need to pull it back instead)

Andrew

Post Sat Oct 22, 2005 3:54 pm

Thanks Brianmoooore.

Is there any chance people could show me pictures? I know I'm askin a lot but I do struggle sometimes.

Also should the prop be moved 3mm forward as in towards the engine?

Cheers

Post Sat Oct 22, 2005 4:13 pm

Project_E30 wrote:I have just tried replacing my 3.46 diff with a 3.91 LSD. However when I removed the 3.46 it dropped while attached to the propshaft. I thought nothing of it until when I tried to fit the 3.91 the holes wont quite line up. I have tried rachet straps but nothing seems to work.

I guess that when the old diff dropped it must have extended the shaft. I have heard it is possible to alter the length of the shaft. Am I right?

Please help me as I am stuck with an undriveable car

Many thanks in advance

Post Sat Oct 22, 2005 4:19 pm

Project_E30 wrote:I have just tried replacing my 3.46 diff with a 3.91 LSD. However when I removed the 3.46 it dropped while attached to the propshaft. I thought nothing of it until when I tried to fit the 3.91 the holes wont quite line up. I have tried rachet straps but nothing seems to work.

I guess that when the old diff dropped it must have extended the shaft. I have heard it is possible to alter the length of the shaft. Am I right?

Please help me as I am stuck with an undriveable car

Many thanks in advance

yes you can you can shortern propshafts, they is a half nut were the 2 prop pieces are joined,you can adjust by screwing it clockwise if you want to shorten it.

Post Sat Oct 22, 2005 6:55 pm

Project_E30 wrote: Is there any chance people could show me pictures? I know I'm askin a lot but I do struggle sometimes.

As if by magic. Heres the sleeve nut.....

As for pulling the centre bearing back on an M3, it may have something to do with the prop being reversed compared to a non-M3 prop. By that I mean on the M3 prop, the UJ is between the centre bearing and diff, where as on the non-M3 prop the UJ is between centre bearing and gearbox. See the piccy below.
The bottom prop is my M3 prop and the top one is off my 325i...

Post Sat Oct 22, 2005 10:02 pm

Is that a label from Moseley Motors on that prop ? Looks just like Nigels writing.....!!!

Post Sun Oct 23, 2005 12:54 pm

JMC330i: Many thanks your a star!

Two final questions then:

Should the prop be moved 3mm forward as in towards the engine?

Where abouts under the car is this as there are two or more heatshields. again is a pic asking too much?

Cheers

Post Sun Oct 23, 2005 1:44 pm

Two final questions then:

Should the prop be moved 3mm forward as in towards the engine? Yes
Where abouts under the car is this as there are two or more heatshields. again is a pic asking too much? Prop centre bearing is a clue. Right in the middle of the prop.

Post Sun Oct 23, 2005 5:08 pm

kam-325i wrote:Is that a label from Moseley Motors on that prop ? Looks just like Nigels writing.....!!!

Yup, they were the only place who had an E30 M3 prop when I was looking. Very helpful bloke that Nigel