Stripping a diff

[SAE30]

Anyone know how to swop out internals on a diff???

[ShakeyC]

What parts of the diff are you trying to swap? And what diffs are they?

[SAE30]

I wanna swap the crown wheel and pinion, im gonna take the crown wheel and pinion from a e36 diff and put them into my e30 LS diff, please help

[ian332isport]

I'm afraid it's not really a DIY job, unless you know exactly how to set it up again.

It's easy enough to physically swap the parts, but setting the pinion pre-load, and getting the correct gear mesh is best left to someone with the tools and knowledge to do it properly.

Ian.

[SAE30]

I'm afraid it's not really a DIY job, unless you know exactly how to set it up again.

It's easy enough to physically swap the parts, but setting the pinion pre-load, and getting the correct gear mesh is best left to someone with the tools and knowledge to do it properly.

Ian.

Thanks Ian.
after doing my homework, im NOT even going to attemp to do this, i've ask this before but just want to make sure sure....
will the ratios(crown wheel and pinion) from the e36 325i diff fit into my e30 ls diff casing?

[GeoffBob]

i've ask this before but just want to make sure sure....
will the ratios(crown wheel and pinion) from the e36 325i diff fit into my e30 ls diff casing?

Yes. Find a good quality diff and gearbox rebuilder in your area and have them do the swap for you. If in doubt, ask beforehand that they know how to set the correct pre-load. If they can't, then they shouldn't be rebuilding differentials, and then take it somewhere else.

[SAE30]

tHANKS

[GeoffBob]

Also, while they are at it, get them to check the operation of the LS unit at the centre of the diff. If it's an old, well used LSD, the chances are good that it will require a new set of clutch discs. In which case, make sure they know how to reassemble the LS properly, set up the shims, measure/adjust the percentage slip etc.

[UweM3]

Also, while they are at it, get them to check the operation of the LS unit at the centre of the diff. If it's an old, well used LSD, the chances are good that it will require a new set of clutch discs. In which case, make sure they know how to reassemble the LS properly, set up the shims, measure/adjust the percentage slip etc.

I have a ratio change lined up as well but won't even bother with the old clutches. Given the average age of a used diff and not knowing what mileage I just want everything new. I have to pay for the labour anyway, so why not do it right first time.

[GeoffBob]

Also, while they are at it, get them to check the operation of the LS unit at the centre of the diff. If it's an old, well used LSD, the chances are good that it will require a new set of clutch discs. In which case, make sure they know how to reassemble the LS properly, set up the shims, measure/adjust the percentage slip etc.

I have a ratio change lined up as well but won't even bother with the old clutches. Given the average age of a used diff and not knowing what mileage I just want everything new. I have to pay for the labour anyway, so why not do it right first time.

I fully agree.

[SAE30]

Also, while they are at it, get them to check the operation of the LS unit at the centre of the diff. If it's an old, well used LSD, the chances are good that it will require a new set of clutch discs. In which case, make sure they know how to reassemble the LS properly, set up the shims, measure/adjust the percentage slip etc.

I have a ratio change lined up as well but won't even bother with the old clutches. Given the average age of a used diff and not knowing what mileage I just want everything new. I have to pay for the labour anyway, so why not do it right first time.

I fully agree.

okay so they inspected the internals of my diff, checking the ls, the guy told me that it had a bit of play? does this mean worn clutches?

[GeoffBob]

okay so they inspected the internals of my diff, checking the ls, the guy told me that it had a bit of play? does this mean worn clutches?

Play on what? If he's referring to backlash on the planet and sun gears this has nothing to do with the LS clutches, and you might be able to get away with it. Depends how badly the teeth are worn down. If you're through the hard surface, you can forget it.

Unless there is blatantly obvious slippage on the clutches (IE the LS doesn't work) the slip has to be measured. Try get a specific diagnoses from him with regard to the clutch mechanism. If he can't answer you he probably doesn't have the right tools for the job, so take it somewhere else. "A bit of play", unfortunately, says very little.

[SAE30]

okay so they inspected the internals of my diff, checking the ls, the guy told me that it had a bit of play? does this mean worn clutches?

Play on what? If he's referring to backlash on the planet and sun gears this has nothing to do with the LS clutches, and you might be able to get away with it. Depends how badly the teeth are worn down. If you're through the hard surface, you can forget it.

Unless there is blatantly obvious slippage on the clutches (IE the LS doesn't work) the slip has to be measured. Try get a specific diagnoses from him with regard to the clutch mechanism. If he can't answer you he probably doesn't have the right tools for the job, so take it somewhere else. "A bit of play", unfortunately, says very little.

okay i will check with him,

i have 2 options on the ratios, either 2.93 or 3.15, which do u guys think is better, remember i have the 3.2 with the zf 5 speed m3 tranny..... i love driving fast but not really a drag racer as such....please advise

[GeoffBob]

With the ZF typeC 5-speed and the 3.15 diff and a set of 215/40/16 rear tyres, at 6500RPM your vehicle speed will be:

54 km/h in 1st gear,
90 km/h in 2nd gear,
136 km/h in 3rd gear,
181 km/h in 4th gear, and
225 km/h in 5th gear.

These figures serve to provide you with an indication of your top speeds in each gear. I know that you don't plan to drive around at 6500RPM.

Also, at 120km/h in 5th gear your revs will be at 3475RPM, and at 140km/h, also in 5th, your revs will be at 4050RPM.

However, with the 2.93 diff, at 6500RPM your vehicle speed will be:

58 km/h in 1st gear,
97 km/h in 2nd gear,
146 km/h in 3rd gear,
195 km/h in 4th gear, and
242 km/h in 5th gear.

At 120km/h in 5th gear your revs will be at 3225RPM, and at 140km/h, also in 5th, your revs will be at 3750RPM.

If you plan on doing a lot of Motorway driving, go for the 2.93 ratio. This will give you lower (quieter) RPM and better economy. Given the torque of your 3.2 S50 engine I don't think you need worry about the slight gain in acceleration of a 3.15 over a 2.93 diff. At least not unless you are planning to drag race and you have wide enough rubber 'round your rims to effectively lay that torque down in 1st and 2nd gear! The 3.15 diff will give you a slight improvement in acceleration over the 2.93 diff, but at the expense of top speed.

EDIT: Values have been updated to reflect tyre size shown below.

[SAE30]

With the ZF typeC 5-speed and the 3.15 diff and a set of 205/50/16 rear tyres, at 6500RPM your vehicle speed will be:

57 km/h in 1st gear,
96 km/h in 2nd gear,
143 km/h in 3rd gear,
192 km/h in 4th gear, and
238 km/h in 5th gear.

These figures serve to provide you with an indication of your top speeds in each gear. I know that you don't plan to drive around at 6500RPM.

Also, at 120km/h in 5th gear your revs will be at 3275RPM, and at 140km/h, also in 5th, your revs will be at 3825RPM.

However, with the 2.93 diff, at 6500RPM your vehicle speed will be:

61 km/h in 1st gear,
103 km/h in 2nd gear,
154 km/h in 3rd gear,
206 km/h in 4th gear, and
256 km/h in 5th gear.

At 120km/h in 5th gear your revs will be at 3050RPM, and at 140km/h, also in 5th, your revs will be at 3550RPM.

If you plan on doing a lot of Motorway driving, go for the 2.93 ratio. This will give you lower (quieter) RPM and better economy. Given the torque of your 3.2 S50 engine I don't think you need worry about the slight gain in acceleration of a 3.15 over a 2.93 diff. At least not unless you are planning to drag race and you have wide enough rubber 'round your rims to effectively lay that torque down in 1st and 2nd gear! The 3.15 diff will give you a slight improvement in acceleration over the 2.93 diff, but at the expense of top speed.

The presented figures will differ marginally for other tyres. Let me know what rubber you plan to use and I will make corrections.

thanks GeoffBob, this is to the tee........ im using 215/40/16 at the rear

[GeoffBob]

SAE30, I've updated my previous post to reflect your tyre size. The slightly smaller rolling circumference of your smaller radius tyres (due to the 40 profile) will bring your revs up slightly at a given road speed. The other way of looking at it is that your road speed will be lower at a given RPM value.

I'd definitely go for the 2.93 ratio diff. It will make a stunning difference compared to what you had on the car before.

[SAE30]

SAE30, I've updated my previous post to reflect your tyre size. The slightly smaller rolling circumference of your smaller radius tyres (due to the 40 profile) will bring your revs up slightly at a given road speed. The other way of looking at it is that your road speed will be lower at a given RPM value.

I'd definitely go for the 2.93 ratio diff. It will make a stunning difference compared to what you had on the car before.

i think im gonna go with the 2.93...

thanks

[RoadHazard]

I'm falling into the same situation where E30 M3 diffs are hard to find around here (Thailand). Right now I'm in the process of searching for the ones that work out right. I really don't want to work on the diff internals if I don't have to.