edit: Renamed thread....

How do you determine which shim to use when changing the final drive?

The kit I've got from which is a motorklasse 4.44 came with a selection of three shims (3.29mm, 3.23mm, 3.35mm), and the OEM one from the diff looks to be thinner than all of these.

I don't have any info with the kit as to what shim to use specifically, and what the backlash should be.

 

(It's the Scienc of speed kit by the way)

 

There is no specific shim. Tooth contact should be checked with gear teeth paint, by someone who is VERY savoy at diff building.

What you can do is get a reccomendation from someone on the board which shims they used in their 4.44 kit, and start there.

You may still need to disassemble the dif and re-shim it.

**Here's the best advice any S2000 dif builder will get: (mere mortals will not be able to follow this)
-The press fit of the pinion bearing on top of the shim is enormous. you may very likely ruin the bearing, or consume lots of time, if you need to keep re-shimming.
-Take the original bearing (must be in good condition) and grind/polish out the middle of the bearing until it slides on with no press-fit.
-Build the dif with no pinion seal installed, using a spacer to replace the drive flange.
-paint the teeth, make your call on tooth contact.
-Now, you can swap the shim and put the diff back together in 5 minutes.
-Once the pattern is correct, press on your new bearing for final assemble.

NOTE! this is why many diff builds whine, or fail. Because the time it takes to re-shim. No one wants to buid a diff twice, or 3-4 times, they would rather just call it close enough.

 

That's excellent advice Billman, much appreciated. You're exactly right, the time consuming re-shimming is the pain in the arse bit.

I'll relay that to the garage doing the work. I've got the original bearing to put to use...

It would be handy to find out what shim other folk have used as a kind of starting point.

 

Don't forget the backlash also changes the tooth contact a bit.
So get the backlash to spec before looking at the contact patch.
When you set the backlash, use a setting that you could use in the final build: make sure the locking plates line up with the "castle" nut.
Those locking plates can make it impossible to find the perfect backlash.

 

Well, I removed my pinion bearing about 7 times to reshim and the bearing never got damaged. "set-up" bearings are nice, but not absolutely necessary. Then again I have access to a bearing splitter and a local DIY shop that lets me use their press for a few bucks/hour. Good luck!

Edit: typo.

 

Cheers for all the extra info folks. On some of the example installs I've been looking at, it shows a contact pattern, and a 'coast' contact pattern. Any idea's how the two different one's are produced. I imagine with one you turn the diff one way, and the other you turn it back and fouth to make the contact pattern, is that right?

Also, I'm not sure tipex gives the clearest indicator really, whats the best type of paint to use?

Although the garage is doing the re-install, I just want to be armed with as much info as possible to avoid needing it re-done.

 

Put some friction load (stop it from turing with your hand) on the ring and turn the pinion CW and CCW.
That will give you a "drive" and a "coast" contact pattern.

IIRC, looking at the front of the diff with the drain pointing downwards.. you turn the pinion CW for the "drive" contact.
(but it could be the other way around... )
When the drive contact is ok the coast should be ok too.
Drive = most important.

The manual suggests Prussian Blue "Ink", used in workshops.
I've used white detector paint used for material defect finding.
Its a bit chalky.. if you know what I mean.

 

I'm having a real nightmare with this diff. It's gone back to the current garage 3 times now. I've seen the contact pattern in blue dye, which looks centered on the teeth on the drive side and the coast. It's got new bearings in with this kit, and fresh oil obviously. Backlash within OEM tolerance the garage says (0.7 mm I think he said perhaps? If that sounds right...)

No whine on coast. As soon as you get lightly on the throttle it rings/whines. Pitch of the noise is directly related to speed. A bit more throttle and it whines less. Alot of throttle/lowish gear and I'd not be able to hear if it whines. Above 100mph and guess the pitch of the noise is too high for me to hear it anymore. I'd say the amount of noise is the same at any speed, it's really light throttle that makes it loudest, and speed that changes it's pitch.

The supplier of the part said, it's an OEM derived part so should be silent. They said it sounded like a fitment problem, a pre-load issue, so this time it's gone back and got (another) new crush sleeve.

I thought it was a bit better at first, but after the run home, it's still bad, the charecteristics of the problem are just subtly different. Some times the whine warbles a bit like it's pulsing. I notice a slight gear rubbing noise when pulling to a stop in neutral now.


I don't know what to do with it now, coming to wits end with this problem. If anyone has any thoughts on what the issue is based on the charecteristics above, i'd appreciate it.

Does anyone know what the torque needs to be on the pinion nut? This controls pre-load I think? I could get this checked by a local garage.

Other than that, I'm out of idea's. I can wait until an 04+ OEM diff turns up on ebay, and put it back to stock, but that would be an epic loss of time and money and very disapointing.

 

Nominal OEM backlash (BL) should be between 0,09-0,11mm.
Minimal BL should be 0,05mm.
Max difference between 4 measurements should be no more than 0,07mm.
Recommended BL for my 4.57 set was 0,26mm.

So... 0,70mm is way out of spec, IF it is really set at that BL.
(Lets hope "they" didn't primarily use BL to get the contact pattern right)

Changing the BL that much (moving ring gear sideways) will change the contact pattern, so another shim is needed to get that right.