Diff rebuild - removing pinion

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fcp
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Rebuilding a set of axles and I'm as far as removing the pinion which I had expected to push out on the press. The MB workshop manual has a special tool specified though (601 589 02 63 00)  and that makes me nervous - you'd expect them to just suggest using a press if that was a safe way to do it.

Anyone here done this?any other advice on the rebuild (esp around setting backlash/ preload)? 

G-Restorations
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Re: Diff rebuild - removing pinion

I just whack them out with a hide hammer,  what ratios are you using Ben?

Gordon O

fcp
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Re: Diff rebuild - removing pinion

G-Restorations wrote:

I just whack them out with a hide hammer,  what ratios are you using Ben?

Gordon O

Hi Gordon,

I was tempted to do just that, but having never worked on them before I thought better of it (rash decisions tend to get me into expensive trouble I have learned :D) and decided to see what others did. I'll put them in the press tomorrow I think.

The ratios are 35:8s (high torque, high RPM 606 on 35s or 37"s).

When you have  reassembled them, what have you done about shimming and preload (all new bearings and seals are going in so I imagine things will change)?

The correct MB tools are expensive for a job I will do at most a couple of times; I wonder whether this might be a case where taking it to someone to reassemble might be better value (these guys have OK reviews http://www.hardyengineering.co.uk/differential-repairs-in-surrey-london/)

Cheers, Ben

G-Restorations
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Re: Diff rebuild - removing pinion

Ben, the pinion should come out easily, it's only being held by the fit of the nose bearing on the shaft.  

There is a thick shim under the inner pinion outer race this adjusts the position in and out of the pinion into the diff. I didn't touch this.

The diff itself is adjusted by the same thick shims on either side of the bearings, these shims come in a range of thicknesses so you can alter the position of the diff left and right  and by increasing the total thickness of the shims you can increase the preload. 

The preload on the pinion is adjusted by the tightness of the nut which compresses the collapsable ring in between the bearing, I just did mine by "feel"   it all seems to be OK  I had a trip down to Axels in Bristol this weekend and I've no whiney diffs.

I've created a spreadsheet to calculate revs/gearing/roadspeed  it's available here  http://www.pxwheels.com/gearingcalc.xls

I think 4.3:1 diffs and 35" tyres are a big mistake for comp offroading,  you'll really be limiting the number of gears you can use, and you'll be putting high loads on the rest of the transmission,  I think 5.3:1  or even lower would be more use.  what type of competion are you doing?

Gordon O

fcp
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Re: Diff rebuild - removing pinion

G-Restorations wrote:

Ben, the pinion should come out easily, it's only being held by the fit of the nose bearing on the shaft.  

There is a thick shim under the inner pinion outer race this adjusts the position in and out of the pinion into the diff. I didn't touch this.

The diff itself is adjusted by the same thick shims on either side of the bearings, these shims come in a range of thicknesses so you can alter the position of the diff left and right  and by increasing the total thickness of the shims you can increase the preload. 

The preload on the pinion is adjusted by the tightness of the nut which compresses the collapsable ring in between the bearing, I just did mine by "feel"   it all seems to be OK  I had a trip down to Axels in Bristol this weekend and I've no whiney diffs.

I've created a spreadsheet to calculate revs/gearing/roadspeed  it's available here  http://www.pxwheels.com/gearingcalc.xls

I think 4.3:1 diffs and 35" tyres are a big mistake for comp offroading,  you'll really be limiting the number of gears you can use, and you'll be putting high loads on the rest of the transmission,  I think 5.3:1  or even lower would be more use.  what type of competion are you doing?

Gordon O

Someone else who is a night owl!

OK, that's helpful to know. Everything in the diff except the pinion and gear is being replaced (seals, bearings etc), so a new crush washer will be required and my feeling is that both the pinion and LR diff will need to be re-shimmed.

Use is exclusively rally raid -so primarily high speed, high gear, high rpm, loose surface (rather than that mud-plugging with lots of high-torque, heavy right foot in a low gear! ). I'd guess we'll be spending most of our time between 60 and 90 MPH

The transmission is a GS6-53DZ (BMW M series), which I did some calculations on, based on the  ratios: 

5.08, 2.8, 1.78,1.26,1,0.84  with 1.05 (high on VG150) and 4.3 diff and 35" tires

Road speed at given RPM in miles per hour
Gear 1500 RPM 3750 RPM 6000 RPM
1 7 17 27
2 12 31 49
3 19 49 78
4 27 69 110
5 35 87 138
6 41 103 165