Rear diff rebuild and upgrade

I

InterlagosMC

Member
Hi all, looking for recommendations for someone to rebuild my lsd and upgrade is to 4.1 ratio, I already have the new crown gear and pinion and have seen mention of heasman diffs but wondered if there’s any others to consider.

Thanks
Andy
 
I was looking into this recently too, the other place I have seen mentioned is https://www.jcracing.info/product/18/ratios-type-210-215-230
 
They are all far from me :D

I was thinking of shipping my diff on a pallet, but may end up DIYing it
 
Heasman if you want to save yourself money doing some of the legwork yourself, Everything M3's if you want an easy in and out service and are happy to pay for the luxury. Can't go wrong with either.

ed80 said:
I was thinking of shipping my diff on a pallet, but may end up DIYing it
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Got my local garage to whip the diff off, chucked it in the boot and drove it up to Dave myself. Bit of a mission, Bristol's probably about same distance as it was for me, road trip! Was certainly a bit of a drag doing the trip again to pick it up but worth the money it saved.

If your in Bristol, Redish has to be a good shout but won't be cheap.
 
I looked at diy as I’ve done everything else myself on the car but when I looked at the tooling I’d need to buy and setting the backlash up correctly I just thought it works out the same to get a professional to set it up right and have it rebuilt at the same time.

On another note when I spoke to Dave @ heasman he said about an upgrade to the e36 evo diff internal as it changes the diff from viscous style to plate lsd
 
AndyBeech said:
If your in Bristol, Redish has to be a good shout but won't be cheap.
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Redish will certainly do it, but they charge £1400 for the CWP on its own, and don't fit customer supplied parts. I got the last cheap CWP from Douglas Park on eBay for about half that :D

I'll give Heasman a call and see what they quote. The problem for me is I am a contract worker, so a day off to take the diff to Heasman is pretty expensive in itself.
 
ed80 said:
AndyBeech said:
If your in Bristol, Redish has to be a good shout but won't be cheap.
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Redish will certainly do it, but they charge £1400 for the CWP on its own, and don't fit customer supplied parts. I got the last cheap CWP from Douglas Park on eBay for about half that :D

I'll give Heasman a call and see what they quote. The problem for me is I am a contract worker, so a day off to take the diff to Heasman is pretty expensive in itself.
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Ah yeah that sounds about right, I do love James but damn his prices sometimes are :o

Good luck with it whatever you choose, Heasman did my diff and 4.1 and I've had no issues since including a few track days with it. Not that I expected any issues of course.
 
Got a price back from Dave at Heasman that seems very reasonable. I am still leaning towards DIY because I have most of the tools already, but it's good to know there is an affordable alternative if I get cold feet.
 
Worth speaking to redish I can't promise bit they might be able to fit the part if it's in the sealed original packaging...

Alternatively everything M cars in Banbury did mine but that was supply and fit...
 
It lowers the gearing so you get more response in every gear, but will also get to the redline at a lower speed in each gear.

I suspect it might be more useful on a track focused car like Eds by reducing the gaps between the gears, but not so much on the roads unless you are on a bit of a mission!
 
Mr Tidy said:
It lowers the gearing so you get more response in every gear, but will also get to the redline at a lower speed in each gear.
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This! It makes most of the gears more usable, you get to shift from 2nd into 3rd at the redline without breaking the speed limit :thumbsup:

The only downside is that cruising RPMs are higher, but my long term plan is to fit a DCT box, which works with the 4.1. It gives a new 7th gear slightly longer than the standard 6th for motorway use, and six other nice close ratios to paddle shift through.
 
What wheel size are you running? 4.1 is perfect for 19". Prob a bit much, depending on the track for 18's with low profiles. Obviously youve looked at the other ratios? 3.91 is a great match for 18s.
 
Vanne said:
What wheel size are you running? 4.1 is perfect for 19". Prob a bit much, depending on the track for 18's with low profiles. Obviously youve looked at the other ratios?
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I will be running 18s with standard profile tyres, so same as 19s. I'm going for fast road, rather than track focus. I have a big spreadsheet comparing speed in gear with different gearboxes and final drive ratios, 4.1 seems the best fit with the M4 DCT box.
 
Vanne said:
Ahh oh Kay, that clears things up a bit. How’s the gearbox mating coming along? :thumbsup:
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It should be pretty trivial, there are adapter plates and gearbox mounts so it all just bolts up. The only machining needed is to shorten the driveshaft a touch. I am swapping out the stock ECU for a MaxxECU which will control the engine and gearbox together, the aftermarket transmission control units don't really work in the Z4M because the stock ECU doesn't support an automatic.

Step one is the 4.1 diff and the MaxxECU install. Once these are done I will move on to the gearbox.
 
ed80 said:
Vanne said:
What wheel size are you running? 4.1 is perfect for 19". Prob a bit much, depending on the track for 18's with low profiles. Obviously youve looked at the other ratios?
Click to expand...

I will be running 18s with standard profile tyres, so same as 19s. I'm going for fast road, rather than track focus. I have a big spreadsheet comparing speed in gear with different gearboxes and final drive ratios, 4.1 seems the best fit with the M4 DCT box.
Click to expand...
Would you be able to post the in-gear speeds with the standard gearbox and different final drive ratios please? PM if you prefer. Cheers
 
BMWZ4MC said:
Would you be able to post the in-gear speeds with the standard gearbox and different final drive ratios please? PM if you prefer. Cheers
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Sure, I calculated it as the RPM at 60mph in each gear, but you should be able to modify this for whatever speeds you want:

6MT (3.67)
1st: 12267
2nd: 7050
3rd: 4681
4th: 3469
5th: 2820
6th: 2397

6MT (4.1)
1st: 13894
2nd: 7985
3rd: 5302
4th: 3929
5th: 3194
6th: 2715

So with the 4.1 your change from 2nd to 3rd happens almost exactly at 60mph
 
From the Redish website - expressed as MPH speed at 8,000 rpm.

3.62 ratio
1st 40
2nd 68
3rd 102
4th 139
5th 171
6th 206

4.10 ratio
1st 36
2nd 60
3rd 90
4th 123
5th 151
6th 182
 
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