Differential Upgrades

bradz · Post by **bradz** » Wed Jan 02, 2019 11:29 pm

Mikey_Boy wrote: ↑Wed Jan 02, 2019 1:18 pm Happy New Year everyone! I've just spoken with my local Indy and they are suggesting getting a standard diff rebuilt to standard spec is going to be tricky due to lack of parts availability. Not sure how true that is so any advice on that is much appreciated!

Just looking at the above, the gripper diffs are also a tempting option - is there a ballpark price for the build?? I'd probably keep the 3.64 ratio and something not too aggressive as the car is mainly used on the road.

It seems to me to be much easier to just swap the whole unit than have to go through the pain of taking the diff out and then have the car hanging about for weeks whilst the diff is sorted...

As ever, any advice is much appreciated!

Sack your Indy, Rebuild parts are available from BMW even ebay! I bet they don't have the tooling/ Expertise.

Speak to Neil @ https://www.automac.co.uk/

Tell him Adam sent you

Mikey_Boy · Post by **Mikey_Boy** » Fri Jan 11, 2019 3:17 pm

Ok - I'm in - just awaiting payment details from Neil for an 8 plate gripper diff on a standard 3.64 ratio....

TomK · Post by **TomK** » Fri Jan 11, 2019 7:30 pm

Be really interested to hear your thoughts on it once you've run it in. Keep us updated please.

bradz · Post by **bradz** » Sat Jan 12, 2019 7:00 pm

Hopefully pickup my diff built by Neil next week. Excited like a kid at Christmas

Mikey_Boy · Post by **Mikey_Boy** » Fri Feb 01, 2019 11:04 am

I'm not far behind you Bradz... Mine's due in a couple of weeks!

I'm thinking I should replace the diff mounting bushes as well - anyone used powerflex or should I stay OEM? Items 20 and 21 on this link:

https://www.powerflex.co.uk/products/Z4 ... 169/1.html

Any help or thoughts always appreciated!

bradz · Post by **bradz** » Sat Feb 02, 2019 4:24 pm

I went with powerflex diff bushes on the Z4M, I noticed no negative effects.

I went with them on the M3 and you can hear the diff whine through the car... Very odd how they affect the M3 more!

Gripper and 4.10 fitted to the M3 yesterday! Unfortunately I cant try it out yet as we are waiting for a new centre bearing from BMW.

Mikey_Boy · Post by **Mikey_Boy** » Sat Feb 23, 2019 10:33 pm

Bradz - how are you getting on with your diff?

Mine (8 plate gripper with 3.64 final drive) has been fitted recently and I've done about 200 miles on it so far - nothing too heavy other than a few test corners. It's a fruity little number and mine does make quite a bit of noise at low speed - I've noticed some extra noise at motorway speed as well but I think that's down to the mounting bushes as I've gone for powerflex.

Any updates appreciated!

bradz · Post by **bradz** » Sun Feb 24, 2019 8:43 pm

Its bloody loud!

I went with the 12 plate and 4.10... At low speed turns the car sounds horrific as you can hear the clutch binding - I was warned.

I too went with power flex bushes... I fitted them to the diff in the Z4MC and noticed no difference at all, fitted them to the gripper in the m3 and you can hear it resonate through the whole car! - going back to stock bushes.

Initial impressions on the road are... Its noisy, But the first time it locked and spat me out of a corner faster than I deemed possible I knew I made the right decision!

Booked a track-day on the 4th March at Bedford Autodrome - to really test it out! I'll keep you posted!

Adam

Mikey_Boy · Post by **Mikey_Boy** » Mon Feb 25, 2019 11:01 am

Thanks Bradz...!

Glad it's not just me that thinks it's aggressive...

Just to add to the points I made above - agree with Bradz - at low speed (anything below 30mph) it makes quite a lot of cracking noises - with the 8 plate I'm told this improves with miles so a good excuse to drive the car more to see how that works out. I've had aggressive diffs in other cars so this is familiar but quite a surprise the first time you hear it!!

At higher speed, the car feels super locked down with no clutch binding noises at all from the diff - and especially under braking the car feels much better.

In a straight line at motorway speeds, there is a slight whine from the diff and it does resonate a little at certain - like Bradz, I'm looking to go back to OEM mounting bushes to try and resolve that as I believe that's a mounting issue.

I'm also looking for a UK trackday to try the diff out in anger - on the couple of roundabouts I've tried it on, it is very impressive...

More to come!

Mikey_Boy · Post by **Mikey_Boy** » Wed Apr 03, 2019 12:00 pm

Hi folks,

Another quick update - the diff is getting better and better with miles - driving on A & B roads is doing the trick to run it in. It is still laugh out loud noisy pulling away from junctions, but at speed now it is much quieter.

I have changed the front bush back to OEM - that has taken away the whining at speed so a result there as well...

Hopefully I'll be on track with it at the end of April to try it out in anger!

bradz · Post by **bradz** » Thu Apr 04, 2019 10:05 pm

It's funny you should say that...

Mine has solid subframe mounts and powerflex bushes fitted to the diff.

Yesterday I ordered a bmw front Bush and a new rear plate, and superpro subframe bushes.

At 75mph it was 86db in the car... I know its a track car but that's way too much for me!

On a positive note really like the way it puts the power down coming out of a corner.

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