E9X M3 diff flange bolts counterbalances!?!

[DR-JEKL]

Hey guys

I have a 335i and have recently installed a complete driveline from a M3 into my car. This retrofit conversion has been commonplace for years now and the workshop who performed this conversion for me had done at least 4 of them in the past.

It largely all bolts up but to mate the diff up a custom driveshaft had to be manufactured as my 335i shaft wouldn't fit the M3 Diff flange. I purchased a E38 driveshaft (the 540i and 740i share the same type of diff flange to the M3) and the rear portion of my 335i was cut and the 740i section was welded to the shaft and balanced by a driveline specialist.

Upon driving the car above 80 km/h I was experiencing a humming vibration through the car (Seats, steering wheel etc) and it didn't dissapear at 140 km/h or when i applied the throttle or backed off the throttle.. It sounded like it was an out of balance driveshaft...

I was initially perturbed that a driveshaft would be cut n shut and welded as this sounded like a crude method, but alas there have been many conversions conducted on 135/335i around the world and this is the method they used...

Now to get to the reason for creating this thread and how it may be of relevance to you E9X M3 owners!

Discussing this issue with a fellow enthusiast who is a tech head and dabbles in a lot of coding, tweaking, research he came across some info in the BMW ISTA that may be the reason for my driveline vibration..

Apparently the driveline is setup to quite fine tolerances and each diff is balanced after assembly (you'll see a little round recess drilled in the flange - this is the method of correction where material is removed from the point of imbalance to ensure its precisely balanced)

drilling of the flange to remove imbalance:



In addition to the machining of the diff flange for balancing correction, there is counterbalancing on the bolts where the driveshaft connects to the diff flange as required for fine corrections (i.e if they cant get the diff perfectly balanced at the factory the technician marks the diff as OK or requiring addition counterbalancing - this is determined by the coloured mark on the diff)







Example of marks:



prior to 09/09 the counterbalancing was done with the use of washers on the marked hole )as indicated by the colour mark by the bmw factory tech) or after 09/09 special bolts once again as indicated by the colour marks. The diff I had was from a 2011 build M3 so if it required counterbalacing, it would require bolts.



bmw part #26112284154 black
bmw part #26112284153 green
black bolt is for blue marking
green is for yellow marking
if diff has white marking no counterbalance bolts required

My local BMW dealer (I'm in Australia) got me some prices for these bolts, he had some trouble as they weren't in the system as it seems no-one has ever ordered them and he discussed it with the workshop foreman who said they weren't aware of these counterbalance bolts..

They're a special order from Germany, and since I have no markings visible on my diff I would have to order both and attempt to find the orientation they should be mounted by installing driving the car and checking and removing and changing the position etc (not an easy task to do...)





*Quoted prices in AUD not USD*

I'm hoping the car doesn't need these bolts, as my diff has no marks so it will be a long process in attempting to locate the correct position on the flange which requires the counterbalance bolt.

My local BMW workshop foreman stated that they treat the diff flange bolts as a once use item (even though BMW procedures don't stipulate that the need to be replaced) and was unaware of the counterbalance bolts or washers...

Have any of you M3 owners ever been aware of the counterbalance bolts or washers?!?!

[Dackelone]

Perhaps its something more simple/common like a bad center driveshaft (support)bearing that bad?

#8 in your parts diagram.

Have you tried putting your car up on a lift and driving it up past 80 kph and have a tech or two under the car to look to see whats moving/vibrating. They could use a mechanic's stethoscope to probe the driveshaft's bearing or the diff - for noises.

Dack

[doogee]

You're definitely overthinking this.

Takes a few steps back and have the typical culprits checked.

[pbonsalb]

Very in depth analysis. I will try to look at mine next time it is on the lift to see which version I have.

[DR-JEKL]

Originally Posted by Dackelone

Perhaps its something more simple/common like a bad center driveshaft (support)bearing that bad?

#8 in your parts diagram.

Have you tried putting your car up on a lift and driving it up past 80 kph and have a tech or two under the car to look to see whats moving/vibrating. They could use a mechanic's stethoscope to probe the driveshaft's bearing or the diff - for noises.

Dack

Thanks for your reply Dack!

AFAIK the original centre bearing was re-used, so I would assume since it was fine before the driveline upgrade it would be OK now? I reside 2hrs away from the workshop so unfortunately cannot really drop in and witness for myself

I had the shaft sent out to a 2nd driveline specialist as the initial shop their balancing machine couldn't spin the shaft at a high enough RPM to see any vibration or balancing issues

[DR-JEKL]

Originally Posted by doogee

You're definitely overthinking this.

Takes a few steps back and have the typical culprits checked.

Hmm yup most likely, I thought of having the car up on a trolley jack and running it up to speed and having a squiz under the car albeit would be a tad dangerous to get under the car... Touch wood the 2nd shop balancing the driveshaft cures the issue!

Originally Posted by pbonsalb

Very in depth analysis. I will try to look at mine next time it is on the lift to see which version I have.

Cheers, this thread was posted to raise the awareness of the counterbalancing bolts/washers for you ///M owners as a heads up if you ever get work done on your diff to be mindful of it. Unfortunately I had no idea and never checked my diff before installing it

[SYT_Shadow]

Unfortunately I can't help you, but the information is very interesting!!

[DR-JEKL]

Originally Posted by SYT_Shadow

Unfortunately I can't help you, but the information is very interesting!!

Cheers

The main reason for this post was to see if anyone else has any knowledge or experience with this counterbalancing bolts/washers and to raise the awareness for guys who may not know

[DR-JEKL]

FYI marconi118

[Bx Tpr]

Could this explain why guys are having humming noises with the CF driveshaft? Placing the colored bolts where they aren't supposed to be during install? Or do carbon driveshafts usually hum?

[DR-JEKL]

Originally Posted by Bx Tpr

Could this explain why guys are having humming noises with the CF driveshaft? Placing the colored bolts where they aren't supposed to be during install? Or do carbon driveshafts usually hum?

AFAIK its common trait to have added NVH with a rigid one piece cf prop due to the shaft itself.

[DR-JEKL]

The black and green bolts are counterbalance bolts, whereas the silver is a normal ///M diff flange bolt.

It seems the only difference is the thread is longer on the counterbalance bolts (I'm guessing they're actually lighter than normal bolts) and are applied in the location of imbalance. I'll have to weigh them in the wifeys kitchen scales to confirm!

[squartus]

Originally Posted by Bx Tpr

Could this explain why guys are having humming noises with the CF driveshaft? Placing the colored bolts where they aren't supposed to be during install? Or do carbon driveshafts usually hum?

All the bolts in my oem drive line were the same color/size. As were the bolts that came with the CF drive shaft. Sucker does hum though, course its solid and has no rubber guibo and solid rear diff mounts.

[07tundra]

so the diff I got was from an 08 M3 it has a blue paint mark on the outside. From reading above I need a washer? But where exactly (which hole) do I use the washer in? Is it like the pic shows above?

[DR-JEKL]

Originally Posted by 07tundra

so the diff I got was from an 08 M3 it has a blue paint mark on the outside. From reading above I need a washer? But where exactly (which hole) do I use the washer in? Is it like the pic shows above?

You're system B and yes in hole that is marked blue on diff flange:

[07tundra]

Originally Posted by DR-JEKL

You're system B and yes in hole that is marked blue on diff flange:

Now Where or how do i get this washer?

[DR-JEKL]

Originally Posted by 07tundra

Now Where or how do i get this washer?

email ECS FCP, a mate got his from FCP

[07tundra]

Originally Posted by DR-JEKL

email ECS FCP, a mate got his from FCP

Maybe I'm not asking correctly but none of them know what i'm talking about this frustrating

[DR-JEKL]

Originally Posted by 07tundra

Maybe I'm not asking correctly but none of them know what i'm talking about this frustrating

Did you email them this image? (it states refer to electronics parts catalogue MG26)



A mate ordered his about 12 months ago!

[kamber]

Thanks for doing all the legwork on this btw, DR-JEKL. I referenced this thread many times before buying my M-Factory CF driveshaft a few months ago. Still havn't gotten around to installing yet, but I'm System B according to the production year, and hoping to the correct washers will already be on there and that I can just replace the bolts/nuts while reusing whatever washers came on my car originally.

[07tundra]

Originally Posted by kamber

Thanks for doing all the legwork on this btw, DR-JEKL. I referenced this thread many times before buying my M-Factory CF driveshaft a few months ago. Still havn't gotten around to installing yet, but I'm System B according to the production year, and hoping to re-use the correct washers will already be on there and just replace the bolts/nuts.

I will 2nd that comment I've bugged you a lot and you keep responding, so many thanks!!

[07tundra]

This is what I was told by FCP


Below you will find a direct link for the rear diff fluid, the part number will be 83222282583. With the washer, it's not that we don't want to source it for you, we are unable to. The part number you need, 26102284017, is not available for purchase. My sincerest apologies that we are unable to assist wit that request.