HELP: 4.10 medium case LSD on 1991 318i sedan

[Narsiyousif]

Hi everyone,
I have a 1991 318i sedan (m42) I recently replaced my diff to (4.10 medium case LSD) and serviced the manual transmission and did the 5 lug swap and changed the center support bearing for the driveshaft
now when I am driving it I have a vibration that starts when I hit 70 mph and higher (more speed more vibration ) the worse at 80 mph and when I turn there is a clicking noise in the rear driver side !!
decided to take the driveshaft apart to check the alignment marks and it is aligned according to the manufacture white dots / it use to drive smooth before doing all this work :(
I noticed that the diff is sitting to the right of the subframe (passenger side) is that normal? and anything that I need to check while I have everything disassembled to check for the vibration?
I attached some photos showing the driveshaft

[bmwman91]

Did you bias the CSB forward 5mm as required by the service manual? The rubber web needs some pre-load to function as intended.

As far as the diff seeming to be offset, I am not sure since I don't have a medium case diff installed.

Since you did a 5 lug conversion, are you running used wheels? It could very well be that one or more of them is bent or unbalanced, or something is up with the tires if they are also pre-used. Getting a wheel straightened is fairly inexpensive.

[Narsiyousif]

all wheels are straight and new tires everything was balanced before install , the CSB was pre loaded , took everything a part yesterday and found the CSB bearing had some play ! so i ordered new one (Febi) I dont know if that is the problem or something else got the CSB bearing to have some play , i have new engine mounts, new transmission mount almost and the subframe bushings all was replaced not long ago 😞 i will try the new csb and hope that will fix it , thanks for the reply

[bmwman91]

Aah, yeah it sounds like you probably found the culprit.

[TobyB]

I have had bent flanges on diffs do that-

it imbalances the driveshaft, and gives all sorts of awful driveline vibrations.

Easy to check- pull the driveshaft, and run a dial indicator on the machined surface.
There should be 0.00mm of runout. Usually, you'll see a 'divot' or a bent ear if this has happened.

If the diff gets dropped on its flange, they bend pretty easily.

I've also had loose pinion bearings manifest as a vibration, too, as
that causes a similar imbalance. There should be just a little
preload on the bearings when you turn the pinion.

just 2 things to check,

t

[Narsiyousif]

I have had bent flanges on diffs do that-

it imbalances the driveshaft, and gives all sorts of awful driveline vibrations.

Easy to check- pull the driveshaft, and run a dial indicator on the machined surface.
There should be 0.00mm of runout. Usually, you'll see a 'divot' or a bent ear if this has happened.

If the diff gets dropped on its flange, they bend pretty easily.

I've also had loose pinion bearings manifest as a vibration, too, as
that causes a similar imbalance. There should be just a little
preload on the bearings when you turn the pinion.

just 2 things to check,

t

ok, let me give more details I have the car for over 4 years I use to drive it for a long time with open diff it was really smooth and 0 problems one day I decided to refresh the rear subframe replacing all bushings and added the subframe camber and toe kit from Garagistic and I replaced the CSB too after that day I started noticing small vibration, now that I have been working on the car for more than 6 months restoring it and add LSD and the vibration now is amplified for some reason i matched the factory dots on the drive shaft, transmission mount are new, new engine mount, almost everything new in the drive train, rc090 all checked restored and new tires, rebuilt CV joints in the axle shafts now boots , all new bearings and hubs all around and checked after installation for play and 0 play the u joints on the drive shafts are smooth and no play the only small play found was in the CSB but it was really small play idk if that is the main problem or there is another problem causing the CSB to have play placed order for most of the component for drive shaft as shown in attachment and i will see what will happen and today i will do the flange check with a dial indicator that is a great point here thanks for the suggestion i will let you know the results

[TobyB]

add LSD and the vibration now is amplified

Did you disturb the pinion bearing to add the LSD center?

Or change the whole case?

If either, then I'd look at the diff input and see if something's goofy there.

hth

t

[Narsiyousif]

Did you disturb the pinion bearing to add the LSD center?

Or change the whole case?

If either, then I'd look at the diff input and see if something's goofy there.

hth

t

i bought a good clean medium case LSD 4.10 and replaced the whole thing i had small case open diff before that come standard in 1991 318i sedan but yea iam not sure if the diff input shaft should be centered in the middle of the subframe opening or it is always shifter to the passanger side , it will help if someone can just take a look at their diff input shaft if it is centered or not then i would know if that is a normal thing or not , and yes I check the input shaft and the output shafts with a dial indicator and everything look fine when it is spinning stayed on 0 i just received the parts i ordered today and tomorrow i will be installing the parts i hope that will fix the problem 😔

[Narsiyousif]

i just finished installing all the new parts that i ordered from FCP euro and test drive it, still shacking and vibrating at 80 mph :( , what do you guys think it is maybe it is something not related to driveshaft ?!

[bmwman91]

I looked through some old pictures of my diff when I had it out, and the input flange is definitely offset a bit to the left (if you are looking at the flange). Your diff should be positioned fine...if it was so messed up that the input shaft was out of place, it would be obvious I think.

You mentioned rebuilt CV axles. Who rebuilt them and where did you get them? I bought rebuilt "OEM" GKN axles from ECS for my TDI Jetta and they were junk straight out of the box. Crazy vibration and clunking, and when making left turns the car felt like it was going to come apart. As many others on here can attest, a LOT of the rebuilt axles for the E30 are also crap, regardless of how much they are hyped as "OEM" quality. You either have to find new-old-stock ones, or keep swapping rebuilds until you get good ones. In the case of my Jetta, I just returned the duds to ECS and had proper rebuilds made by Raxles. They are super reputable, stand behind their product and seem to do rebuilds the proper way. I am not sure if they do E30 parts, but you could give them a call to ask about your problem to see what they think.

https://www.raxles.com/

[Narsiyousif]

I looked through some old pictures of my diff when I had it out, and the input flange is definitely offset a bit to the left (if you are looking at the flange). Your diff should be positioned fine...if it was so messed up that the input shaft was out of place, it would be obvious I think.

You mentioned rebuilt CV axles. Who rebuilt them and where did you get them? I bought rebuilt "OEM" GKN axles from ECS for my TDI Jetta and they were junk straight out of the box. Crazy vibration and clunking, and when making left turns the car felt like it was going to come apart. As many others on here can attest, a LOT of the rebuilt axles for the E30 are also crap, regardless of how much they are hyped as "OEM" quality. You either have to find new-old-stock ones, or keep swapping rebuilds until you get good ones. In the case of my Jetta, I just returned the duds to ECS and had proper rebuilds made by Raxles. They are super reputable, stand behind their product and seem to do rebuilds the proper way. I am not sure if they do E30 parts, but you could give them a call to ask about your problem to see what they think.
https://www.raxles.com/

yea exactly i found some photos online showing that the diff is offset to the passenger side so i know now that is not a problem. for the CV axles i did rebuilt them myself I paid crazy attention to details which I didn't have to but I did anyways to the point that i took ton on photos and put every single component in a separate container and did one axle at a time changed the boots and used (Red Line 80401 CV-2 Grease), the vibration was present even before starting the whole car rebuilt . i think it started when i changed all the bushings for the rear subframe and added camber and toe adjustment from garagistic but the vibration was lighter now it feels dangerous when i hit 80 mph

[Narsiyousif]

you won't believe it I think I found the problem, I did the 5 lug swap and I used the e46 m3 hub for the front and Z4 hub for the rear and I am using e39 RC090 wheels, and even though I can't see the difference in the center bore visually but yes there is a difference because the e46 and z4 hubs have 62.6 mm center bore and for the e39 is 74mm so there is 1.5mm difference and yes it does make big difference in high speed because the wheel is not centered when it is mounted so I ordered the Hub Centric Rings and I hope that will fix the problem if not then I will mount the 16" e38 style 5 wheels I know it was a stupid mistake and I relied on my visual and didn't check the center bore for the e39 wheels but yea that is how we learn, thanks to everyone who commented and helped really appreciate you help ✌

[bmwman91]

lol

Well, I am glad you found the issue. That will certainly do it.

[ForcedFirebird]

Was thinking out my reply, then you found it lol.

Some notes:

The diff is offset in the chassis, I don't go by the tick marks when assembling drive shafts, since many shaft halves have been mixed and matched on many cars by this age - all you need to do is make sure the universals are in the correct orientation (they actually have two positions 180° apart). If they are one or a few splines off, they tend to vibrate at specific speeds, if they are 90° out the vibration will be consistent and will get worse with speed.

The CSB preload is only to keep the bearing from coming out of the rubber support. It has zero effect on vibrations, I have personally tested this to the race car's terminal speed (147mph on GPS). If you don't preload the carrier, then the bearing has room to move back and forth in the rubber carrier - in fact you can change the carrier in an e30 without removing the bearing - I rarely see a bad bearing, it's always just the rubber that dry-rotted or ripped. Either way, if the circlip is on the bearing, preload is kinda moot IMO. Later models like e36 have the carrier behind the bearing.

The giubo has arrows on it. Those arrows MUST face the flanges, or the giubo will be strong in reverse gears, and weak in forward gears - every other bolt pair on the giubo has a thin web between. Those thin webs are for tension, the thick ones are for compression (just think about the engine rotating the giubo and you it's easy to visualize). Countless times at work we have had to change customer-installed giubos since they couldn't figure out why their giubos were lasting a few weeks at a time.

[Narsiyousif]

Was thinking out my reply, then you found it lol.

Some notes:

The diff is offset in the chassis, I don't go by the tick marks when assembling drive shafts, since many shaft halves have been mixed and matched on many cars by this age - all you need to do is make sure the universals are in the correct orientation (they actually have two positions 180° apart). If they are one or a few splines off, they tend to vibrate at specific speeds, if they are 90° out the vibration will be consistent and will get worse with speed.

The CSB preload is only to keep the bearing from coming out of the rubber support. It has zero effect on vibrations, I have personally tested this to the race car's terminal speed (147mph on GPS). If you don't preload the carrier, then the bearing has room to move back and forth in the rubber carrier - in fact you can change the carrier in an e30 without removing the bearing - I rarely see a bad bearing, it's always just the rubber that dry-rotted or ripped. Either way, if the circlip is on the bearing, preload is kinda moot IMO. Later models like e36 have the carrier behind the bearing.

The giubo has arrows on it. Those arrows MUST face the flanges, or the giubo will be strong in reverse gears, and weak in forward gears - every other bolt pair on the giubo has a thin web between. Those thin webs are for tension, the thick ones are for compression (just think about the engine rotating the giubo and you it's easy to visualize). Countless times at work we have had to change customer-installed giubos since they couldn't figure out why their giubos were lasting a few weeks at a time.

great information i will save this comment for future projects thank you.