Rear differential question.

[jason635csi]

Its my 1st time posting here so be ready for some newbie questions. I've got a gray market '84 635csi and have a few questions.
1st of all, there is a roar in the rear diff that has me concerned. It only occurs when I'm accelerating or decelerating when the car's in gear and clutch is engaged. If the clutch pedal is depressed and the car's rolling, there is no noticible noise. Any ideas on which bearing I'm looking at needing to replace? Also, would it just be easier to replace the rear diff from a parts car? Would one from a 7 series fit?
2nd, I have 15" Rial wheels with 225-60/15 Yoko AVS intermediates and they rub the front wheel wells when turning. I'm sure it doesn't help that the car is lowered on Bavauto sport springs but I'm just wondering what size tires everyone else here uses. I was thinking of just replacing the front AVS's with a comparable tire (thinking AVS ES100) in possibly a 225-50/15 size. Any comments?
3rd is a general question....where is a good place to source used parts for this car? I need some rear speaker pods (I'm guessing this is common), some HVAC controls, and assorted other crap.
Thanks!
Jason Mawhinney
'84 635csi
'70 MGB
'85 Audi 4000 quattro 20v
'87 Audi 5000 turbo quattro

[KC Ron Carter]

The differential is not a big deal.

The late model e24 uses the same model and size differential as the e30 6 cylinder, Z3, or the e28, with an output shaft swap and an aft face plate swap. The output shafts are a friction lock that can be poped with a screwdriver.

If yours is a gray market car it should be a 3.07 to 1 ratio.
Look for a tag on tha aft face plate on the differential.

The USA cars all have a higher ratio and that provides a bigger torque curve for better performance.

The ratio are 3.25 to 3.73 on the e24 635csi.

The ratio on the M series is 3.90 to 1 and it uses the larger chunk of the seven series, e23.

But you can get a 3.73 or a 3.90 to 1 from a e30 and I will promise a difference you will not believe.

I use a 205.60x15 tire also and mine uses a 21mm offset.
No rubbing anywhere or anytime.

Got the springs from Bavarian Autosport.

I used the Bilstein Sports and the second spring perch up on the rears.

That gave me an effective drop of 1.5 in the front and 1.7 in the rear. The tire size is very important in any suspension setting and mine are the Yokahama 205.60x15. I also have the complete Paul Gray synthetic bushings in the front.

Here is my close up picture and I have hand space all around and no rubbing ever. I have the tirerack hub centric spacers on these wheels since the hub size on the later models is larger. These are the BMW OE wheels and are polished and not chromed.







Later,

[calereeves]

I've got a complete 80 635 parts car with a good differential, if you're interested. Also, if you want some new wheels, I've got some 16" MOMOs with great tires.


http://community.webshots.com/user/calereeves

There is a BMW folder on there with pics of a lot of the parts.

[jason635csi]

Thanks for all the info!
KC Ron Carter, that's a very helpful wealth of knowledge. I may mess with the rear diff's ratio if it really is that beneficial.
calereeves, thanks for the offer on the parts. I'm not real sure I'm into that style of Momos but they're certainly period correct and look like they're in good shape. I'll consider them. I may be interested in the diff. Any idea what the ratio is? BTW, where are you located to have palm trees and snow on them? Betcha that's a rare sight!
Jason

[calereeves]

Jason, I'm not sure of the exact ratio, but I want to say they are either ~3.23 or ~3.73. I know it is a limited slip rear though. I will have my dad check tomorrow. The car is back home in Texas, where I took the pic of the palms covered in snow. That was taken on Christmas day, after 8 inches of snowfall, the first time EVER in houston history that we've had a white christmas!!!

I'm now back in Colorado Springs, CO at school, so I'll have to have my dad check on the gear ratio tomorrow.

Cale


email me at C08Trenton.Reeves@usafa.af.mil for more info.

[KC Ron Carter]

Just a note of caution:

The 1976 through 1982 e24 is based on the e12 and uses a side loading differential. The later models use a different differential.

Later,

[slyhog-22056]

Going through the same thing I did. I removed my diff and pulled the bearings. BMW bearings are expensive, but... there is american crossover All the bearings and seals for my 84 633CSi cost a whopping $69 total, rebuilt the entire rear end in less than 1 day and got rid of that anoying noise for good, when you disassemble it DONT mix up the side shim plates from 1 side to another, they set the side thrush bearing clearances. I got my bearings from Applied Industrial Bearings

[jason635csi]

Thanks again for all the info! I may actually just rebuild the one I have if it doesn't take all kinds of expensive BMW specialty tools. Slyhog, how did you determine what bearings you needed? Did you take apart the diff and cross reference the numbers or did the place you order from have all the part #s? I'd love to rebuild what I have. I do really like getting in there and learning about all the inner workings.
BTW, is a Bentley manual the only way to go or can you get by with a Haynes/Chilton? Thanks!
Jason

[slyhog-22056]

Then manuals arent of any help at all, I removed the bearings and cups and seals and took them to Applied Industrial and they made a few calls and found out the the part numbers are the same except for having to drop either the prefix letter or last one, dont remember for sure. The only "specialty tool I needed was a press to remove and press on the new ones, took about 2 hours at the most and had everything apart and back together in a little over 4 hours. It took me longer to get the metric allen screws out of the half shafts than remove the rest. Get in there with all of it dont be scared to tear anything apart, I love being able to tell people I either done it my self or fabricated something instead of paying or buying things

[calereeves]

What are the side loading diffs worth? I've seen the rear loaders on ebay for about $250, but I've never seen a limited slip side loader for sale.

About what are they worth?

[slyhog-22056]

What are the side loading diffs worth? I've seen the rear loaders on ebay for about $250, but I've never seen a limited slip side loader for sale.

About what are they worth?

They arent side loading diff's, they are side loaded bearings, meaning the bearings are held together with spacers on the side covers, you still have to remove the pinion gear from the rear although they are a lot easier that standard diffs. as far as limited slip mine isnt, it used spider gears like most others but for some reason it is almost impossible to just light up 1 rear tire, it always spins them both even in hard cornering, lots of fun ....sometimes

[calereeves]

They arent side loading diff's, they are side loaded bearings


Actually the diff that came out of my car has a cover on the side where you would take the carrier out. There is no cover on the rear. To pull the ring gear carrier out, you would have to take off the driver's side axle and unbolt the cover around the driver's side output shaft.

I haven't seen any of these on ebay or anything of the like before...


cale




see a picture at

http://files.automotiveforums.com/ga...cat=500&page=1

[slyhog-22056]

I have seen those before.... back in my sprint car driving days. Never really knew what they came out of, but now I guess I do. Are you trying to sell it or replace it??? If you are trying to replace it I can look around hear at some of the U-Pull It yards and maybe find you one. There seems to ba an abundance of the late 70's and 80's BMW Euro versions around here (Dallas-FtWorth area) for some reason

[inkfreak74x9]

I dont know if you got yours fixed or not but I have one sitting in my garage. It is in excellant sondition, Just resealed and gear mesh is perfect and gears and bearings pristine. Willsel cheep. Contact me at inkfreak74x9@yahoo.com