Differential swap [Archive] - Bimmerforums

clevertd

11-19-2007, 04:29 PM

attack eagle

11-19-2007, 05:01 PM

swap the seals? check if the flanges are the same as the e34?
shrike found that in his swap they were not so he had to swap output and input flanges between cases.

If you do swap the output flange seals, I would be most interested in the PN and any coverage or illumination you can provide as I will need to do this to my 3.23 LSD

Mr Project

11-19-2007, 05:41 PM

The main trick with the input flange is to have a 30mm thin-wall socket handy. My 'normal' 30mm socket won't fit down in the valley to get to that big nut.

The output seals are EASY, just pop the 'hubs' out with a screwdriver or similar, replace the seal, and pop them back in.

clevertd

11-19-2007, 07:38 PM

I stumbled across a few posts regarding the replacement of the speed sensor. Any sense in buying a new one when my old one works fine?

EDIT: When replacing seals, do you mean with new parts?

Binjammin

11-20-2007, 02:29 AM

I stumbled across a few posts regarding the replacement of the speed sensor. Any sense in buying a new one when my old one works fine?

EDIT: When replacing seals, do you mean with new parts?

Why would you replace anything with old parts?

Seriously though, you'll need to change your input flange, I did a diff swap alone one night and found that one out the hard way. Wrestled the damn thing in myself with the car on the lift only to find out I could have saved a ton of work with the diff out of the car... doh.

Mr Project

11-20-2007, 07:50 AM

Clevertd, if your speed sensor is working, I'd leave it. They do go bad, but I don't think you have to drop the diff out to replace one on an E34.

Goathumper

11-20-2007, 12:26 PM

mine still has the 3.91 from the auto and i almost craped me pants when the driveshaft slid right in. From all the sources i read, it said the manual tranny cars had the larger 1xx mm hub with m10 bolts. That was the case on my 525i but not 535i :confused.

cary

11-20-2007, 04:03 PM

I picked up a 3.91LSD off ebay out of a 735i. 94K miles. Aside from the fluid being changed, is there anything else I should do while swapping it out? Anyone have any pointers as far as expected time and tools needed? I'll continue searching to see what other pointers have been said in the past... but I'm definitely looking forward to seeing what this does for my car:D

Just my thoughts on how it works. I had a 3.46, put in a 3.91 and now have a 3.64. The 3.91 makes the thing pull like a freight train out of the hole. The problems I had with it were 1) I was constantly in 4th gear around town, and 2) it drove me nuts on the freeway. The 3.91 I got also leaked and growled, sealing its fate.

Goathumper

11-20-2007, 04:37 PM

no kidding about the highway speeds. I found myself cruising at about 3.5k. Just enough to be annoying.

Mr Project

11-20-2007, 06:23 PM

Complaining about 3.91s? Pansies. :) With 4.10s behind an m30 5-speed, I start in second, shift to 5th at 30mph, and I'm done.

attack eagle

11-20-2007, 08:06 PM

Lol... I can't wait to do that.

clevertd

11-21-2007, 02:08 AM

Thanks for the input everyone. I just got home, and this thing is freakin heavy. It looks like some oil leaked out onto the box it was shipped in, replacing that regardless (just not sure which kind yet as I've heard conflicting opinions about what's needed for a LSD), just want to make sure that it won't leak once it's in the car.

Binjammin - I think I worded my question in a dumb way. Is it necessary to replace them with new parts before swapping the differentials out?

To buy: 30mm thin wall socket, 14mm allen wrench, fluid

clevertd

11-21-2007, 02:30 AM

Came across a post on bimmer.info from gale circa 2004,

e32/e34 diff's will interchange but I believe M5's are different. You may have to swap the input hub and/or axle output hubs depending on the year and whether the diff is from a manual or auto. I believe only lsd to lsd axle hubs can be swapped, open diff's have a different arrangement for how the hubs attach and are attached internally? Lsd hubs come off really easy, just pry on the outer flange lightly with a screwdriver and it pops an internal snap ring out of a groove. Just be careful to put them back in lightly and rotate them slightly to register the splines before tapping them in with a rubber hammer. Replace the seals if the hubs have to be removed.

The diff is really easy to remove from the car. The socket head screws on the axles are a pain to break loose the 1st time. They have serrated binder heads on the underside of the head which bites into a metal washer plate that spans 2 bolts. Clean any dirt out of the sockets with a small screwdriver & compressed air & use a breaker bar on a hex bit or a pipe on an allen wrench. The diff drops out by removing the 2 bolts on the rear bracket and the single bolt on the front of the stamped sheet metal plate. The plate stays on the diff. The diff is heavy, it weighs approx. 92# so be ready with a floorjack.

It might get a little dicey if you have to swap the input hub, the preload on them is factory set and establishes the clearance between the ring & pinion gears. If merely removing the hub to replace a seal, and putting the same hub back on, one can scribe a mark on the nut & hub & retorque it to the same position. You might be able to successfully swap them if you scribe a mark and measure the torque required to line the mark back up, and apply that torque to the swapped hub & neglect the mark. If the preload isn't set correctly, the diff can fail within 1000 miles.

clevertd

11-21-2007, 02:44 AM

Part number 33 10 7 505 602 is the shaft seal with lock ring. It is used for quite a lot of vehicles. See here for full list: http://bmwfans.info/part-33107505602/

Also, some more tips from another thread (courtesy of Robin-535im):
1) Get a stiff wire brush and clean all the crud out of the torx bolts that hold the half shaft to the hub & to the diff output flanges. They get filled in with years of road grime and often they are really tight. When you stick the torx driver in, it compresses the crud to the bottom of the hole and you think you have a good grip on the bolt... but you soon realize how easy it is to strip torx bolts! I reused all my bolts and put on a little locktite blue (medium strength). Cleaning the crud makes reassembly peaceful and pleasant. If you're flexible (and use a u-joint + extension on the socket wrench), you can get all six out per joint without rotating the wheels, hence you can keep the p-brake on and do the job in one sitting.

2) get new output shaft seals, see the recent post... pretty easy to change them and they're only a few bucks.

3) change the big rear carrier-to-car bushing while you're in there, the one right up against the gas tank. Not required, but if you're changing things out anyway it's a good time to do it. It's one of those things on Bill's list-of-things-that-break on E34's.

4) check your half-shafts for play when they're out. Grab one end and twist the other back and forth. Good ones will have no play, mediocre ones will have a slight click & a little tiny bit of play. They're not too pricey, maybe $80 a side? If you're getting a new tranny anyway, might as well get all the slack out of the drive line you can. You'll appreciate the mental satisfaction that the driveline is as tight as a new car.

Goathumper

11-21-2007, 09:22 AM

on another note, it may be safer to swap flanges on your driveshaft if you need to.

clevertd

11-25-2007, 01:41 AM

How in the world do you get the output seals out? Bentley states to pry old oil seal from its recess using a hooked seal removal tool or a large screwdriver.

attack eagle

11-25-2007, 03:03 AM

Since there is a lock ring, and a seal, I would assume with a hook tool you would pull the lock ring out of place and then the seal... but I obviously haven't done mine yet. Betcha shrike071 knows since he swapped flange. He seems like the type of fellow to do them preemptively.

clevertd

11-25-2007, 04:09 AM

http://forums.bimmerforums.com/forum/showpost.php?p=9353646&postcount=34

He doesn't mention it

Binjammin

11-25-2007, 04:39 AM

Also, some more tips from another thread (courtesy of Robin-535im):
1) Get a stiff wire brush and clean all the crud out of the torx bolts that hold the half shaft to the hub & to the diff output flanges. They get filled in with years of road grime and often they are really tight. When you stick the torx driver in, it compresses the crud to the bottom of the hole and you think you have a good grip on the bolt... but you soon realize how easy it is to strip torx bolts! I reused all my bolts and put on a little locktite blue (medium strength). Cleaning the crud makes reassembly peaceful and pleasant. If you're flexible (and use a u-joint + extension on the socket wrench), you can get all six out per joint without rotating the wheels, hence you can keep the p-brake on and do the job in one sitting.

I'd avoid using a universal when taking out the half-shafts. It seems like a no-brainer to use it to avoid having to turn the wheels, but a u-joint will make it a million times more easy to strip out a torx bolt if you're not careful, you want all the torque you're applying to be on the center axis of the bolt. Universals make it difficult to judge that. I always break the bolts free one at a time by spinning the wheels, then can go around and loosen them all easily after that.

+100 for cleaning out the bolt heads beforehand. Torx bolts are great, whish they never existed :)

Yeah, new gaskets and seals are a good idea to throw in before you put it in the car, throw a new seal on the rear cover too if it's leaking.

Mr Project

11-25-2007, 09:23 AM

How in the world do you get the output seals out? Bentley states to pry old oil seal from its recess using a hooked seal removal tool or a large screwdriver.

The output seals are just pressed-in oil seals like any other...I just take a big screwdriver and maybe some pliers and pull them out. I almost always destroy them in the process, but it's not like you're planning on using the old seals for anything, right? :)

Just take care to not mar the seal surface of the diff itself. Then just use a large socket or correctly-sized block of wood and a hammer to tap the new seals into place. No big deal.

clevertd

11-25-2007, 10:47 PM

http://home.comcast.net/~matthew.c.smith/mods/diff_output_shafts/index.htm

I'm not a weak person by any means, but these things aren't budging:help. Maybe find someone with a torch...

cobb 535

11-26-2007, 05:47 AM

I picked up a 3.91LSD off ebay out of a 735i. 94K miles. Aside from the fluid being changed, is there anything else I should do while swapping it out? Anyone have any pointers as far as expected time and tools needed? I'll continue searching to see what other pointers have been said in the past... but I'm definitely looking forward to seeing what this does for my car:D
Just curious - I have a 3.91 LSD in my 89 535 parts car. I do not know it's value. How much did you pay from E Bay if you don't mind telling.
Thanks

bam2002

11-26-2007, 07:19 AM

Does any one know what the choices for the ratios would be?
I was planning to rebuild the whole rear axel/ subframe off a parts car then swap it into my 1991 e34 5 speed. The parts car was an Auto so I figured it have at least a ratio in the hight 3's. It appears to have a 2:75?
I have not checked my other auto parts car or the 5 speed car yet. Ill check the 5 speed car today. Usually on e30s all the auto cars where geared with 3:9s or 4:10s. I am suprised to see its not so on the e 34s.

Thanks
B

5271990

11-28-2007, 09:01 AM

Usually on e30s all the auto cars where geared with 3:9s or 4:10s. I am suprised to see its not so on the e 34s.

Thanks
B

Some were. M30 autos had the 3.91 and M20 auto's had the 4.1.

There were 5 different base engines used in E34's and there were variations in most of them with different bores/strokes and technical updates which had various combos of tranny's and diffs.

Clevertd did you do the swap yet????

As stock this thing doesn't come on cam in 5th until 90mph :devillook, (ab)using 3rd gear does the trick but....... hows the new diff :confused

Fishtailing in the rain is pretty freaking scary with the stock ratio!

TouringDan

11-28-2007, 09:16 AM

The output seals are just pressed-in oil seals like any other...I just take a big screwdriver and maybe some pliers and pull them out. I almost always destroy them in the process, but it's not like you're planning on using the old seals for anything, right? :)

Just take care to not mar the seal surface of the diff itself. Then just use a large socket or correctly-sized block of wood and a hammer to tap the new seals into place. No big deal.

Sorry - just saw this thread. He's correct - at least on the diff I have. I did replace all the seals and they do pop out, although do NOT hold any hopes of keeping them around. They will be destroyed in the process. I have a seal-tool that I've owned for ages. It looks like a giant paint-can opener, if you know what those look like. It took some trial-and-error in regards to proper placement of a piece of wood for leverage, but after a bit they came out. One thing you can do is carefully pull off all the actual 'seal' and then use a set of needlenose pliers to pull the metal part of the seal away from the case to loosen it a bit.

As far as ratios go - I think that Attack Eagle has a near perfect ratio for a 1:1 final drive. (3.23, if I am not mistaken...). A 3.64 is a bit too high for my tastes. I am at 4k at 80.

clevertd

11-28-2007, 01:18 PM

Clevertd did you do the swap yet????

I haven't had any free time, four tests this week, graphic design project due monday, and a couple days of work in between. Drove to Charlotte last night and back this morning for orthodontist, got an OBC indicated 26mpg (I stayed away from 80mph and 3k RPM:stickoutt).

Sorry - just saw this thread. He's correct - at least on the diff I have. I did replace all the seals and they do pop out, although do NOT hold any hopes of keeping them around. They will be destroyed in the process. I have a seal-tool that I've owned for ages. It looks like a giant paint-can opener, if you know what those look like. It took some trial-and-error in regards to proper placement of a piece of wood for leverage, but after a bit they came out. One thing you can do is carefully pull off all the actual 'seal' and then use a set of needlenose pliers to pull the metal part of the seal away from the case to loosen it a bit.

Thanks for the input:buttrockHoping to get this done whenever I get a minute to breathe.

Isaacus

11-28-2007, 01:38 PM

When I swapped my diff in my 525i (twice) I found out after the first time that you're much more likely to break those axle bolts out without stripping them if you do two things:

1) Spray the hell out of them with PBlaster or WD40 first.

2) Hammer an 8mm allen socket into them, then break them loose. It does two things: Breaks rust on the seized threads through the repeated direct blows, and makes sure the socket is completely in there.

If you don't do those two things, there's about an 80% chance any given bolt will strip. And do NOT use a universal joint with your tools. Just keep rotating the axle and pulling the handbrake to hold it in a spot where you can reach it with a straight extension.

BTW I swapped from a 3.73 to a 4.10 and won't really be going back unless I turbo the car. I don't mind the revs on the freeway much. It's an inline 6. They're as well balanced as it gets.

5271990

11-28-2007, 05:24 PM

I haven't had any free time, four tests this week, graphic design project due monday, and a couple days of work in between. Drove to Charlotte last night and back this morning for orthodontist, got an OBC indicated 26mpg (I stayed away from 80mph and 3k RPM:stickoutt).

I hate to admit it in public but I feel like a d!ck.I finally got around to installing the sparkplugs, fuel filter and air filter I've had sitting in the trunk for 3months. Even beating the piss out the car I now average 28mpg (drive gently 35mpg :eek:) as opposed to 20mpg (UK gallons not U.S.). I've wasted ~$500 worth of fuel because I avoided the simple maintenance.......

Honestly I don't understand the point of the stock E34, its seems like its for business men who like to cruise at 100mph+ and drift around high speed corners. I don't understand it but I love it :D:D:D

attack eagle

11-28-2007, 08:31 PM

yeah, I feel you.
After over a year, I may finally get around to fitting a new fuel filter since I will be under the car anyway for the trans change.

attack eagle

11-28-2007, 08:40 PM

As far as ratios go - I think that Attack Eagle has a near perfect ratio for a 1:1 final drive. (3.23, if I am not mistaken...). A 3.64 is a bit too high for my tastes. I am at 4k at 80.

:D 3.23 LSD (even bettah!!!)

So looking forward to finally getting time to place my order with patrick, and getting time to work on the car again. With 3 history essays due Tuesday, a communications observation due Tuesday, a web project due on Tuesday, and a Feature article due tommorrow at 10:30 am... well I'm almost glad I don't have parts to distract me.
As long as it is done before Xmas eve so my eldest boy can sit in my lap and drive around the closed off neighborhood light show, I'm happy. It is the one time of the year that he can safely do what many of us got to do routinely back in the "good old days".

clevertd

12-08-2007, 10:45 PM

http://www.bmwe34.net/E34main/Maintenance/Transmission/Differential_seals.asp

How I forgot to consult the E34 Bible, I will never know. I still haven't had room to breathe, but at least this will help.

attack eagle

12-09-2007, 03:16 AM

Good deal. I guess I might as well do the diff. at the same time now that I am not SUPER pressured for time... and it looks like I can do the seals in a couple of hours. Good find,I had never run across that one on the site b4.

bmwpower

12-09-2007, 07:43 AM

So if I have a 3.91 LSD in my 535iA and I want better gas mileage, I would change to 4.10 LSD? Is that correct? How much acceleration am I going to lose?

TouringDan

12-09-2007, 07:46 AM

No - the 4.10 will give you worse mileage, but faster acceleration. Drop down to a 3.64, 3.46 or 3.23. Remember - the lower the number, the higher the gas mileage/slower the car.

bmwpower

12-09-2007, 07:49 AM

No - the 4.10 will give you worse mileage, but faster acceleration. Drop down to a 3.64, 3.46 or 3.23. Remember - the lower the number, the higher the gas mileage/slower the car.

Got it. I must not have had my coffee yet... Thanks!

attack eagle

12-09-2007, 08:16 AM

you generally get the best mileage (IMO) when you cruise somewhere in the rpm range where you could make within 80% of peak torque if you went WOT. peak torque is generally peak efficiency.

this is why hondas and other low torque engines have high rpm at cruise compared to a big displacement engine.

I guess in other words, don't go crazy and think that if you have an m50 auto, and you switch from a 4.10 to a 2.91 or something similar that you will get better gas mileage. you won't, the car will be too low in the rev range to make torque and will be less efficient on the freeway(kicking down constantly), not to mention how atrocious it would be around town by needing to WOT the thing all the time. In your case I would try a 3.64 and no taller (lower number). Taller the rear gear, the closer each 'speed" needs to be to be efficient and provide good acceleration in around town driving... not a strong point for an automatic, which is why they often have deeper rear gears