Differential Upgrade 540i Automatic

[Jon K]

no - a kid @ my school has a turbo 535i with a 3.91 the RPM change is hardly noticeable. People get waaaaaaaaaaaaaaaaaaaaaaaaaay too concerned with rpm change when going to shorter (higher ratio) diff.

[Martin in Bellevue]

Yao, it is starting to sound like ya found that 540 sitting in the dead sea. The differential was hard to swap, the fuel lines were rusted. What else is corroding away on that thing?

[632 Regal]

I thought I would but with overdrive its not a big deal, if your final drive was 1:1 it wouldnt be a choice at all. Go Ebay for anything in them ratios and get what you get. the 3:64 will drive you nuts with the dead stop acceleration though, it will pull so hard youd think your gonna break something but its just the gearing making the big difference. In Germany on the Autobahn with a 3:64 your cruising speed would be in the upper RPM range, but you dont usually cruise in the 140-150 MPH range do you? If so than keep the stock unit.

I do a lot of highway driving... will I regret the change?

[Evan]

Didn't I just send you to traffic court?

I'm looking at a used 3.64LSD from an 88 735

I'm researching rebuilds... if they're possible or feasible etc.

[632 Regal]

doesnt the 735 have the small differential?

[yaofeng]

How many pounds of torque does your air gun have? Mine is about 435 ft/lbs so i don't think many bolts would be a problem.

How do you like driving the 6spd?

Thanks for reply!

Maybe my impact is inferior. But I had to loosen it first with a breaker bar before using the air ratchet.

How do I like driving the 6 speed? I can only imagine. I am not there yet. Trying to get it done before winter closes in. I have too many things going on.

[yaofeng]

Yao, it is starting to sound like ya found that 540 sitting in the dead sea. The differential was hard to swap, the fuel lines were rusted. What else is corroding away on that thing?

I suggest you crawl under your bimmer to check the condition of your fuel return line and tell us what it looks like. Or you like to bury your head in the sand?

Does it look like this?


Or like this.

[Martin in Bellevue]

There is no corrosion like that on my 535. I've been under there a few times, & all the fasteners are clean. I replaced the fuel filter last week & checked all the lines; they're rust-free. When I put the 3.64lsd in the car, it was easy to work the fasteners with hand tools. When I put Bruno's subframe inserts in, that hardware was clean too.
I suggest ya check the hardware to the gas tank straps, remember Scott H, or somebody out East, seeing those fail, allowing the tank to sag.

[yaofeng]

There is no corrosion like that on my 535. I've been under there a few times, & all the fasteners are clean. I replaced the fuel filter last week & checked all the lines; they're rust-free. When I put the 3.64lsd in the car, it was easy to work the fasteners with hand tools. When I put Bruno's subframe inserts in, that hardware was clean too.
I suggest ya check the hardware to the gas tank straps, remember Scott H, or somebody out East, seeing those fail, allowing the tank to sag.

The fasteners have to be clean. They are stainless steel. I am talking about the fuel return lines held by the SS fasteners. Not the fasteners themselves. BMW doesn't even coat the 8 mm fuel return line. It is atrocious. They didn't do it on the E30, or any models for that matter. I bet they still don't do it on the latest and greatest models. You are lucky because you live in the salt free west coast.

Now take a picture of the fuel return line and let us see it. I don't believe a 17 year old bare carbon steel tubing can be rust free even in the west coast.

[Evan]

im under my car right now.. where is the gas tank?