best diff for an m52 swap
 

I was wondering what the best diff would be for an 328/m52 swap. I drive about half highway, and half city. Ill be using my getrag trasmission to save some money. I just don't want to be at 4000 rpm's at 80mph.

Which would would be best? i was thinking 2.93 or 3.25.

Thanks in advance,
John

And yes, I searched!

I have a 3.54. It revs pretty high on the highway.
I want to say at 80 it revs almost 4K.

Both needles put to 12 o'clock.

there are a few different ratios available if you convert to the e30 medium case differential. the ti small case may have choices, but all I have seen listed are the 3.45 for the manual and something like 4.10 in the automatic. there is a supplier of differentials: diffsonline.com the website will show various ratios that are available. I have a 3.23 medium case, which was the same as the 95 m3-----at 70mph I turn 3000 rpm-----80 is about 3450. your engine swap will give you low end power for the numerically lower diff ratio, but the lower number will slightly affect your initial acceleration from a stop, so you want a balance between highway rpm's and strong acceleration to take advantage of the increased power.

I have a 3.45 lsd listed for sale. I did an automatic to manual swap and it worked pretty well for me.

Ok. So it sounds like 3.25 would give me that happy medium. Thanks for the avice guys. Now I just have to find an m52.....

Thanks,
John

I would do more research if I were you... I bet some here at 318ti.org would chatter and be glad at making fun of other people's tuners... and lead them in the wrong direction because it was hilarious! happened before... I don't know anybody here by all means... but some of people's advice is good I will say that... which is why I will support this site...

Lbcnu: I have never seen anyone on this site give incorrect advice intentionally because it would be funny. Maybe you have been burned on other forums but that is not how we operate over here.

Diff ratio selection is a matter of preference and purpose. Anything between 2:93 and 3:45 should work for most applications. I am using a 3:08 on my swaps. I like a useable 1st gear, being able to get to 60 in 2nd, and the mpg at highway speed.

I agree with Bimmerbum's response, we tend to be respectful of other Ti owner's questions and respond in kind. Enjoy the site and don't hesitate to participate. Enjoy the ride!

Not really brother (assuming). Everyone on this site has been more than helpful, responsive and friendly. Its a lot more laid back than bimmerforums, but just as informative and specific to ti's(obviously). Its why i still frequent this site. This is the only forum i have ever belonged to where i have never been "flamed" or anything of the sort for a simple questions.


John. Now, lets squash that. Somehow we got off topic.

Now, if anyone has any specifics. I want to cruise at 80 in 5th, and want to be at 3000-3200 rpms.

3:08 will put you around 3300-3400 at 80. If your only concern is highway cruising rpm (which I am guessing it is not as you have a swapped ti) then you will want to go with a 2:93 to achieve the 3000-3200 goal you are after.

Ok guys, it's all good.

And thank you guys for pointing out the kind attributes many have exemplified on here. And I agree... Other forums are not like this one... Which is nice to see and experience... The useful knowledge that many have posted is good to look at, based on others experience... I would hate to see someone not investigate what their criteria demands in relation to mpg, rpm, torque, etc... and take someone's word for it and not get what they needed... I spoke too soon...

and some vagabonds at other forums have simply put people through it... unnecessary roughness... Which hasn't happened here... phew!

That's sweet Bmorekirby...

Good Points BimmerBum... (i bought some oil filters from you) good follow through by the way...too!

~Squashed~ "happily"

Thank you!

I decided on 3.25 for my S52 swap and taller tires for the street and shorter for the track. I was able to get a Euro LSD which is much stronger, 4 disk, custom setup for me at a reasonable cost. I stayed with the smaller case to save weight so adding a dual ear cover and making a custom mount for the chassis for it.

I had to go 3.25 to get that LSD but it worked out as a good overall ratio for street and track with shorter track wheels and tires.

If cannot get the exact ratio you want you can do use taller or shorter tires to dial it in, to a degree at least.

If not for the Euro LSD I would of done a medium case diff swap, probably a good idea with any larger engine swap to do so.

I'm getting ready to do my manual swap but before I start anything I need to get another diff. I have pretty much the same question and reading the posts gave me a better understanding.

I would like to find a diff I can swap in without having to do any conversion or modifications. Would a Z3M 3.25 one ear diff fit in the ti?

Im not going to be tracking the car or anything but i do plan on an engine swap sometime around feb. Looking at the M52 as well. I do a good bit of both highway and city driving so i want something that will be a happy medium as stated previously and it sounds like a 3.25 LSD will be my best bet. Am i correct?

My other question is can you fine gents (and possibly lasses) point me in some direction as to where i can get some ti specific info for the auto to manual swap..?