S50 E30 swap - Differential Question

[USSR2K]

I work part time at a local salvage yard. I came across a 1992 convertible with a 4.10 slip differential. I am willing to trade this for something that is quite and fits my 1986 325 E

[richardb]

So I don't get bashed for starting a new thread...

I have a nvm50 with g240 trans, and small case 4.10lsd HORRIBLE on the highway. I drive highway 90% of the time. Will be doing a turbo setup next spring... I am thinking 3.25 lsd... yes? I would like to be between 3000 and 3300 rpms going 80. I travel 80 on the highway in good conditions, 70 in light traffic and probably 60 in heavy traffic on I95.

SO any advice for the best option?

[Uber E30]

3.25 or 3.46 for turbo

[e30polak]

3.25 or 3.46 for turbo

Or 2.93. It depends on the size of the turbo. If the OP is going for a bigger turbo then I'd say 3.25 or 3.46. If it's a small turbo that will spool quick, then you will want a longer power band before the turbo chokes, i.e 2.93

[Wh33lhop]

I'm also thinking of going a little longer when I get the car back together (M50NV), thinking maybe a 3.46 for the G260 in there. I like the stock short gearing for dicking around, but without a 6th gear on the highway 3500rpm at 80 gets kind of old, and I'd like first to be a bit longer, maybe reach 37-38mph instead of 30 flat.

Has anyone run an M50 and a G260 with a 3.46 or a 3.25? I don't want stupid high eta gearing or anything, but just curious to read people's impressions.

[FredK]

I have a pretty loud exhaust, a ZF320, slightly undersized tires, and a 3.46. I drove to NJ and back with no radio a couple weeks ago. It wasn't that bad.

[5KWattson]

that gearing calculator, i just scrolled over it but how would i fig a 4:10 with a Gatrag 260 an a m50tu rpm at 80 mph

[D-rock]

I had the 2.93 in my car and the gears were sooooo long i really liked it. On the 3.25 i was in 5th doing 75 at 4k and couldnt get anymore out of the car so i really dont know.. :/

[5KWattson]

damn i have a feelin its guna suck ass for freeway and i drive like 13 miles to work every day...FML...oh the reason i say im have a feelin is with my m20 my cluster never worked so i didnt even know the rpm difference between the 3:73 and the 4:10, but the M50 is goin in really soon so i need to get another one

[D-rock]

I feel like the 2.93 is the way to go! there is not that much of a difference. Between 3.25,3.46

[e30polak]

I feel like the 2.93 is the way to go! there is not that much of a difference. Between 3.25,3.46

Wrong! :hitler:

The 3.46 is definitely a nice jump from a 3.25. The moment I drove it at first, it felt like I got another 20lbs of torque throughout the powerband! :-D

I want to try out a 2.93, since it would make 1st and 2nd longer.

[Wh33lhop]

that gearing calculator, i just scrolled over it but how would i fig a 4:10 with a Gatrag 260 an a m50tu rpm at 80 mph

With a 4.10 and a G260 you'll be at about 3700rpm at an indicated 80mph.

I had the 2.93 in my car and the gears were sooooo long i really liked it. On the 3.25 i was in 5th doing 75 at 4k and couldnt get anymore out of the car so i really dont know.. :/

Sorry but even with a 1:1 5th gear and a 3.25 you're not turning over 4000rpm at 75mph. A ZF/G250 with a 1:1 and a 3.25 will be about the same as a G260 and a 4.10: 80mph at about 3700rpm. If you're doing 4k at 75mph and you're running an E36 gearbox, you've got a 3.73.

I feel like the 2.93 is the way to go! there is not that much of a difference. Between 3.25,3.46

The difference between a 3.46 and a 3.25 is about 65% that of the difference between a 3.25 and a 2.93. So, is it as noticeable as the change from 2.93 to 3.25? Not quite, but it'll be in the same ballpark.

[D-rock]

Now what will give you a bit longer gears a 3.25 or 3.46. I feel like I might go back to the 2.93. Of the line it was a bit slow. But on the high way it was very nice!

[e30polak]

Sorry but even with a 1:1 5th gear and a 3.25 you're not turning over 4000rpm at 75mph. A ZF/G250 with a 1:1 and a 3.25 will be about the same as a G260 and a 4.10: 80mph at about 3700rpm. If you're doing 4k at 75mph and you're running an E36 gearbox, you've got a 3.73.

Sounds about right. A 3.73 with a ZF cranks 80 at something like 4500. I used to run 75 @ 3100 with 215/45/17 which were a little over-sized, when I had the 3.25.

[Uber E30]

With a 4.10 and a G260 you'll be at about 3700rpm at an indicated 80mph.



Sorry but even with a 1:1 5th gear and a 3.25 you're not turning over 4000rpm at 75mph. A ZF/G250 with a 1:1 and a 3.25 will be about the same as a G260 and a 4.10: 80mph at about 3700rpm. If you're doing 4k at 75mph and you're running an E36 gearbox, you've got a 3.73.



The difference between a 3.46 and a 3.25 is about 65% that of the difference between a 3.25 and a 2.93. So, is it as noticeable as the change from 2.93 to 3.25? Not quite, but it'll be in the same ballpark.

Uh, sorry but you're wrong.


4.10 on a g260


3.25 on a ZF