Advice for higher gearing

[buzzboy]

My compact drivetrain is currently S52, ZF and e30 4.10 LSD. I'm looking to go to a higher ratio rear end. The 4.10 is useless on the highway, turning 4000 at 80mph and drinking gas quickly. Also there is a bit of a rear end whine. I don't know how bad that is, but I know it can't be a good thing.

I would like to go to a ratio in the 3.00-3.50 range and I would like to maintain my LSD. From what it looks like my best option is to find a Z3 diff. The charts I keep finding online don't show many good LSD ratios for the mid-case e30. Is this correct? So far this is my list of cars to look for in junkyards. Anything else? Would it be hard to find a quality diff in that age range on the e30 or should I just start looking for z3 equipment?

So my donor choices would be:
325es 3.23 post 1986
325is 3.46 pre 1986
Z3 2.8 3.15
Z3 ?.? 3.46

[1996 328ti]

I can tell you my M52 revs pretty high with a 3.46.

[buzzboy]

Upon some research, I was mistaken in calling mine a 4.10, it's actually a 3.73. That's scary. Playing with a gear ratio calculator I'd like to go for a 3.23, 3.15 or similar in LSD.

[1996 328ti]

Originally Posted by buzzboy

Upon some research, I was mistaken in calling mine a 4.10, it's actually a 3.73. That's scary. Playing with a gear ratio calculator I'd like to go for a 3.23, 3.15 or similar in LSD.

Those are saner ratios. My 3.46 is OK on track, but not on the highway. Especially with a loud exhaust.

[Bluebimma]

Ive run 4.10 for a couple years, hadnt noticed a difference in mpg. Just get on craigslist or some local forums and look for an open 3.25, 3.46, or 2.93. 2.93-3.25 are normal e36 and z3 ratios that are harder to come by on the cheap. An open 3.25 goes for about 75$ and you just move the LS over and swap ring gears.

[wolferj-RIP]

Originally Posted by buzzboy

My compact drivetrain is currently S52, ZF and e30 4.10 LSD. I'm looking to go to a higher ratio rear end. The 4.10 is useless on the highway, turning 4000 at 80mph and drinking gas quickly. Also there is a bit of a rear end whine. I don't know how bad that is, but I know it can't be a good thing.

I would like to go to a ratio in the 3.00-3.50 range and I would like to maintain my LSD. From what it looks like my best option is to find a Z3 diff. The charts I keep finding online don't show many good LSD ratios for the mid-case e30. Is this correct? So far this is my list of cars to look for in junkyards. Anything else? Would it be hard to find a quality diff in that age range on the e30 or should I just start looking for z3 equipment?

So my donor choices would be:
325es 3.23 post 1986
325is 3.46 pre 1986
Z3 2.8 3.15
Z3 ?.? 3.46

The Z3 6 cyl automatics are the one's that come with the 3.46. I've been running the 3.15 z3 diff in for a year and it's decent. I actually would like a slightly higher ratio (3.25 or 3.46) as I do more track with the M50 swapped ti.

[buzzboy]

Is yours a torsen or a clutch type? I'm more of a "spirited highway" driving kinda guy but I put upwards of 10,000 miles on a car with a lot of open highway and interstate driving making up a lot of those miles.

[wolferj-RIP]

Torsen diff from a Z3. I suspect that you would be happy with the 3.15 ratio. You could even run a 2.93 e30 diff if you want a clutch type unit..

[buzzboy]

I don't mind what type of LSD really, but I like the concept of torsen with them not having clutches to wear out if I'm getting a used unit.

I figure that currently I've got a first gear of 15.6 which will pull me along pretty well. 3.15 and 2.93 gears would give me a first gear ratio of 13.23 and 12.3 respectively. I've driven cars with gearing as high as 9.4, which is way too high, but I think I could work with either 12.3 or 13.2. This would leave me open for a few choices of rear gears to pick from.

[samdemange]

maybe help u

[M-technik-3]

US market never got a 3.46 nor a 3.64 or a 3.91 LSD they were a 3.73 or a 4.10 for i cars. E28's got a 3.25 lsd which many E30 guys swap in when they do 24V swaps. Early e cars have the 2.79 which make them dogs but good on gas but the 2.93 gave it best of both.

Turbo E30 guys use 2.79 or 2.93 for top end. I am building basically the same car I am using 3.15 lsd.