Differentials

[dapper83]

I have heard that changing the rear diff improves acceleration significantly does anyone have a recommendation as to what ratio to put 3.__ where to get it, how much it would cost and who makes it? Thanks in advance
This is for a 95 325 conv

[Dave at Pelican Parts]

You use the rear diff from the automatic transmission cars in a car with a manual transmission. This gives you "shorter" gears and therefore more thrust.

The downside is that you have to run higher RPMs on the freeway. Your fuel mileage for freeway driving will go down because of that as well. And, of course, you will have to change gears more frequently.

--DD

[dapper83]

Thanks for the reply do you know how much they cost i have seen as low as 500 and as high as 2500 why such a price difference.
John

[Dave at Pelican Parts]

No idea.

--DD

[Jared at Pelican Parts]

I have seen differentials go for $300-400 on ebay. It's really just a matter of if you buy one new or used. At present, Pelican does not carry diffs. I dont know where you would go to purchase one either. I would imagine that the price is dependent on whethwer or not the diff is limited slip and any custom ratio.

One question, do you have a manual or auto? This will affect the ratio you put in the car.

Like Dave syas, if you change the ratio, say from a 3.73 to a 4.10, you will get a lot more acceleration, however you will find that at freeway speed, the car will rev higher than with the stock unit. This will also affect the fuel mileage of the car as well.

[dapper83]

I have a manual and i beleive a 3:15 i was thinking of a 3:46 is that too much not enough? Would a used diff be a risky investment? or would it be best to save up for a new one? Thanks for the replys
John-

[Roald]

i'd say get one used and once you have it open it, inspect pinion and ring gear teeth for damage and change bearings and seals. then swap the diffs. this way you will have a rebuilt unit for a fraction of cost of a new one.

[Jared at Pelican Parts]

I agree, it's not a bad idea to change the bearings and seals. I havent done it on a BMW diff yet, (never had to!), but i imagine it wouldnt be too hard.