E30 rear diff swap

[Blckevo8]

Hello!! First time to post a something. Just trying to ask about a 3.25 LSD that I found and about to buy, I have a 1986 325e, manual, sedan. The LSD is coming from a 1984 e23( its either from a 733 or. 735 ). Would this fit or is it too big? The seller said it would fit, just swap the cover and the flanges.

[MR 325]

Yes it will work. My 3.46 LSD is from an E23. Swap the E30's output flanges and rear cover!

[Blckevo8]

rear diff

Much appreciated MR 325!!!

[lost in DC]

I hope it's OK to tack on my question to this thread.

I'm looking at possibly purchasing a 318is. I get the impression that they are not factory-equipped with an LSD, unless the LSD option was specifically added. If that's true, what LSD's should I look for if I want to add one after the purchase. Thanks for your advice.

[MR 325]

I hope it's OK to tack on my question to this thread.

I'm looking at possibly purchasing a 318is. I get the impression that they are not factory-equipped with an LSD, unless the LSD option was specifically added. If that's true, what LSD's should I look for if I want to add one after the purchase. Thanks for your advice.

You're right. The 318iS only had a LSD on optioned cars. You can look for the 318iS small case 4.10 LSD which is a bit on the weak side and getting harder to find OR you can look for a medium case 4.10 LSD from an E30 M3, automatic 325iS, or optioned 325i/ic. It's a direct swap.

[lost in DC]

Thanks MR 325!

[Wanganstyle]

Hello!! First time to post a something. Just trying to ask about a 3.25 LSD that I found and about to buy, I have a 1986 325e, manual, sedan. The LSD is coming from a 1984 e23( its either from a 733 or. 735 ). Would this fit or is it too big? The seller said it would fit, just swap the cover and the flanges.

Make sure its not a 1982/1983- the EARLY e28/e24 188mm differentials have a WEIRD rear cover pattern that is NOT COMPATIBLE with e30 differential covers-

If you go to the dealer ship and buy a $2 e30 paper gasket for a 188mm (325i 1990) you can bring the gasket to match up with the old ass E23/e24/e28 diff.

this way you can make sure you don't end up with a useless iron lump of leaky smellyness.

[lost in DC]

What does a person look for when buying a used diff with LSD? Thanks.

[jlevie]

There are a couple of checks you can do on a used differential. One is to see how much rotational free play there is in the input shaft. The other is to see what torque is required to turn one output shaft while the other is held against rotation. And the best was to do that is to bolt a strap across the output flange that has a nut welded to it. If the clutch plates are in good condition it should take 65ft-lb of torque.

[lost in DC]

Thanks Jim. I think I follow what you said. If trying to buy one used over the internet, would it be kind of a crap shoot as to whether it's a good one or not? Or are there specific things you could ask the seller to demonstrate, perhaps in pictures? Thanks again!

[jlevie]

You could ask for the torque check to assess the condition of the clutches. Checking rotational free play of the input shaft is somewhat subjective.

[lost in DC]

Thanks again, Jim.

[gnarkilla1988]

i also have a question related to this. i dont know what year it is exactly. but there is an '' early model'' 325is at the local junk yard. will this work in my 86es and is it a direct swap or what would i need to do. i have heard that a diff is one of the best upgrades for an es to give it some more pep. thanks guys

[jlevie]

i also have a question related to this. i dont know what year it is exactly. but there is an '' early model'' 325is at the local junk yard. will this work in my 86es and is it a direct swap or what would i need to do. i have heard that a diff is one of the best upgrades for an es to give it some more pep. thanks guys

That differential would be a direct swap. An 86 325es with a manual transmission would have a 2.93 differential. The 325is with a manual transmission would have a 3.73 differential. The change in ratio will improve acceleration at the expense of higher engine speed. At 60mph the engine will be running about 600rpm faster.

[gnarkilla1988]

ok thanks for the help. i knew the ratio would be alot differant. and i have herd that the 3.25 may be a better choice,but living in wyoming and not having alot of car funds right now,i figure it would be a good experiment. i had big plans to build a 2.7i, 1.3 motronic,323 head,272 cams,MS,blah blah blah,but i have decided to just do the 3.73 diff,ebay headers (came with the purchase of the car,why not throw em on right?) and a jimC. then save for a 325i and start from there. maybe i will turn the es i have into a track rat,or do a s5x swap some day with it. i was beyond an e30 newb when i bought the car,and at first was sad it was the eta,but i love my little car. i just dont want to dump alot of money into right now. id rather start with an "i".