About a year ago I decided to regear my '74 3.0CS it has a 4.10 LSD I found on eBay a 3.07 (maybe not .07 but whatever). The ebay was a big lie, not the claimed ratio not the LSD, nothing right - but eBay got my money back!! Due to that deal I almost sold the car, last week we took an hour and a half ride to look at a Mark II Jag, he was thinking of a trade. After driving his Jag and driving the BMW the 1.5 hours each way I want to keep mt BMW. So, what I've got is a Korman Stage 2 engine with a 4 speed manual and a 4.10 rear. it's real fun to drive but I'm always looking for 5th gear and there isn't one. And cruising around with my wife, It's just kind of raving too high. So, from people who know, what would be the best gear ratio to make it a little less rally car, and a little more regular around town car~ Also where to get one
Looking for gearing opinions
- Thread starter Rod Cole
- Start date
Your 4.10 diff must have come from 69-72 Neue Klasse 2000 sedan as they had a sideloader. I have that in my NK and it is intolerable without a five speed. The 3.07 from an e24 will have very long legs, a 3.25 from a CSi is perfect with a four speed, a 3.45 from an e3 is OK but still turning some RPMs at freeway speeds and a 3.64 from any US e9 will need a five speed tranny. Hope this helps.
There are several diffs listed under the e9coupe parts for sale section for a variety of prices. You may also find some at wrecking yards or FB marketplace near you.
I can't imagine what a 4.1 diff would be like.. Even 3.64 is too short...
3.07 works OK with a 265 trans and a big engine, but as Chris says, it has VERY long legs. My 635 has that setup and you cannot even think about 5th gear below about 75-80, so sort of the opposite of the 4.1
3.07 works OK with a 265 trans and a big engine, but as Chris says, it has VERY long legs. My 635 has that setup and you cannot even think about 5th gear below about 75-80, so sort of the opposite of the 4.1
day66
Well-Known Member
My own CSi has the 3.25 LSD and I find it perfect for the driving I do. If you are likely to doing many miles cruising above 80-85 then maybe a fifth gear would be a benefit- but in the UK the opportunities and chances of doing more than 70 for more than a few miles are now very limited..
Around town (city car) a 3.45 is nice, a road car for distance or fast driving or relaxed driving a 3.25 is good and even better with your performance engine.
3.25 sounds best for you.
The 3.07 gets mated to a 5 speed close ratio gear box.
I believe I have 3.25 open diffs on the shelf available.
3.25 sounds best for you.
The 3.07 gets mated to a 5 speed close ratio gear box.
I believe I have 3.25 open diffs on the shelf available.
The 3.25 is sounding very right, so my question is "can the 3.25 have my 4.10 posi unit installed in it"? I put a "Locker" in my '54 Chevy 3/4 ton which involved re-shimming the ring gear using the lead marking compound & a dial gauge, so I can do that - but is it possible?
There are a lot of combinations and they don’t necessarily go together.
3 different LSD units in total.
There are 2 different 3.25 diffs. Late and early. First has 8 bolts and second has 10.
Early LSD units are made different from later ones. My diff shop won’t rebuild them.
Your 4.10 is a 8 bolt ring gear version.
If you want to move it to a open 3.25 diff you will need the early diff with the bolt on side/output flanges.
3 different LSD units in total.
There are 2 different 3.25 diffs. Late and early. First has 8 bolts and second has 10.
Early LSD units are made different from later ones. My diff shop won’t rebuild them.
Your 4.10 is a 8 bolt ring gear version.
If you want to move it to a open 3.25 diff you will need the early diff with the bolt on side/output flanges.
Rod, since you are in Maine, you might want to check with diffsonline.com. VSR in NH uses them, they are in Wilmington, MA ... give them a call at 800-219-0485 ... they primarily do BMW diffs.
Given a choice would you go with a 5 speed with a 4.10 or a 3.25 with a 4 speed?
Hands down 3.25, a 4.10 is way too low. My NK with 4.10 and five speed is 3,000 rpm just to get it to 65mph.
here are the basic speeds with the o/d 5 speed ... you can ignore the 5th gear and see what 4th gear does for you. the o/d 5 speed has the same gears as the 4 speed for 1 thru 4. ignore the 3.46 notation - i must have had too much wine that night. doesn't really make a difference.
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we check ours on the grass at the local soccer field- no mistakes that way..
Jack your car up by the diff and take a serious look and a pic.
I believe the 2800 had a load dependent LSD....
Jack your car up by the diff and take a serious look and a pic.
I believe the 2800 had a load dependent LSD....
My 4.1 is for sure LSD, and I haven't gotten anywhere looking for a 3.25. I did email diff online, got no reply & just been busy working around the yard, garden, house for spring clean-up. I might think about an open differential, but here in Maine it's very to find snow off season and a posi rear in snow is handy~
Still looking~
Still looking~