3.62 gear ratio Limited-Slip Differential rebuild into 01 740i Sport Shorty

[Rhein Amacher]

As mentioned on previous posts of mine, I have been trying to add a limited slip differential to my 01 sport while minimizing the cost. And now I finally have succeeded!

Parts (all from local junkyards)

✷ 3.15 Open Differential 210mm large carrier from 1995 e38 740iL - $125
✷ 3.62 Limited Slip Differential 210mm large carrier from 2004 e46 M3 - $600
✷ 210mm differential rebuild kit - $150
✷ LiquiMoly Fully Synthetic Limited Slip Differential Fluid 75W140 service kit - $75

Total spent without labor: $950


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[Rhein Amacher]

Now with pictures of the finished product! Brendan McIntire, owner at Speed Garageworks, is the brainchild of the new custom-built differential. I sourced together all the parts and Brendan did the actual rebuilding.

The new, rebuilt differential in my 01 740i Sport, will feature a shorter gear 3.62 Limited Slip Differential with a 210mm spool from a donor e46 M3 (NOT 215mm carrier that comes standard OEM on the 96-01 e38s) and installed in the 95 e38 3.15 open differential carrier housing. Since this custom limited slip differential IS a direct bolt in to the E38 facelift models produced from 09/1998 to 07/2001, the only difference is that the nose is 19mm longer than the 215mm carrier housing in the e38s produced after 03/1996 and later. That means the rear CV joint on the driveshaft is compressed more than design intended. However, from what I've been researching, it does not have any negative effect.




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[Sabreslight]

Congrats! Why did you go with the 3.62 instead of the 3.15?

[Rhein Amacher]

Congrats! Why did you go with the 3.62 instead of the 3.15?

I wanted a shorter gear and maximize the amount of torque I could get off the line. Remember, the E38 did not come from the factory with a LSD, at best, the facelift 99-01 sport models came with a 3.15 gear ratio open differential, as well as the M60 V8 models produced before 03/1996. Interestingly, Dinan came out with a LSD for the E38 chassis with the M62 engine in two different ratios: 3.15 and the more rarer 3.45 gear ratio. Now what people might not know is Dinan released a even shorter gear LSD for the M60 engine and was only available for one year in 1995. The M60 engines were offered the upgrade to a 3.73 LSD.


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[740il97g]

I wanted a shorter gear and maximize the amount of torque I could get off the line. Remember, of course the e38 didn’t come from the factory with a LSD, at best the 99-01 sport models came with a 3.15 open differential. Now Dinan came out with a limited slip for the e38 in a 3.15 and even rarer 3.45 gear ratio. So I felt the need to one up Dinan.






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Nice I want to do this to the 750 if I keep it. Post a video or let us know how it drives.. Especially on the highway.

[Sabreslight]

I wanted a shorter gear and maximize the amount of torque I could get off the line. Remember, of course the e38 didn’t come from the factory with a LSD, at best the 99-01 sport models came with a 3.15 open differential. Now Dinan came out with a limited slip for the e38 in a 3.15 and even rarer 3.45 gear ratio. So I felt the need to one up Dinan.


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Interesting, definitely post up how it handles the highway. I'll keep my 3.15 lol I still ha e to finish mine.

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[COOPERDB]

`


Ryan - great job obtaining the necessary components -

I know that this has been a mental project of yours

for quite a period of time -

Going with the 3.62's is a smart move -

I will be very interested as to what your RPM readings are

for 55 / 65 / 75 MPH -

Also what size tyres you are running at these freeway speeds -

At the very least in your Metropolitan area your 740i will be

one of a kind - if not the rest of the...

Looking forward to your updates -


Thank-You
D.B.


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[rslifkin]

Assuming 27" tall tires and 70 mph, a 2.93 diff gives 2050 rpm, 3.15 is 2200 rpm and 3.62 is 2520 rpm.

[racer2086]

Wow nice post. Please keep us updated. In for RPM figures. rslifkin is probably pretty close, although I'm pretty sure my 98 is higher than 2k rpm at 70 mph... Maybe I just forget it's been so long.

[rslifkin]

The figures I gave are calculated, so it's possible the tach in a car doesn't read 100% accurately or something. And those numbers also assume a working lockup clutch in the torque converter. The number for 3.15s does match pretty well with what my sport shows on the dash, FWIW.

[racer2086]

Yeah, you're probably right. I still haven't got my car back, so I haven't driven it in 4 months. I was just going off rough memory. You're probably on the money.

[Sabreslight]

Just bought my lsd unit, now to find another 95 rear end.

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[COOPERDB]

`

Assuming 27" tall tires and 70 mph, a 2.93 diff gives 2050 rpm, 3.15 is 2200 rpm and 3.62 is 2520 rpm.

Appreciated -


Thank-You
D.B.


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[Rhein Amacher]

Will do! Keep in mind though since you have a 750, the LSD project might or might not work if you choose the e46 M3 as the donor project car. Check out the response I attached from a
LSD guru on E38 Empire on Facebook:

[Rhein Amacher]

Just bought my lsd unit, now to find another 95 rear end.

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Hey Sabre, what LSD unit did you end up picking up? Check http://www.autowrecking.com/ and or http://www.car-part.com/

[Sabreslight]

Hey Sabre, what LSD unit did you end up picking up? Check http://www.autowrecking.com/ and or http://www.car-part.com/

I picked up a m variable unit on ebay, and there is a 95 local that I'm going to get the diff from on Thursday

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[absolutezero273]

Will do! Keep in mind though since you have a 750, the LSD project might or might not work if you choose the e46 M3 as the donor project car. Check out the response I attached from a
LSD guru on E38 Empire on Facebook:

Thanks Ramacher. Is there hope for me? if RealOEM is accurate my 01 750 has a 94mm/27mm output shaft while the e46 M3 has a 27mm/38mm output shaft. So we are concerned about the shaft length, right?

[Rhein Amacher]

Thanks Ramacher. Is there hope for me? if RealOEM is accurate my 01 750 has a 94mm/27mm output shaft while the e46 M3 has a 27mm/38mm output shaft. So we are concerned about the shaft length, right?

Well you mixed the numbers up, but no worries you should be fine. The e46 M3 uses 94M10s and your 2001 e38 750iL uses 94M10s as well. Don't look at the second number of the output shaft. Them you look at the first number of the Torx Screw with ribs and that number is M10X43 ZNS3. Again, forget about the last digits. You have 94M10 if you car is built after 06/2000.

[absolutezero273]

Well you mixed the numbers up, but no worries you should be fine. The e46 M3 uses 94M10s and your 2001 e38 750iL uses 94M10s as well. Don't look at the second number of the output shaft. Them you look at the first number of the Torx Screw with ribs and that number is M10X43 ZNS3. Again, forget about the last digits. You have 94M10 if you car is built after 06/2000.

That's what I get for trying to do 2 things at once!

I was concerned there was another aspect of the axle specs that was a requirement and you confirmed it with the 'Torx screw - M10x43 ZNS3' deets. (And I typed it right this time) Thanks!

[COOPERDB]

`


Ryan -

Any updates on the new gears

or are they just too much fun to

stop and post -

I hope the assembly and install

was smooth -

Please keep this thread updated -


Thank-You
D.B.


.

[Rhein Amacher]

Hey D.B.!

After an accident back in the spring done by driver error, I finally got to install the custom-made 3.62 LSD in my whip, as well as install UUC Motorwerks front and rear sway bars. Now to the alignment shop! And this is my 1,000 post! Whoo-hoo!

[Rhein Amacher]

Hey D.B.!

After an accident back in the spring done by driver error, I finally got to install the custom-made 3.62 LSD in my whip, as well as install UUC Motorwerks front and rear sway bars. Now to the alignment shop! And this is my 1,000 post! Whoo-hoo!

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[Rhein Amacher]

Hey DB,

After two miserable years, family issues and COVID, I finally got the custom 3.62 M-Variable LSD installed in my 01 Shorty. Installing the LSD was easy plug n’ play, even a caveman could install this part with the right tools, with the only nuisance being having to work around my aftermarket Remus Sports Exhaust (stock exhaust from factory should have no issues whatsoever). What are some pics you wanted to see on the odometer again? I noticeably have seen my gas MPG gone down a little bit, but the pros outweigh the cons of course in this mod! Any questions feel free to reply to this thread…

[joshhas99probs]

Awesome to have anoother option for LSD. Definitely on my short list.

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[joshhas99probs]

Branden is a wizard when it comes to this shit. I have sold him countless diffs over the years!

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