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Whaledriver

Overdrive choices for a 2002

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Has anyone considered an alternative installation of a universal (Gear Vendors) electric overdrive unit vs a 245 five speed for their 2002?

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Yes, but after looking at the unit I could not figure out how to mount it without having to make major modifications to the transmission tunnel to make it fit. 

It might be just as easy to use a Porsche 944 transaxle and move some of the weight to the rear axle while you are at it if you are interested in some serious fabrication.    

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In Europe they used the 3.45 diff on the Tii, but the US Tii got the 3.64. The 3.45 is about 5% taller. So you will gain top speed at the expense of a little acceleration. It's a lot cheaper than installing the 5 speed overdrive 245 trans, which is not ideal for the 3.64 stock diff since 5th is a bit too tall. That is why most people who install the 245 overdrive 5 speed also install a 3.90 diff to bring down the overdrive from 18% to about 10% in comparison to the stock set-up. I use the 245 with a 4.10 diff which brings my overdrive down to about 7% compared to a stock 2002. BMW offered the Close ratio 5 speed as an option on some of the tii cars equipped with the 3.45. This is probably a better way to go than using the 245 5 speed overdrive coupled with a 3.90 or 4.10, as it gives you better gear spacing in 1st, 2nd and 3rd gears while 5th serves as an overdrive in comparison to stock gearing..

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I use a 240/5 Speed with a GPS Speedo, much cheaper than a 245, mated to a 3.90 LSD

 

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You can also get a 3.45 gearset out of an e36 318 with a manual transmission.

Those are pretty easy to find.  It fits better into the E21 case, tho.  

 

Byron, I HAVE a 944 trans- you may as well get the Audi version, it's the same thing

just with a weaker 5th.  Right down to the bellhousing and starter mount. 

Parts cost a fraction of what the P- car parts do, tho.

 

One of these years, I'll find something to use it in.  Just...because.

 

t

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@TobyB

I actually have an e36 diff rotting in my shed, and a 4-speed driving  a 3.90LSD on my tii. I’d like to get the revs down without going to a 5-speed. Can you indicate any instructions on changing out the gearing to get the 3.45?

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Unless you're particularly adventuresome, yes:

 

Take it to a diff shop that does BMW diffs regularly.

 

It's not an easy DIY.

 

I do them for the race car, but they'd be awful noisy in a street car, usually.

 

t

 

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