Removing BDR Diff

[Cashburn]

Originally Posted by ROUSHAC

Jay,

Just out of curiousity, what are the guys that are using 3.91's using for engines? Seems like it would be hard to get traction through 1st and 2nd and maybe even third with 3.91's unless you are VERY good "feathering" the throttle.

Dave

Atleast one with a 351W/450HP and the other is a Roush 402R/520HP or so. The 351 has a WC T5 (little different gear ratio) and the Roush is the TKO-600 with the .64 OD.

[Cashburn]

Originally Posted by Mark Brye

Gosh, I know how hard it is to descide on what gears to get. I have been debating between the 3:4x's and the 3:6x's for a good 3 months now. I still find myself waivering between the two gear sets. I just don't want to make
1st gear useless.
Jay,
Thanks for the tid bit on the diff about needing to drill and tap. I saw that Matrix sells a 3:73 "BDR" diff. Maybe this is already drilled/tapped. I wonder if they can drill tap any of their other gear ratio rearends?

Mark,
Our customer with a Ford Racing 392 and TKO-500 that is local went with the 3.64s even though I told him a couple times to go 3.73. We even had a miscommunication and I told him we had a 3.73 for him and he was mad. Turned out we had the 3.64 like he specified... a little while later he told me the 3.73 would have been better

[6t8stang]

I unfortuntately cannot comment too much *yet* on how my 351W/450HP with 3.91's performs as I'm still being gentle during breakin (and it's friggin cold now so seat time is few and far between). I don't believe the gearing was changed on my WC T5 (2.95 1.94 1.34 1.00 .63) - Jay?. First impressions while keeping it under 4k RPMs isn't as bad in 1st gear as I thought...we'll see when I start to drop the hammer a bit....

[Whiplash]

Metrix will be sending Jay my 3.73 LSD e-36 next week. It was about $1300. I did see some .46 on E-bay a while back for around $400. I'm sure once it all gets put together we'll be able to chime in a little better.

[madmaxx]

I had 3.91 with a tremec 3550 and for what it is worth first gear was STEEP. It was a real challenge for me to hit second before the rev limter, 2nd gear was heavenly. I think 3.73 may be the sweet spot.

[Cashburn]

The most important thing to consider when discussing rear end ratios is the gearing of your transmission. For this reason keep in mind:

Tremec WC T-5 2.95 1.94 1.34 1.00 0.63
Tremec TKO-500 3.27 1.97 1.34 1.00 0.68
Tremec TKO-600C 2.87 1.89 1.28 1.00 0.82
Tremec TKO-600W 2.87 1.89 1.28 1.00 0.64
Tremec T-56 2.97 2.07 1.43 1.00 0.8 0.62

[SkipB]

Whiplash,

Is that Metrix or Metric Mechanics?

SkipB

[Whiplash]

Customer Service
Metrix Motorsport
(818) 545-0866
metrix_info@sbcglobal.net

Link to the 3.73 LSD:

http://estore.websitepros.com/139711...103cb27e798804


Hope that helps. They have been a little slow with getting the part to Jay though (broken promises, never returned e-mail). Just a heads up.

-Sean

[Mark Brye]

Thanks for the heads up Sean. I just talked to them on the phone and they indicated that the diffs are built to order. They told me it would be about 10 days to build up a diff for me and about 3 days for delivery from CA to Washington State.
Sounds like he is willing to Tap the diff for me with the correct 14mm, 2.0 bolt. He was going to double check that was the right size for my car as he thought it might be a different size and wanted to know for future Backdraft diff orders.

[tamanaco]

Originally Posted by Cashburn

Mark,
Make sure you drill and tap the diff for the front mount. Stock BMW diff. will not be setup this way.

FYI...Just tapped my,new to me, 3.91 diff with a 14 mm X 2.0 pitch thread on the front mount on BDR car #260...this is what it had leaving the factory?

Any one want to buy a 3.1 or .15 ratio open E36 diff with a BDR tap sized front mount?