Anybody change the gears in the rear end

harley · #1 (**permalink**) 03-26-2004, 07:01 PM

I have about 500 miles on the BDR and still working through a few nits here and there. I have a question - I have a 351W with an AOD and in O/D the engine only turns about 1200rpm at 50mph. I know it is an automatic - please stop laughing - I am concerned about performance --

I am starting to think about moving to the 3.43 or 3.95 - anyone have any experience with what the difference in performance would be - i am not certain I need it - the tires will light up if i just slap the throttle at a dead stop - but it lugs a bit in O/D at 50 --

Thanks for any info

jim

Tim Brewer · #2 (**permalink**) 03-26-2004, 09:09 PM

What's up Harley! I'm not 100% sure about an automatic, but anything taller than a 3.50 is too tall in a light weight car such as a Cobra. I had a 3.50 and thought it was too tall, then changed to a 3.70 and like it much beter. Annother thing to consider with your car is availibility of gears, isn't your diff. a BMW?

Good Luck, Tim

CSCHWER · #3 (**permalink**) 03-28-2004, 08:17 AM

Just leave your tranny in "D" OD (5th) gear is for >70MPH crusing. I put mine in 5th once just to see if it worked.
I have a 3.91 limited slip that I have never installed because I'm starting to like the 3.10/T5 combo. I think installing the 3.91 would require me to change the transmission also to get a useable 1st gear

Chet

Ron61 · #4 (**permalink**) 03-28-2004, 09:12 AM

Chet,

I have 3:27 gears in mine and the 1st gear is still useless. Even 2nd isn't much good on street tires. The 5th is like yours, great for freeway crusing. Anything in the 3:50 and lower ratios and I would have to start out in 3rd gear. I have 3:91s in a heavier car with posi-trac and the street tires are still useless in 1st gear unless I just get it rolling real easy and ease into the throttle.

Ron

tfarhood · #5 (**permalink**) 04-05-2004, 06:39 PM

I have the 3.45 rear end with a standard T5 (3.35 first gear and .68 OD). I have a 302 built with the Edelbrock Performer RPM package to get power to the gears. 1st gear is still pretty good. I get about 28 mph before it is reving too high, normal shift at about 20 mph. 65 mph is at 2000 rpm in OD. 2nd and 3rd gears are a blast. All in all it is not a bad package. A 2.95 1st gear from a T5Z would be a little better.
P.S. The BDR side pipes sound better than most others!

trularin · #6 (**permalink**) 04-06-2004, 05:09 AM

It is not a requirement to use the OD. You can use the D position on the trans and it will drive fine. Shift into OD when you are out on the freeway and "moving along".

Ron is right, much more than 3.5 and you are not going to be able to start out without at least barking the tires.

klayfish · #7 (**permalink**) 04-06-2004, 05:56 AM

Harley,
I also have a 351W in my car. I have a T5 trans, so they are somewhat different, but hopefully my info will help some. I have the 3.73 gears in my car. Yes, I can smoke first gear very easily, espcially with the ratio of the T5 first gear. However, I don't find it as difficult as others say to pull away smoothly from a stop. No, I can't make it silkly smooth, but at the same time, I can easily do it without spinning the tires. First winds out quickly, but I don't mind. If I'm really concerned about traction, I start in second (though I almost never do this). When I'm cruising on the highway, I turn about 2500 rpm at 75 mph. I love having the 3.73 because it'll give me MUCH more pull in 4th and 5th. I can pass on the highway without downshifting.

Steve