4T45 transmission

[Redog]

OK I've been reading about it on Alero Upgrades and I found it pretty interesting.

I thought the only FDR ava was the 3.05 in the Alero and the 3.29 in the GAGT, however I was very happy to see that there is also a 3.63 and a 3.91 FDR in some other models.

I did one of those drag racing cals on the net and the "ideal" rear end ratio (since they only deal with RWD cars) happened to be 3.63 :D

I know that I'll need more RPM at highway speeds to keep at 70 MPH (I think it was 2350 vs the 1975 I'm at now at that speed) but will I notice a difference in 1/4 mile times or just the 60 foot?

When I went from 2.73 to 3.42 in the Delta's rear, my 1/4 mile times stayed the same, but with the 3.42's I would spin off the line, even with the 20.50 @ 63 MPH 307 in the car :cry:

Also the little LSD thingy (looks like a box to me) that is on there for the 4t40? Since the 40 and 45 are the "same" will that fit the 45? And where can I get these upgraded clutch packs for the 45?

[kwhauck]

Raybestos makes upgraded clutch pack. The LSD should fit I believe.

Also Ken, I think I heard somewhere that a the gear ratio for FWD vs. RWD are different. For example a 3.94 FDR in a FWD would be equivalent to 4.56 in a RWD. I couldn't find anything when I was quick searching google.

[G.I.Ceo]

You can buy a upgraded LSD from this website. http://www.engineered.net. I know a lot of guys put these in when they rebuilt their trannys on GA's. I would check them out. They are the only place you will find a performance LSD for this tranny.

[mfuller]

You can buy a upgraded LSD from this website. http://www.engineered.net. I know a lot of guys put these in when they rebuilt their trannys on GA's. I would check them out. They are the only place you will find a performance LSD for this tranny.

Yes, but be prepared if it takes 9-12 months to get it.

[Shiwnath]

Is it worth it to upgrade the 4T45? I've read that they dont do well in higher HP applications, but i guess a 4T65 swap would be a big drain on expenses. How many horses are you at Redog?

[G.I.Ceo]

A rebuilt 4t45e will hold 300hp. There's guys running turbo charged and supercharged GA's with these and having no issues. The only time you need to do the swap is if you are pushing around 325hp or more. A rebuilt 4t45 will be enough.