swieduwi

Ok here is the question. I want to replace the rear differential gears on my 2005 Mustang GT with a Automatic Trans
I am looking for better track times but still want to drive to work and not kill my gas milage. I have a SCT Xcal2 Tune
and my trans is tuned to shift harder at wot.

mustangman02232

id say 4.30s but they might kill your milage a little too much, you have to do atleast 3.90s though, and you already have 3.31 gears, 3.55s are a waste as are the 3.27s and lower, because they will make your car slower.

281GT

Your car already has 3:31s'.
3.55 or 3.73 isn't going to make enough of a difference to justify the cost.
2.73's are meant for cars that do not have an over drive and need good highway mileage. All they will do is slow your car down and possibly reduce the mileage. Only GM would be stupid enough to put 2.73 gears benind something with an over drive.
The 4.10 might be a little much for the highway depending on how fast you like to cruise.
I'd say go with the 3.90's This will make a substantial difference in acceleration and won't kill your highway mileage.

drbobvs

I'm getting gears in my auto this thurs. Was going for the 3.55's but the installer said I wouldn't feel much of a difference. He talked me into 3.73s. This will raise my RPM about 250 on the hwy. 1800 at 60 to 2050 and 2100 at 70 to 2360I. I'll post back after the install.

MACHINE

I also went with Motive 3.90's purchased thru BREENSPEED. I also was worried that 3.73's wouldnt be enough, and 4.10's might be a little too much...installing them Friday AM...will let you know how she feels..

757GT

I am going with 3.73s in my auto. I heard that with the 4.10s in the auto '05 it makes second gear almost worthless because the gears are so close together. It would go into 2nd gear at like 5800 RPM so it would have to shift immediately into 3rd. That is just what I heard though. I also have talked to people that dropped 2 tenths of a second in their 1/4 with the 3.73s. I had 3.91s in my '04 GT auto and liked them.

drbobvs

Well, I chickened out today. Did not get the gears installed. I'll think about it for a while. Might want to do other mods such as TB first... 757, 2 10ths in the QTR doesn't seem like much at all for going from 3.31 to 3.73s. If this is all you get I'm glad I held off. Anyway, in about a month or so the car will be off the road for the winter anyway. I guess I'll decide over the winter. Maybe do it in the spring when I fire it back up.





'05 GT premium. auto. IUP. Shaker 500. C&L CAI with XCAL2 by Brenspeed. Sequential Taillights. Chrome exhaust tips my MRT. Midwest Autogear engine cover.

[IMG]local://upfiles/16153/5780E7DC53C147DD96EEFE6B3F3CC053.jpg[/IMG]

The Ghost

I found a complete rear end with factory 3.55 gears on E-bay. I was considering it based on cost for the whole thing vs. a gear change. So...we don't think 3.55 is enough of a difference to notice? If I could get at least .5sec off my 60ft. it might be worth the price to buy it.