Hot Rod Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter #1
hey guys, iv'e got a 68 camaro with a 377 , the 355 rear thats in it now is leaking like crazy. from the pinion seal . i replaced the seal once , and it's still leaking. so as my rear end knowledge is limited to what iv'e seen done on tv, i don't whant to bang the thing any worse than it allready is , i'm ganna get this rebuilt by a pro. if i go from the 355 posi that's there now to a 390 or 410 what kind of rpm increase am i looking at. now at 60 mph i'm about 28 or 2900 . the car is a 4 spd m21. any ideas would be great.
 

·
Drive it Like u Stole it!
Joined
·
163 Posts
for any 1:1 gear ratio, at 73mph you'd be spinning 3550 rpm with a 3.55, 3900rpm with a 3.90, and 4100 rpm with a 4.10, respectively. since you dont have an overdrive, that 3.55 is probably the highest streetable gear ratio you can put in. you can probably put in more gear, but your freeway rpms would be nasty! if you ever drag race the car, you should probably try to match your trap speed closest to the ending gear's top speed. for instance, if you trap 110mph or slightly less, and that's pretty much the top of 3rd gear (6500 rpm) using a 3.55 rear end, that's the gear you should use to more efficiently do a 1/4mi. i guess it would be feasible to maximize out your transmission and go through 4th gear, but that would mean a higher numerical rear gear, and a top speed of 110 mph in 4th!
 
1 - 3 of 3 Posts
Top