I am running a 4.10 in my 92. I absolutley love it, great acceleration even though I top end early. My question is this, I drive it on the interstate once in a while but the car is smooth as silk until I hit 70 mph. From that point I get a very fine viberation through the drive line that gets worse as speed increases. I was wondering if in fact I am over spinning the driveshaft with such a tall gear.

 

Probably. Is it a steel, or aluminum driveshaft? They say all driveshafts will shake at certain speeds, even when properly balanced, due to harmonics and such. A steel driveshaft is gonna shake a lot more because it has significant more mass. I run 3.73's, and get a vibration at about 70-75mph, that gets worse through about 80mph, and then goes away if you go faster yet. 90mph+ is smooth as glass, but not very practical for my commute. I try to cruise at speeds just over the worst of the vibration - but I will upgrade to an aluminum shaft some day.

BTW, can you even hook the 4.10's on street tires with the 700R4's low first gear? My lowely little 305 can barely stick the tires with 3.73's and a mild converter when launched easy, and with too much pedal too soon will smoke them right up. What kind of rpm are you turning at 70mph on the highway? Converter? Lockup?

Just curious - I love my 3.73's and 4.10's sound like a lot of fun as well.

 

You cant get to happy with first gear or yes it will burn the tires off. From a roll you can stand on it and let it kick down into first and eat as long as the tires are hot...lol. I also think part of it is I am not getting all my HP to the wheels I am seriously due for a new tranny. I was wondering if an alum. driveshaft would be better. But it is a major change from the stock 2.73's. I am running non lock up and turning 3000 @ 70.

 

Generally when drive shaft speed increased the diameter also needs to increase. The drive shaft will distort when it reaches a certain speed, which causes a vibration. Most stock drive shafts are made for much lower RPMs that what you are turning with the 4.10 gears and overdrive. The overdrive transmission allows for lower engine RPMs, but the drive shaft RPMs increase when you change the rear end gears the way you did.