sharkbait20

I have put about 100 miles on the new gears that I had installed (FRPP 3.73A's). They are pretty quiet up until 55-65ish (fastest I've gone with them so far) at which point they start to whine noticeably louder than other speeds. Whats even more odd is that deceleration between those speeds (55ish-65ish) is LOUD (compared to the acceleration in those speeds and especially compared to any speed 0-50).
I'm not sure what specs the installer's used as far as backlash and pinion angle, but I am thinking that one of these specs is not in par with what is recommended thus causing the excessive whine through these speeds; is this wrong?

Because they are still being broken in, I have been unable to really "get on it", but so far I have not been able to notice any difference between my stock 3.31's and these new 3.73's. I am thinking worst case scenario, but in the back of my mind I am worried that I got shamed and purchased a set of 3.55's or 3.331's packaged in a FRPP 3.73 box.... without tearing apart the rear end, is there any way to tell or gain perspective on whats in there?

Thanks,
sharkbait20

gipht1

Even without being able to get on them, you should be able to see the difference in terms of where your RPM's are at at whichever speed! Meaning if your car was normally at 2.5k rpm at 70mph (just for example not accurate) , with the 373s you will be at 2.8-2.9k rpms at the same speed. So you might not be able to feel them yet but your rpms should be higher at any given speed then stock 331s! There is an exel sheet running around the net somewhere that has values at where your rpms will be at at certain speeds!

mwinter501

I wondered the same thing when I went from 3.55s to 4.10s, during break in period that is. I looked at the highway RPMs and saw a difference. Once I was able to punch it, I could feel the difference.

I had 4.10s in a fox body a few years back and the city driving was noticeably difficult, thats what threw me off. But, in the S197s, I hear that the transmission gearing is such that the 4.10s aren't as harsh.

I doubt you got scammed, just wait till you can punch it and I bet you'll feel a difference.

sharkbait20

Yeah I was trying to look for a difference in the RPM range but it had been almost a week since I had driven the car and couldn't remember what speed correlated with what RPM on the old set.
Still waiting to hear some opinions about the backlash specs and such... thanks

stangit9090

I didn't break my gears in whatsoever.

They're as quiet as my factory gears.

SUP3R D4VE

[QUOTE=mwinter501;7002834]I had 4.10s in a fox body a few years back and the city driving was noticeably difficult, thats what threw me off. But, in the S197s, I hear that the transmission gearing is such that the 4.10s aren't as harsh.QUOTE]



If that is true, how much of a difference is there with 4.10s on the s197 and 4.10s on a 99 gt? I have a bud who has a 99 gt with 4.10s and its crazy how fast he has to shift to 5th gear, is there a diffence in tranny gears for the 99 and s197s? Will 4.10s be as bad in my car compared to the 99gt?

Sorry for stealing the thread, just had to ask.

gipht1

THERE IS A CHART out there that shows the numbers. as far as backlash n that stuff goes, Im sure someone will chime in eventually. Maybe at 250miles get on the throttle once and you will feel the difference. The more i drove mines the more I realized how freaking sweet gears are... In fact im planning to put mines on in June/July!

mwinter501

[QUOTE=SUP3R D4VE;7002930]I'm not a guru like others on this forum, so someone please correct me if I'm wrong. I had a fox body mustang ('92 LX 5.0), so I don't know if the transmission was the same on that as a '99 (I would bet on it not being the same). I can only speak from experience on the '92. City driving was much less user friendly: always shifting and starting from 1st gear on a hill was very difficult. This could have been due to the fact that I learned to drive a manual on this car, but it seems like there is a huge difference in drivability between the '92 and the '07.

The obvious tradeoff is that the 4.10's in the fox seemed more aggressive (faster in acceleration) than the '07.

If you have any more questions, feel free to PM me. I don't want to steal the thread any more than I already have.

alkemist

My '06 automatic accelerates pretty damn good with 4.10's.

Did you buy your gear set brand new from a reputable vendor? I was told by my installer once gear whine starts, it's not a guarantee they will go away since you are already wearing them in unless you get a new set. There are cases where you can actually get a defective gear/pinion cut too but that is extremely difficult to tell as explained to me. TBH, I get some minor decel gear whine, which most ppl can't seem to hear.. but if this drives you up the wall, you need to take it back to your installer and have them take a look at it.

mwinter501

I dont mind gear whine as much, I like to imagine I have a blower.