rich150001

Hi a friend of mine has a twin turbo 93 rx7. After some hard driving, we came to a stop. Everytime he puts it in second, there is a loud griinding noise. I did a search and it seems people reccomended the redline mt-90 fluid for the tranny. I was also thinking that some gear fluid and lucas additive might help it too.

Has anyone fixed or atleast quieted their second gear grinding problems by simply replacing the fluids?

RX7UP

Sounds like the second gear sincro is bad... How long has he had the car?... Did it make that sound before?

dgeesaman

iTrader: (7)

Yeah, fluid alone can help when the pace of a shift sometimes causes a grind, or there is a little extra resistance in the shifter. But if it grinds consistently then the synchro is bad or something is stuck in there keeping it from doing its job. (As a check, try double clutching on the 1-to-2 shift - if this works, the problem is likely synchro related). Also try changing the pace of the 1-2 shift - slow it down, and ease the shifter into 2nd gear. IME it's normal to get some grinds if you shift excessively fast.

To fix 2nd synchro is all of the labor to rebuild the transmission. So it can't hurt to change the fluid, but it's not a guaranteed magic fix.

While it's drained, it might be worthwhile to drop the bottom gearbox cover, put it in first, and spray that 2nd synchro assy with parts cleaner. Rotate it around and look for damage on the teeth or cracked into pieces. But that's going to be a real mess without a lift, so that you can look way up in there without having the oil draining on your face.

There is a complete 2nd synchro and 1-2 clutch hub assembly that was updated in mid-94 that supposedly makes 2nd a smoother shift. But it will cost a couple hundred bucks, which puts you near the price of a used 94+ JDM tranny. I would keep an eye out for a good low mileage tranny and swap it next time the motor is pulled or a clutch job is done.

Dave

rich150001

Thanks for the info. The car grinds no matter how fast or slow he shifts it in second and it happens EVERYTIME he shifts into second. Right now he is avoiding second gear entirely. What was weird is that after we ran it hard, we came to a stop to check out a huge accident. he then could not put his car in first gear. Eventually he was able to get it in first gear but thats when the grinding first occured in second gear.

dgeesaman

iTrader: (7)

If 1st and 2nd have had some problems, it's probably a bent shift fork. Now that it's bent/misaligned, 1st will overengage and 2nd is underengaged (hence the grinding). 1st and 2nd synchro are probably damaged a little bit, and maybe the gears also.

If you decide to swap the tranny for something else, let me know. I'll make an offer on it as is for a parts tranny.

Dave

rich150001

he is no longer having any first gear issues but i'll let you know if we decide to get a new tranny. I guess we'll try replacing the fluid and see how that works. his car has between 360-380whp I believe if that makes any difference on how it could affect the tranny.

dgeesaman

iTrader: (7)

With higher HP, you're talking greater torque. If the clutch isn't released all the way and/or you miss a shift there is that much more load grinding the gears. It's possible the fork bent the first time so that 1st wouldn't go in right, and then bent it back and the problem is now felt on the 2nd gear side. Or maybe it's something with the clutch hub assembly that has the same symptoms. 380hp is still below the accepted 'limit' for the stock tranny, but when something goes wrong inside the tranny case it will go to pot that much quicker (as we've seen here). But putting in another stock tranny is still probably the best route. Most other options won't drive as smoothly or be as cost effective.

Fluid replacement probably won't help in this case, but it may drain out any chips or broken junk that might be contributing to the problem. Strain out the chips so you can take a good look at them to guess what material they are (and where it could have come from).

Again, if you want to remove the bottom cover plate you can visually inspect the 1-2 shift fork - again you remove the bottom cover of the gearbox - the 1-2 shift fork towards the rear of the car when you look up into the gearbox. If it's bent/cracked or the roll pin is damaged then you know what's up. But there is no guarantee the problem will be visible from there, and it could be messy if you don't have a lift to work from.

Dave

RX7UP

Answer please^

rich150001

I believe only a few months but I will check with him. It did not grind before this night. It just started happening after he ran it hard.

rich150001

Just to let anyone know that is interested. We changed the transmission fluid and his car runs great now.

dgeesaman

iTrader: (7)

That's surprising. What did the old fluid look like? Were there any metal shavings or dirt?

Dave

toddm

what fluid did you put in it?

rich150001

He is on vacation now but I will ask him once he gets back. He is having a new issue though. The LSD left differential bracket is broken. Anyone know where he can buy it used or cheap? I'm thinking a junkyard I guess.

dgeesaman

iTrader: (7)

The for sale forum, for Fritz Flynn.

Dave