That Fabulous 3rd Gear Grind..
 

Hello,
First i'm going to state what i've done to my car hoping it helps with any replies and answers:
Early 12A, Originally built to SCCA GT3 rules which explains it's Large 'Street Port'. Was told 240HP to the flywheel with it's original 51mm Weber and 4 inch short primary collected header.
Same 4in. header but running the stock rear exhaust with RB 'Street Port' muffler.
Wasted Spark.
Heavily Modified 13B Nikki Carb.
Quarter Master V-Drive Twin Disc Clutch, 7.25" Diameter. Has matching Steel Flywheel.
THE TRANS is out of a 87-88 Non-Turbo car, and i have confirmed that's what model transmission it is. Stock shifter for a 85' model, and i'm currently running Royal Purple 75W-90 but i'm switching to Idemitsu Manual Transmission fluid.


Here's my issue: The original trans was a stock 85' model trans, and of course it had the fabulous 3rd gear grind on upshifts when coming up from 2nd when you were driving it hard.(i was told this was normal).. I finally destroyed 3rd gear and put in my current 87-88 NT trans. I love it, and would like to keep it like new as when i installed it. You can tell the syncro's are in good shape.
I haven't had as many grinds into 3rd but when i take it above 6K it's about a 50/50 chance it'll grind. I've even had it grind into 3rd on some downshifts.. Only 2 times so far, and i've had the trans in for a total 3000 miles. I do not know how many were on it before, it was given to me by a friend.(Like i said it shifts greattt though)

My questions:
1. Is it the 3rd gear grind normal when driving hard?
2. Do maybe i suck at shifting?(Shit i've been doing it for 8 years and have had many say i'm good at it) What can i do to help?
3. What have others done to make it easier to shift? Don't tell me it's the oil i'm running.. I've tried everything under the sun.
4. Could maybe the engine be revving so quick that the syncro's can't keep up?
5. Could it be my clutch somehow? It's new, and i know everything's in perfect working order.

My comments:
I know i'm pushing the clutch in all the way when i shift.
If i suck ass at shifting, read the second question in question 2.

I've got to get off here.. So if you have any comments, concerns, questions or answers post them. I think i haven't forgot anything..

Any help is greatly appreciated.
-Crispin

Feel free to treat me like i'm stupid.
Enlighten me. :nod:

BTW, i've also tried slowing down my shifts.

I've driven a few old-school ribcase trannies that had a third-gear grind, but none of the later trannies I've used have had that problem. Second gear, sure. Maybe try some ATF?

ATF definetly helps,
I'm just indecisive because ATF isn't made to handle the loads that gear oil is. If it was just a strict Race Car maybe I'd just use straight ATF, but it's not. It's my Daily Driver and my Autocross Slut. So I need my tranny to last, not just shift good.
I'm thinking the Idemitsu Manual Transmission fluid will help, it's made specifically for MT use.
I've always ran different gear oils and different ATF/Gear oil mixes but never a high dollar MTF like this stuff, hoping it'll help a little.

1. no
2. maybe, you should be able to shift with just your fingertips.
3. is there oil in the shifter box?
4. usually light flywheels make it better.... less mass for the synchro to accelerate
5. yeah if the clutch is hanging up it'll hurt you

in my experience 3rd is the first gear to break if you're racing.

Switching to Redline 75w90 gear oil made all the difference in my TII. It had occasional 3rd gear grind and really bad 2nd gear. After new oil and bushings, it shifted like new up until the day I sold it. I'd recommend doing the diff too while you're at it.

While I personally run an ATF/gear oil mix all the time in my turbo'd and regularly abused daily driver and haven't had a problem (nor do I expect to in the future), if you're concerned you could do a 50-50 mix, drive it around for a while, then drain and replace with your gear oil of choice. The detergents in the ATF will still help clean the tranny out.

Checking the shifter box oil tonight. Otherwise everything else is good. I'm concluding the RP gear oil is worse, because i haven't had grinds on downshifts till i put it in.

This will FIx it!!! Put ATF in her and drive easy for a week. Drain that out, put two thirds Redline MT90 and 1/3 Lucas oil treatment..... problem should be solved...

I also found Poyal Purple to be NOT helpful in an older transmission. Seemed good at first, but (especially under extended use, where things have time to heat-soak) shifting got noisier, harder, and very un-smooth. Went back to castrol with an quarter-shout of Lucas. Much improved.

Interesting observation about RP. I put it in my tranny a few years ago. Fast
forward to today and I've started noticing the 3rd gear sync issue on upshifts as
well. I think I'll change it out again. Not sure what I will use yet.

If I can't fix it, I'll just get another SA tranny and rebuild it completely. I've done
manual tranny rebuilds before and its not that hard or expensive.

I just don't have the time to do my own trans. Otherwise I'd build and modify my own, but, I lack the knowledge and time.
So far one morning of driving with the Idemitsu. It shifts easier, a couple times 3rd was 'rough' but no grinds. I think I've been rushing 3rd on downshifts a bit, but still the Idemitsu has helped so far.. Upshifts were perfect. Especially going into 5th gear.


Also, I most def. think the RP destroys synchro's after a period of time.

I want to add.. The Idemitsu I ordered was the 75W-90 from Mazdatrix.
When I got it the front of the bottle said: 'Idemitsu Full Synthetic Racing Manual Transmission Fluid'
There are NO grades, rates or specs on either side of the bottle anywhere whatsoever. On the back it does say it's specifically formulated for High-RPM syncronized racing transmissions.
So, I'm assuming it is not a GL-4, or MT-1 or anytype of rated fluid for that matter. It's specific to what I'm using it for. Which makes me feel all warm and fuzzy inside.

I still would add a shot of lucas!! That stuff is great!!

I've tried it before in many different scenario's. Just never had good luck and I don't get the fuzzy feeling.

Maybe the RP just wears out after awhile. When I first put it in I really noticed the
difference. That was 10 or 20K ago, so maybe it just needs to be changed.

I've never been over to RotorSports, so maybe I will make a trip there and get
some Idemitsu from Bryan and see how it works.

Let me know of your results as I will advise you of mine.
As for my drive home, everything's flawless except for it has a sort of 'notch' on downshifts into third.
No grinding though.

good stuff to know, doing my auto to stick swap soon. clutch kit and flywheel finally came in :), and I think a fluid change will be in order aswell. think I will mix in 20% atf to the full syn we have at the shop. what is cominly used in the shift box and how much?

I used a mix of silicone grease and 140 weight convential gear oil.

Update on the Idemitsu: only one 'notch' downshifting into third this morning. Otherwise it was flawless, I think it's going to continue to get better.

If it does, it does so FAST; was in my car less than a year, and the Beastie gets driven only a few hundred miles a year nowadays.

I've never had a problem with third gear grinding but was having issues with
2nd. I put 50/50 amsoil 100% synthetic atf/racing gear oil and problem is completely gone after I let the oil warm to temp.

Redline worked for me in all my RX-7s: 1st, 2nd and 3rd gens.

It probably will, mine was the same way. I was disappointed on the first drive, but after a few weeks it got better and better.