TT Supra gearbox problems

[MAZMAN]

Hi,
i seem to have a problem with my supra's gearbox.
Ill try to explane.
Say i am racing some1,i put it in first gear,dump it and take off...everything fine so far.
Rev it to 7000rpm and go to change into second gear,Now this is where the problem starts.
Sometimes it takes me a couple of tries to get it into second gear(it feels like not wanting to go into 2nd gear gate),feels like im not engaging into the gear itself.After a couple of goes(by this time ive slowed down a fair bit)it will click into 2nd gear.
Now this also happends with 4th gear,exactly the same way,but no other gear.
I was told it could be the actuall shifter linkage,and was thinking of getting the B&M short shifter to try and see if it is that.
Ive drained the old oil(very dirty)and toped up(ATF DII type) and still same problem.
Is there any1 in here that has this gearbox and possibly knows what goes wrong with them?
Or what could cause a problem like this?.
i havent had time to inspect anything so any idea's are welcome.

The car is a 93 model tt supra,totaly standard,with the 6 speed gearbox.

Thanks for any info.

[TRD-KINGSWOOD]

Sounds like syncro's are worn!! second gear is always the first syncro to fail. I guess they slam second!!!

1st go: Put in a additive. Small bottle of stuff.

2nd: Put in a bit heavier grade oil (lightweight gearbox oil).

If that fixes it. It may well be syncros.

[Shifty]

Before you even do that:

Step #1: Check there's fluid in the clutch
Step #2: Bleed the clutch fully (I'm talking a full bottle of fluid, if not more).

[GSRman]

try this... whent he car is warm (i mean fully up to temp) put the car in 1st, on a flat surface, with the hand brake off, but the car stationary, with the clutch still fully depressed rev the engine quite hard (into the area where the gear shifting prob seems to happen) if the car moves forward, the issue might be the clutch itself..

[MAZMAN]

Thanks for the reply,
first of all,just so you'se know,
the gearbox doesnt crunch gears or anything when all this happens,and thats why i dont think its the synchros.
No noises or anything of that nature at all that would lead me to anything.
I had gearboxes before where if synchros worn,it will crunch when shifting quickly.

The oil that was in it was auto oil,and also on the box itself says to use auto oil..so i did.
Wouldnt the gear oil make it even worst,due to thickness?
Maybe i will try some additive,but it might not be a good idea and ive got no specs as to what oil should go in it.

The clutch reservoir is full of fluid.

And also note that,at anything under the ~7000rpm this problem doesnt exist.

example,
if i race the car and keep the revs low,say around 5,500-6000rpm the problem wont happen,it only happens when i really wanna give it all its got(full potential).

I will probably make some time on the weekend and see if i can adjust the clutch rod and bleed the clucht as well(maybe the rod needs to be extended!).

anyway,keep them answers coming.
thanks a lot guys.

[hcca]

It may well just be your synchros at high rpm.. don't know about Supra boxes (yet!) but I know in the Sigma, shifting at 5500rpm is impossible because of the synchros - no grinding of gears, it's just like hitting a wall and dropping the revs is the only way to get it in.

[Bishop]

My thoughts exactly it sounds like the input shaft is spinning to quick for the synchro and sliding hub to engage. Rz maybe able to help you out he also has a 93 TT supra 6 speed.

[7HEAVN]

were having the same prob at the creek when I spoke to you ?

[Shifty]

To clarify - just because the clutch cylinder is full of fluid doesn't mean it doesn't need to be bled. Every little bit helps.

[MAZMAN]

7HEAVN,
yes,its the same problem i had at the creek,but still had no time to look at it,and its giving me the shits when i race some1 and it happens.

GSRman,
i will try that and see what happens
Thanks.

Shifty,
I know bleeding helps,thats why i said ill bleed the system on the weekend.
Indeed,every little bit helps,and i need all the help i can get.
Cause if its the box,ill be out of money:(

if its the synchros,do you'se think double clutching will help?I havent tried this yet.

[TRD-KINGSWOOD]

Slightly heavier weight gearbox oil slows down the syncros, making it easier to get gears.

[MAZMAN]

ok,
then,does any1 know the specs of what type of oil should be used in this gearbox?

I might try half/half,and see what happens

[Nick]

Don't know if it's the same for the Getrag but for the R154 if this sort of thing starts to happen alot of the yanks put Relline MT90 or MTL in, they say it fixes alot of this.