Ok, here we go again... As some of you may recall, last week, I changed my tranny oil with Redline 75W90 hoping to fix my grindy 3rd gear shifting. It's been a week now and my tranny did not improve a bit. BTW, it only grinds when I am up/down shifting at high RPM... like above 4K. I can manage to shift without grinding by depressing the clutch longer till it gets in. I sometimes get grind on reverse as well. But I think its only happening when it is still cold.

I searched the forum and read somewhere that it might be my clutch wearing out. So for you experts out there, is it my clutch or my synchro? How can you tell, which one is failing ? I hope its my clutch coz its cheaper to buy a new clutch than rebuild a tranny.

 

It sounds like your syncro, I have the 5th gear syncro problem. Basically, you have a "layshaft" in your trans that turns by itself when you are in neutral and with the clutch in. When you wait a little bit to put it in your 3rd gear (in your case) you're giving the layshaft time to spin down, and lock with the rear end of the drivetrain. I have to go pretty slow with my 5th gear. and just let it fall in.

If you don't get what I'm saying, do some research on google.com on how transmissions work.

Hope this helps.

 

Are your hydraulics good? Did you bleed the clutch? How are the shifter bushings?

I still think that you should give the MT-90 a chance. Its cheaper than rebuilding/replacing the transmission.

 

75-90 is diff oil.... should have used MT90 or MTL. the 75-90 might be a bit too thin for the tranny. moving up to MT90 would help more.

 

Isn't the MT-90 and 75W90 the same except that the MT-90 is straight 90 weight?

 

If you think its the clutch, try bleeding the fluid. its easy to do it with a one way valve (one man brake bleeder) or use the bottle method.

 

Bleeding clutch may raise where it grabs, therefore disengages clutch further from plate/flywheel

 

ok, i'll bleed the clutch tomorrow and if that doesn't help. i'll change my oil to MT-90 if I can find one.

 

i bled my clutch today and nothing has changed. i'll try the Royal Purple since I can't find an MT-90 around here.

 

I think its your syncro... My second gear sucks.... you can't speed shift into it at high rpms, you have to wait a second and slide it in. And downshifting... well all i can say is double clutch.

 

Ok dude, don't waste any more money on fluids. Your syncro is bad, that is it. I wish someone here could have told him if it was the clutch or hydraulics, it would grind in every gear before he bled the damn thing. The 3rd gear grind is the most common and replacing just the bearings and synchros will run you under $500 if you R&R the tranny yourself.

 

I agree with Piranha, it's syncros. As stated, if you wait for trans to slow down(push clutch in and wait) no grinding, it's syncros. Same as downshifting. If you have grinding at a higher rpm, and you don't at lower, and shifting in the same manner....Syncros.The higher the rpm at shift, the harder it is for the synchronizer to bring the mainshaft speed down to match the speed of the cluster gear.
Double clutching will extend the life if syncros are gone.

 

hmmmm.... it sounds like I either need a rebuild or a new tranny

 

yep, i cant quickshift to 2nd at high rpms either and i spoke to the guy that does all the work on my car and he said the sycros are worn out

 

ok, so how much should I expect for a tranny rebuild? how 'bout if I buy a used tranny, how much do you think would I pay for a tranny swap?

 

Used trannys around here are $400-500. Of course wear condition is unknown.
Maybe trade the whole car for a TII.

 

Are you kidding me I've had this car for 3 yrs and no matter what happens I'll keep this NA. I've got a few list of cars beat by it on the road.

 

Get it rebuilt. Then you know what you have. If you can pull it yourself, probably @ $400 labor + parts. Syncros arn't expensive ($70), but while they are in there have them check bearings closely.

 

Ok, I decided... I found a used tranny for $90 with 80K and will have it swapped by a shop for $200 and that includes installing of a new clutch if I decided to get one. What do you think? Is that a good deal?

 

If you go through the trouble with pulling the trans, then you should do everything:

clutch (good time for upgrade)
pressure plate
release/throwout bearing
pilot bearing and seal
front/rear trans seals and front cover if worn
trans mounts should be inspected and replaced if broken
flywheel--resurface or replace(inspect for cracks)
slave/master cylinder and clutch line
adjust pedal height and freeplay
MT-90 to preserve life of the new tranny

 

Well, the problem is, I don't have tools to do the tranny and clutch. I intended to do it myself but the money that I will spend for the tools and my time will cost more than the shop who'll do the work for me. I don't worry about this shop because they've done a lot of RX-7's already.

 

mine started grinding or has a gear noise but in only in 1,2,3 and 5th gear and not in 4th what can that be

 

but it still sifts ok

 

4TH is direct or 1 to 1 your noise is most likely a bearing between the input shaft and the main shaft , in 4 th gear they are turning the same speed thus no noise. 1st 2nd 3rd are underdrive ,4th is 1 to 1 , 5th is overdrive

 

i just put new bearings in 3-4 weeks ago but only 4 of them and new clutch and fluid