93 RX7 5 speed fluid question/problem

[unnerv]

I have 93 RX7 with a MT. When the Tranny is cold it shifts into all gears, although on GL5 75w90. Before that I has using Neo 70-90HD and had the same problem. When I had bought the car it supposedly had Redline MT90 in it. It is hard to remember since that was 2 years ago, but the problem seem to happen less, but still present.

Do you guys think it might be thinning out as it warms up? Or maybe the synthetics are just too slippery for the sycros? I am debating whether trying dino juice in the right weight or the new amsoil 75w110. What do you guys think?

 

[sky jumper]

oh man the 3rd gen 7 is a sweet ride. I had one for a brief moment...
http://img242.imageshack.us/img242/7479/93rx7before1lh0.jpg
http://img73.imageshack.us/img73/8572/93rx7after1ln8.jpg
http://img177.imageshack.us/img177/2655/93rx7after2gu8.jpg

sorry I can't help with the gearbox oil.

 

[ConfederateTyrant]

If you decide to use Amsoil don't use the 75w-110, too thick and GL-5 does not appear to be all that great, performance-wise, in manual transmissions (that was gathered from what all I have read on here). I would suggest the Amsoil MTG, it is a GL-4 75w-90, and GL-4 seems to be more ideal.

 

[unDummy]

Bleed the clutch, replace the shifter bushings, and use a quality GL4 gear oil like Redline MT90 or Amsoil MTG. Test the master and slave for the clutch. I'd bet that the problem is with the shifter bushings or hydraulics. No gear oil will fix that!

Since its a turbo, I'd consider running a GL5 like Redline 75w90NS or Motul Gear-300.

Depending on the mileage and maintenance history, it might be time for a rebuild. Sorry, but transmissions do wear out.

I wouldn't consider other diff-gear oils, especially the 110 or 140 wt ones. If you want thicker RoyalPurple Maxgear is one of the thicker dual rated GL4/GL5 gear oils. I also don't see any gear oil fixing a mechanical problem.

Another option is trucking gear oil. Mobil sells a Delvac-50 full synthetic GL4 gear oil, or look for any Mack TO-A Plus SAE50 gear oil! These tend to be thick 90wts at a safe GL4 additive level. SAE-50 straight gear oils, in warmer climates, are excellent. I was hoping to keep this secret to myself for a couple more years. Its a great option for Nissans, Toyotas, Mazdas.......

 

[unnerv]

skyjumper, sorry for your loss. Hopefully everyone was okay.

unDummy, The clutch has been bled, master and slave replaced, braided line installed between them in the last 2K miles. I replaced the shifter and shifter bushing at about the same time. I have even swapped in a spare tranny (although one is 115K and the other 120K. the 115K one is in now.) The clutch and flywheel have about 15K on according to the previous owners record.

Since it only happens when everything is warmed up, esp on hot days I though maybe the fliud might be thinning out too much. I have also noticed that when I down shift without double clutching I can hear the gears spinning up to speed sometimes like the sycros are not getting enough grab. Maybe the synth stuff is just too slippery for my old syncros (this happens with both trannies) or maybe the syncros in both cars are shot...but since I can't seem to hit any gear from a dead stop when I have the problem I was hoping it was the fluid. If I can get the car to roll just a hair it will slip in. During the last cold spell where temps were < 50 all day I didn't seem to have any problems at all. If it is not fluid related I guess it could be the TO bearing or pilot bearing going, but I am pretty sure those were replaced when the clutch was done last.

 

[m2200b]

Won't solve the mechanical or possible fluid issue but I've read its easier to line up the syncros when its moving so
your last shift coming to stop should be to the gear you want to start in.

 

[TedT]

I my experience with other vehicles, this problem can be caused by the clutch disk net sliding freely on the input shaft. This can cause the disk to drag on the fly wheel. When I worked on Porsches the solution was to lap the input shaft with valve grinding compound using the disk. On some Porsches the finish on the spline was too rough. After lapping the splines are carefully cleaned and lubed with a very light coating of a thick high presure grease. If your disk is dragging and the splines look smooth, you might try just cleaning and lubing the splines. I have an 84 BMW motor cycle that does this too, only what hot and it also responds to the grease treatment. Just remember to go light on the grease. Ted

 

[unnerv]

TedT, I'll take a look at that next time I pull the sucker open. Thanks for all your input guys. It is sounding more like it is not a fluid problem from reading here. Not looking forward to pulling it apart again. Oh well.

 

[gtx510]

oh boy, FD3S, great car, PITA to work on.

It uses a pull-style clutch (like a Porsche?) so you have to seperate the clutch/flywheel to pull the tranny. (pull the driveshaft before you remove the powerplant frame)
The input shaft is pretty smooth and most shops grease them, but they may not take the time to clean the old grease and crud off. Throwout and pilot bearings usually come with a clutch kit.

FD's get hot. I'd try some thicker gear oil and see if that works for you. Amsoil 110? 50:50 mix of Redline 75W90NS (or MT90) and 75W140NS? Maybe a dino GL-4 + Auto-RX cleansing?
Remove the underbody panel by the tranny?

What brand clutch? Does the pedal engage where you want it to? Have you tried playing with the pushrod adjustment underneath the dash?

And did you make sure that the thin washer springs for the shifter bushings where there?

 

[unnerv]

The clutch was put in before I bought the car, but it supposedly is a centerforce dual friction. The pedal engages correctly. I had my mechanic adjust it when I had the master and slave cyl replaced.

As for the thin washer springs, I did not see one in the old shifter bushing. I replaced the shifter with a B&M and had a new bushing for the ball at the bottom. Was there supposed to be a spring inside that bushing? All the other bushings should be okay since it was a new shifter. I think I will try the thicker gear oil 1st since that is the cheapest most accessable solution. The tranny is rated for a gl4 or 5 so maybe the Amsoil 110 might work. I'll swing by the dealer and see what he thinks.

Thanks for all the replies. If I ever do get this solved, I'll make sure to post back and let you know what works/doesn't.