GM syncromesh tranny oil change done and now bad noise - help!

[NSX604]

I've been searching the threads over and over and came to the conclusion to go ahead with the GM syncromesh 2 to 1 formula change. Did it due to 3rd gear syncro light grind. After the change, went around the block and everything was fine. Grinding gone. Parked for a few hours then BOOM... A real bad grinding noise. I went through the gears, and its not the gears. I can roll forward and backward only going straight because as soon as I turn the wheel past 10 degrees, there is this bad grinding noise. From theory, it sounds like when the differential is not even something is grinding.

To give a better description, I can go straight - forward/reverse and through all my gears without any problems. Gears are fine and 3rd gear syncro does not act up anymore. It is only when I am turning while going forward or backwards that this awful cabin shaking grinding noise occurs. Wife confirmed noise from back of car. More grinding feel in cabin rather than loud noise.

Any suggestions or help or previous experience would be much appreciated. ...or if I missed a previous thread, please guide me.

Thanks in advance.

 

[garthed]

Sorry to here about your problem. I just did the tranny fluid last weekend. I had no problems. Sorry I'm not more help

 

[Zennsx]

I've had my 2-1 mixture of synchromesh in my car for 4000 miles .My transmission operates flawlessly. Do you think it could be a coincidence?

 

[EIFFEL]

try go back to Honda MTF, I had the tried Redline tranny fluid and experience the same noise, Honda MTF took care of it for me.

 

[NSX604]

try go back to Honda MTF, I had the tried Redline tranny fluid and experience the same noise, Honda MTF took care of it for me.

I will try this first. Hopefully it is just the GM fluids that don't agree with my tranny and rear diff. Keep my fingers crossed. I will keep posted.

Thanks for all your feedback. Please post more if anything to suggest.

 

[smhrednsx91]

I used GM and it works great. I do not understand how changing the oil can affect steering. Did you leave a tool in the car which wedged in your suspension or drive train or mess up your steering somehow??

 

[NSX604]

I used GM and it works great. I do not understand how changing the oil can affect steering. Did you leave a tool in the car which wedged in your suspension or drive train or mess up your steering somehow??

It has nothing to do with steering rack or what you describe. It is the diff that is acting up due to the oil being too thick. When you drive your car forward/reverse, and turn the wheel past 5 degress, your inner and outer wheel spin at different rates. Therefore your diff is now off center and the inner cog and outer cog will spin at different rates. For some reason the GM syncromesh did not agree w/ my diff and made a grinding noise. ( ...and I'm praying that this is the case)

UPDATE: I spoke to a Acura tech today when I was buying Honda MTF. This is a very common problem that they have a lot of NSX's in general coming in after different grades of tranny fluid are used. Apparently the worst being Redline synthetic (maybe just a certain grade, did not confirm). GM syncromesh seems to work great in some and not in others. No way of telling until its done. In my case it worked for my syncro feel as my gear box feels awesome. Unfortunately my diff didn't like it. ...my 2 cents for those reading this. I will update again as I am about the jack my car, crawl under, and pull the plug. Back to Honda MTF. For those of you reading this now, keep your fingers crossed for me. I hope theres no permanent damage. I never made it past 1st gear and over 2000rpm as I just left the house when I heard the noise and back I went. ...to be continued

UPDATE: FIXED!!!! Went back to Honda MTF. At first it was still there but faint. Then I jacked all 4's and spun the rears, and let it sit for a few hours - for the Honda MTF to saturate all gears. Just took her out for a slow test run around the block and noise all gone. Now going for a shakedown rip. Will update.

UPDATE: Shakedown went great. Tranny never felt so smooth. My 2 cents... try HONDA MTF first prior to anything else. Honda designed it that way for a reason. I don't think GM had X'ers in mind when developing syncromesh.

 

[4AU4LIFE]

UPDATE: Shakedown went great. Tranny never felt so smooth. My 2 cents... try HONDA MTF first prior to anything else. Honda designed it that way for a reason. I don't think GM had X'ers in mind when developing syncromesh.

Glad everything worked out for you. This is going to be a dumb question but doesn't Acura put the Honda MTF in it from the factory??

 

[NSX604]

Glad everything worked out for you. This is going to be a dumb question but doesn't Acura put the Honda MTF in it from the factory??

You are 100% correct. Let me clear up what I did (wrong). Honda does put their own MTF from factory. Honda only suggests their MTF in their tranny's. I went against this by reading about 50 threads saying GM syncromesh (2 to 1 formula) will get rid of notchy 3rd gear grinding. Keep in mind there are about 50 threads on this topic that talk about GM's syncromesh but probably thousands of people just doing normal Honda MTF and not really creating threads about it b/c it's just a normal tranny oil change.

Long story short, it worked great for the gears. Notchiness went away. ...but then my differential hated it b/c it was too thick and locked up. Changed back to Honda MTF and everything is fine. My notchiness is gone too. I think it was just time for a tranny oil change. I Should've just gone w/ Honda MTF to begin whith. I was talking to the Honda tech for a while to get some info when I went in to get the MTF and he stated this is a common mistake and they get a lot of NSX's towed in. Most of the time it's a synthetic that causes this same problem.

CAVEAT: Don't try and reinvent the wheel - go with what Honda designed for our cars. (...my 2 cents from my more than 2 cents worth of mistake)

 

[4AU4LIFE]

That is very good info. I kinda feel like I should change mine back to the Honda stuff now. I didn't have any problems before I went to the GM stuff and haven't had any problems now but don't want to create any if I don't have to. Honda techs put it in there for a reason and I'm certainly not going to second guess why they did. Although it seems like I already did by changing brands. :frown: