Downshift to 4th

[Eagle7]

I just finished the first weekend on my first transmission rebuild. All seemed good except it was sometimes quite stubborn downshifting into 4th. The prior transmission (not the one rebuilt) also had trouble going both down and up into 4th. I know 4th gear is a little different animal than all the others. Is there something I missed on the rebuild that would cause this? I replaced all the synchros, but not much else.

I'm not rev-matching (yet), and I assume that would probably eliminate the downshift problem, but my question here is about the rebuild issues, not my driving.

Thanks,

[joeracerx95]

I just finished the first weekend on my first transmission rebuild. All seemed good except it was sometimes quite stubborn downshifting into 4th. The prior transmission (not the one rebuilt) also had trouble going both down and up into 4th. I know 4th gear is a little different animal than all the others. Is there something I missed on the rebuild that would cause this? I replaced all the synchros, but not much else.

I'm not rev-matching (yet), and I assume that would probably eliminate the downshift problem, but my question here is about the rebuild issues, not my driving.

Thanks,

If you aren't talking about a 1st gen RX7, ignore my post. You don't mention anywhere what model Mazda you are asking about.

My experience, which has been echoed by some others, is that the 1st gen RX7 transmission is reluctant to cleanly change from 5th to 4th. I have found that if I disengage 5th, let the shifter settle in neutral for a moment with no pressure on it, then gently pull the shifter into 4th, it works. This takes a small modification in my driving by pausing in neutral but since this is a downshift it doesn't cost me any speed on the track.

3rd to 4th has never given me an issue.

YMMV.

[mbuskuhl]

I had a 2nd Gen tranny rebuilt with synchros and it still sucked after the rebuild (regular tranny shop). I had problems changing gears and the tracks I run are mostly 3-4 only, sometimes 5th if a roval course. I was missing shifts, grinding gears, having to force things sometimes, just not any fun.

About 3 race weekends later I let a new shop (race shop) that knows more about these tear it down and rebuild again . It turns out all the shift forks/rod ends were worn out and they had to be changed. They also changed all bearings, synchros, 5/R shift hub, 3/4 hub slider, 1/2 hub slider, all slider springs and 3rd gear. 5th gear was also changed but just because I want the .756 (this is all from the receipt). Since then, I have been happier with my tranny but not paying for two rebuilds, especially the cost of the 2nd one.

Not sure if this helps at all, but as you can see mine needed a bit more than synchros.

[tom_sprecher]

I have found that if I disengage 5th, let the shifter settle in neutral for a moment with no pressure on it, then gently pull the shifter into 4th, it works.

+1

[Eagle7]

Thanks guys. I think you've helped me quite a bit. Much appreciated.