Arachnyd

This seems quite odd to me. On the race track, I can get it into 3rd gear once, but every time I down shift into 2nd and then spool it up trying to shift back into 3rd it won't go. sometimes it even "feels like" it engaged, and the shifter is pushed up, but there is no third gear there (still in neutral). Shifting from 4th to 3rd works perfectly every time, and when I'm just driving down the street- even at high RPMs, I can't replicate it, but it happened over, and over, and over again without fail on the track trying to get from 2nd to 3rd.

It also got worse every time. Last time I had the car out there it had a little hang up but went into gear alright, but there was enough of an odd feeling to mentally note it. The first hour or so it did the same thing this week, gradually getting firmer and firmer, finally culminating into me "thinking" it was in gear a few times but it was still in neutral (even with the shifter up).

No gear grinding or anything. I've lost syncros before and I get a good grind. None of that. Shifting back into neutral/2nd and then going back in to third eventually got me back there. May have dropped RPMs slightly during the fiasco.

Finally gave up shifting into 2nd because I couldnt get back into third and had to rely on leaving between 3rd and 4th.
Cooled down, bled the clutch, went back out- same issue from the getgo. but on the street it drives fine.

Any takers? I guess I don't know transmissions all that well, but it doesnt sound like a component of the clutch assembly, a synchro, a gear, maybe the shifter or a shifting component? I thought maybe I bent one of the forks but then I feel like 4th shouldn't engage properly, and it engages perfectly smoothly even when shifting at about 114 mph from 3rd to 4th which is right when the rev limiter hits.

I've searched and found issues regarding 2nd and 4th, but nothing related to 3rd. Does anyone that knows these transmissions better than me want to offer some insight?

OneCylinder

Just a guess and I don't know these transmisions better than you but my guess is a worn 3rd gear sencronizer. Guess #2 is maybe that 1st to 4th lock-out.

Good luck!

Arachnyd

If a Syncro is worn, it wouldn't have trouble engaging, but rather it would not "sync", right? Or in other words, gears would grind, not "feel like they were in gear but not be".

OneCylinder

Like I said it’s all guess-work on my part since I’m not personally experiencing the problem. My knowledge is limited to a Muncie 4 speed and a couple of toploaders that I rebuilt years ago (many years). Each of the individual gear castings consists of the actual gear teeth and the dogs (similar to a spline) on the side of the gear. The input shaft also has dogs with the same diameter and spacing as the dogs on the gear. A collar with the same diameter and spacing but female in configuration is moved by the shifting fork attaching the input shaft dogs with the gear dogs. The synchronizer is usually a brass ring with dogs in the same configuration as the dogs on the gear and fits loosely between the gear dogs and the input shaft dogs. (look up Wikipedia)
The purpose of the synchronizer is to synchronize the rotation of the gear dogs and the input shaft dogs. Since the synchronizers are a softer metal and they absorb the initial thrust the dogs will wear making them less efficient . My guess is that a worn synchronizer may not be an issue at the lower rpms but at higher rpms it’s not performing. Manual transmissions are tough but they do wear and especially under racing conditions and synchronizers and bearings are the primary wear items. I don’t race (wish I could) but sometimes it feels like I’m in reverse and when I let the clutch out there’s nothing there. The good news is that Chevy moved the tranny to the rear for weight distribution; the bad news is that the shifter is six foot long.
Anyway good luck with it, get a professional diagnosis.

Arachnyd

Thanks for your thoughts.

I'm trying to perceive how a synchro could wear so it wouldn't go into gear, yet it wouldn't reproduce grinding.

I'll get professional diagnosis, I just know what they will say "Buy a new transmission". I swear if I don't diagnose it ahead of time every time they just tell me to replace everything haha. Oh well.

I thought maybe someone would say "oh thats a common issue- just adjust the shifterl linkeage" or something.

kenlilley

first of all what year is the car, and what tranny does it have? Can you go into 1st and reverse no problem? It could be a number of things like the shifter box is loose, or you might need to adjust the linkage from the shifter to the transmission.

OneCylinder

Take a look at this link http://en.wikipedia.org/wiki/Manual_transmission it has a good photo of the dog clutch which is the shifting mechanism. The dogs on the gear and the dogs on the synchronizers are arrow shaped pointing towards the output shaft dogs and the dog collar. As a gear is engaged the dog collar engages the synchronizer dogs first. This is a point of wear as with time and heavy use the arrow points wear eventually rounding off becoming less efficient.

Going back to your original post. What else would keep you out of 3rd during high rpm upshifts but not high speed down shifts or low rpm up*****? I don't know.

I don't think you need a new tranny. When I was young we beat up our cars and trucks pretty good and I've seen worn, split and shattered synchronizers. The bearings that support the components also wear and fail. I think that a good shop should give you a decent price if you need a rebuild.

dahogan

'99 FRC, which should be a BW T56 . Maybe I should go ahead and replace the shifter/shifter box because I was thinking abotu doing that, and adjusting the linkage at the same time. That could narrow out those issues.

I've only done a transmission on older cars, but I'll do some searching for adjusting the linkage. That doesn't sound like its probably the issue because it wouldnt be related to speed or RPMs, but it shouldn't be too hard to do all the same. Thanks for your thoughts

Arachnyd

Oops... That was me ^ I was accidently in dahogan's account.

Arachnyd

I've never gone to a shop with a transmission issue and not had the response be "you need a new transmission"... not once. One car , 3000GT VR4 was shredded to pieces a month after I bought it- they couldn't rebuild it. My 2010 Camaro lost its transmission at 1,050 miles new (faulty part eventually recalled)- Couldn't rebuild it, had to put a new one in. Ford transmission was grinding, told it had to be rebuilt. 1980 Camaro Z28, same story different car (grinding in 2nd, needs to be rebuilt).

So if every time I have a transmission issue and take it to a shop it needs a new transmission, I can't help but expect the same here! Hope thats not true. I really don't want to have to spend more than a few thousand bucks on it right now, so hopefully it can at least be rebuilt.

The issue with things like the dog gears or the syncros, is they always create a grinding sound. If its not grinding, then its not engaging at all. What would keep a transmission from engaging? Sounds like what kenlilly alluded to, bot those wouldn't be related to RPMs or speed, which leave me confused... I'm leaning towards a fork/internal engagement mechanism. I think the next step is to find a shop I can trust where I live and see if they can open it up and look inside.

Thanks for helping walk through and research this with me- I appreciate it! I was hoping (like many other issues) to get a response like "oh thats a common issue- its a lockout malfunction XYZ" but we aren't always that lucky!

OneCylinder

Does your vette have the 1st to 4th lock-out?

Arachnyd

I don't think so- Is it possible to have that taken out with a tuner?

I don't recall it EVER happening, so I think the guy before me got rid of it when he had it tuned. I don't get the light come on either, so maybe it either wasn't on the 99s or it was tuned out?

dahogan

...thanks for the up dates.

z06tolbs

Any updates on this? Did OP ever figure out what the issue was?