So I've had my '91 z28 for many years now, and while I did have the original engine (a 305) replaced (with a 350- this may have something to do with the problem since its the 305 trans), I have never had so much as a hiccup occur with the transmission. It never dawned on me that coupling that trans/engine might not be a perfect combination- in fact I figured the 305 and 350 trans were the same thing. I only realized otherwise when I went to replace the starter which plugs into the transmission. The 350 starter won't fit into the 305 trans. Anyway, I'm getting away from my topic here:

So yesterday, I drove into the office, about a 5 mile drive, everything was fine, spent a few hours there, and drove to the store afterwards- maybe 6-7 miles. During that trip I noticed that the car wouldn't shift to overdrive- at about 85mph, I was near redline. On the way home from the store (about 5 miles) it seemed to have lost the 2nd gear, so I drove home at around 40 mph (again, near redline).

Today, I have to read up and try to figure out what's going on. So far the info (easy fixes) that I've found on the forum include a 'sticking governor', and low transmission fluid. Here's hoping for an easy fix!

Also- this may have something to do with the cold. It's like -10 degrees here in illinois right now. That is also the factor that is severely demotivating me to go freeze while trying to repair this.

Any help much appreciated!
thanks!
-Kevin

 

Difference? What is this difference you speak of, there is no difference. The flexplate may have been different but the transmission is the same. Adjust the T.V cable and check the trans fluid. Sounds like your T.V cable is out of whack or broken.

 

They gave you the wrong starter. A 305 trans IS a 350 trans. There is no difference.

What SSC said. Check your fluid and TV first. Then post what you found.

-Tom

 

I'd heard that the transmission was the same in either, but I can assure you that the starter IS in fact different and I'm guessing now (as I was then) that its only the flexplate. If you buy a starter from autozone (or wherever) for one, it won't fit the other even though they are similar. The 305 has a smaller opening that it fits into.

Anyway, all of that is besides the point. I'm here at the shop now, and I've checked the linkage (inside the air cleaner, right?) and the trans fluid which was a bit low. I added some fluid and on the way over here it did manage to shift from 1-2 once for a few seconds before I had to slow down. Now we're back to only being a one-gear car. So I guess the fact that it is still able to get into higher gear on rare occasion indicates that there isn't a broken linkage or something, right?

The guy at autozone seemed to have a lot of faith in the idea that it was a dirty trans filter which has not been changed while I've had the car (just turned 160k). But I know that is a big and dirty job to change, I'm not really equipped to do it, so I will probably have to take it in. I was really hoping it was something easy though. Am I throwing my money away there or does that sound like a reasonable guess at the problem? Seems to me that a dirty filter would cause intermittent shifting problems with increasing frequency, not all-at-once symptoms like I'm having now.

Anyone?

Thanks!
-Kevin

 

I wouldent take advice from someone that works at Ozone or any other parts store. If they knew so much about cars they wouldent be working for minimum wage.

If you know what the TV cable is check it to see if its broken, This link is in the tech articals, even though this is a 6 there all similiar and adjust the same. https://www.thirdgen.org/newdesign/tech/detent.shtml

A plugged filter will act the same in all gears not just one, although its a good idea to cahnge you fluid reguardless since you dont know when it was last changed.

 

After I put a 350 where my 305 used to be with a freshly rebuilt tranny... the tranny gave up about two months later. If you haven't had your tranny rebuilt, it would be a good idea to do so now.

 

Okay,
So I still haven't found/fixed the problem, but thought i'd update you guys on the symptoms.

I've figured out how to coax it into 2nd with SOME reliability. If you get going, then redline it in first, let the tach drop down- repeat a few times, it eventually hooks up and you're in second (until the next stoplighrt). I haven't been on a fast enough road to see if this works for 3rd. Anyway, I know not to take autozone employees too seriously, but I have to admit that the transmission filter theory IS looking more plausible since I can get it back in gear on occasion. It's still odd to me that it would enter this condition so suddently. From what i can tell (in what i described above) it is (suddenly) lacking necessary pressure to make the gear switch. The extra RPM's allow it to complete the operation successfully. The trans dipstick does show that it has the proper amount of fluid, so is there a pump that goes bad somewhere? (again, the filter would effect this) I really don't know very much about how transmissions work.
In the research I've done here, it sounds like the governor may be to blame as well (would these symptoms suggest that?). I've tried to find it on the transmission, but have so far been unsuccessful. Any tips on finding/servicing the governor on a '91 Z28?

Believe it or not this is my WINTER car we're talking about. I might just have to take my corvette out of storage early if this keeps up. I'd planned to trade the z28 for a jeep, but its too late now! Anyone want to buy a camaro? ... cheap!?

Thanks for any help!
-Kevin

 

My tranny sometimes does that when its real cold. But it shifts fine when the fluid warms up. By any chance do you have an external tranny cooler, that might be the problem. it super cools the fluid making it sluggish and in combination with an aging tranny and a possible dirty filter might just cause that.

 

Hi again!
Well, I must say that I'm surprised that nobody here has offered a defined opinion of this problem since all other posts I've made to this forum have produced specific, dead-on results from some of the experienced members here. I don't mean that as a criticisim in any way- just that it confirms that this problem is more mysterious than anything I have had before. Also, thank you to those who have already replied- I appreciate the help!

I've generated my own theories as explained in previous posts. Because it IS able to sometimes engage 2nd gear I'm thinking it can't be the governor. Because it needs to get some high RPM's to achieve a successful gear shift, I was thinking it was a problem with the pressure of the hydraulic system that would be effected by the filter/fluid. This still leaves the question of why the shifting problem would occur so suddenly seemingly without provokation. In any case, I took it to the shop today and after a pretty messy struggle, managed to replace the trans filter- possibly for the first time ever, clean out the pan/magnet, and replace the trans fluid. Basically, I wasn't too surprised to see that the problem still existed, however, it seemed to be flowing better and able to shift at lower RPM's now. So at least that was contributing to the problem. I took it onto the highway today and tried to get it into 3rd, but no luck- I redlined in 2nd at 90mph, but still it refused to shift to third.

Are there any other tests/theories that you guys can suggest?
Thanks!
-Kevin

 

Did you ever check the TV cable adjustment?

 

I have to agree with Morley. The symptoms you're describing are what a TH350 does when the vacuum line falls off the modulator, which controls the shift points. The TV cable does this job on the 700r4, so that would be my first suspect if I were you. If everything does check out okay with the cable, then maybe check into the governor. I'm not even sure if the 700r4 has an accumulator spring, but these can cause erratic shifts too when they're broken.

 

Dont know how many time I have to repost in this thread but gee at least tell us you checked it.

All shift kits in some form will shim the accumulator spring to casue firmer shifts, a broken spring will do the opposite and cause super soft shifts, my 1/2 spring was broken and I dident even know it until I put a S/K in.

What you describe Kevin is exactly how a mis adjusted or broken T.V cable will cause a transmission to act. If you continue to drive it like this is IT WILL BLOW UP! CHECK THE DAMN CABLE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Ok, ok!

From my second msg:
"and I've checked the linkage "

Yes, I did check the TV cable based on the advice received here. I guess I should have said 'tv cable' rather than 'linkage'. Maybe I didn't check it out thouroughly enough--? I will focus on doing a second, more thourough check today.

Re: the governor: If the governor was to blame, it seems like the teeth would be missing or the gear cracked internally and this wouldn't allow the trans to shift successfully even at high rpm's? Depending on how dirty and cold I want to get today, maybe Ill check that out too.

Thanks guys!
-kevin

PS: To 84Z28- I don't have an external trans cooler, and the problem is the same from when I first start it (0 degrees) to near overheating (due to overrevving)

 

The teeth break on the governer and it is common easy to check as well. Just pry the round cover near the back of the case (drivers side) off and take a look. The governer slides right out.

 

Recheck the position of the TV cable. If it is broken it will have moved again. Try the setting procedure and once it is set, actuate the throttle linkage by hand (many times) and watch the cable, if it moves from the position it got "set" to then it is broken internally.

 

I checked the TV cable again, and again I can't find any problem with it. However, I will say that the tech article didn't help much, I can't really see from the pics just what is being described. In any case, the cable itself doesn't shift its adjustment, it bottoms out at WOT (and you can't pull any more when its' in this position). Nothing is loose or broken in that assembly. I did put a shim after the cable stop to make it pull a bit earlier to see if that changes anything (the shim takes up a about 1/4" of cable). It does shift differently now, but not correctly.

I stopped in at a mechanic at lunch today who seemd to think it was an internal belt or clutch pack. Another mechanic I spoke with on the phone seems to think it may have to do with the vacuum modulator or a vacuum leak. Is this transmission equipped with such a thing?

I'll post tomorrow with the latest result, but I still welcome any more ideas.

Thanks!
-kevin

PS. one thing I did notice when checking the TV cable is that there are no clicks present (as described in the tech article) when it is moved through its range. Another site that describes the adjustment procedure makes it sound a lot more exacting:
http://www.tciauto.com/instructions/...ble_adjust.htm