I posted this a while back and only got one response. Informative, but I'm hoping there are more people out there that have come across this and know exactly what I'm talking about. Here's the issue:

I have the 3sp automatic (not sure of the real name...TH125?). Anyway, normally it drives fine. Off the line is very responsive and quick. Going up through the gears during acceleration is quick (Hypertech chip). However, after the car warms up, the symptom is this. When I decelerate, and then try to get back on the gas quickly, the trans is reluctant to engage (similar to driving a stick and missing a gear). My RPMs will go up, I back off a bit, then it engages. It's like it's searching for which gear it should be in. It happens more so with the "rolling stops" that I so frequently do. Sometimes under hard and fast deceleration, I come to a complete stop, then I feel a "bump" from behind. I think it's the trans finally deciding to go back into first. I also need to mention that I do have a main seal leak between the trans and engine but I keep fluid in it. So like I asked, is the trans going bad or is that just the way the Fiero runs? If I need a new trans, I don't see the need in paying $500 (local going rate at the shops) to replace the main seal. Also, if I do need to change the trans, which one should I get? I think I've heard of a 4sp trans out there (name?). I may also put in a turbo or go with the much touted and easy to swap Camaro 3.1(4). Thanks in advance.

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BLADE

'86SE
Engine rblt by Jasper (Going V8 in 2004..Hopefully)
Hypertech Chip
Low-temp Fan Switch
Low-temp Thermostat
Grand Am rear brakes
215/45-17 front, 235/45-17 rear Falken Ziex ZE-502

I've been fighting a bad TCC solenoid lately, and when it's only half-failing it sounds ver much like the symptoms you describe. As you slow to a stop, at about 5mph the RPMs jump by 100 or two and you get a surge forward as if you'd been bumped from behind.

When the engine is very hot, you come to a chugging stall at every red light.

For me, the problem is clearly the aforementioned solenoid. I've been told that they're a perennial problem on Fieros. It might be the same for you. There’s a diagnostic procedure published in the shop manual which will help you find out if a bad chip or a bad solenoid.

Since you mention having an aftermarket chip, I’d cast a jaundiced eye toward the center console. Maybe even just reseat it for grins.

The quick-n-dirty way to tell, is to just pull the connector off the transmission. Don't do a lot of highway driving this way, because you'll generate more heat and rev higher when cruising level at 55, but it won't hurt anything in the short run.

If your symptoms vanish, you've identified the problem.

I would check the tranny fluid level first. Make sure the trans is at operating temp, on level ground, engine running and in Park. Also check the color and any unusual odor on the fluid. It should be a transparent red, not dark brownish red.
Check the TV cable adjustment and make sure the TV cable in not kinked and moves freely. Also have someone shift it into all the gears while you watch the shift linkage to make sure the shifter cable moves freely and is hitting the correct detent.
You may want to clean out the trans oil cooler by disconnecting cooler lines (mark them top/bottom for correct reinstallation), spraying some brake clean into one line and using compressed air to blow out fluid, repeat until clear brake clean comes out.
You can replace TH125C (3spd) with the 440T4 or 4T60 made in late 80's and up to mid 90's. I would look for one from a 3.1 engine because it should have proper gearing. Look here http://www.fieroaddiction.com/index2.html for more 4speed auto info............Paul

quote Originally posted by badger: As you slow to a stop, at about 5mph the RPMs jump by 100 or two and you get a surge forward as if you'd been bumped from behind. When the engine is very hot, you come to a chugging stall at every red light. Since you mention having an aftermarket chip, I’d cast a jaundiced eye toward the center console. Maybe even just reseat it for grins. The quick-n-dirty way to tell, is to just pull the connector off the transmission. If your symptoms vanish, you've identified the problem.

The "bump from behind" is exactly what happens.
I don't come to a chugging stall at lights though.
I don't think it's the chip because it was doing it before I installed the chip.
Pull the connector? I'm sure I can find it, but what will that do? Keep the trans engaged?
So you're saying try the pulling of the connector 1st? If it's not that then it's likely to be the TCC?

quote Originally posted by Paul Prince: I would check the tranny fluid level first. Check the TV cable adjustment and make sure the TV cable in not kinked and moves freely. Also have someone shift it into all the gears while you watch the shift linkage to make sure the shifter cable moves freely and is hitting the correct detent. You may want to clean out the trans oil cooler....... You can replace TH125C (3spd) with the 440T4 or 4T60 made in late 80's and up to mid 90's. I would look for one from a 3.1 engine because it should have proper gearing. Look here http://www.fieroaddiction.com/index2.html for more 4speed auto info............Paul

The fluid level is kinda a guesstimate since I have that main seal leak. So there is ALWAYS red fluid leaking :-)
TV cable? Shift into all gears? Sounds like you're referring to a manual. I have an automatic.
Didn't know I have a trans oil cooler. Thought that was an aftermarket item.
I'm going to check, but I think the Camaro engine I referred to earlier is a 3.1. Would that be the trans you are referring to?

If it is the TCC, which would be the best route? Replace the TCC - Replace the trans with the 440T4 or 4T60 - Replace the trans and engine at the same time? Just wondering what would be the most cost effective considering I'm staring at $500 for a main seal repair anyway.

quote Originally posted by Blade_69: The fluid level is kinda a guesstimate since I have that main seal leak. So there is ALWAYS red fluid leaking :-) TV cable? Shift into all gears? Sounds like you're referring to a manual. I have an automatic. Didn't know I have a trans oil cooler. Thought that was an aftermarket item. I'm going to check, but I think the Camaro engine I referred to earlier is a 3.1. Would that be the trans you are referring to? If it is the TCC, which would be the best route? Replace the TCC - Replace the trans with the 440T4 or 4T60 - Replace the trans and engine at the same time? Just wondering what would be the most cost effective considering I'm staring at $500 for a main seal repair anyway.

Normally when the TCC goes, it either won't lock up (excessive rpm on highway) or it stays locked up (engine stalls at stop). TV cable or throttle valve cable runs from throttle body around thermostat housing to top of tranny. It connects to tranny with a 10mm bolt and the connector is black oval shapped. If it is bad it will cause a slipage. Has the throttle body been removed lately? The TV cable should be adjusted whenever it is disconnected from TB.
It could be the TCC, but you described slipping, which it shouldn't do even with a bad TCC. You can shift an automatic, P-R-N-D-L . The reason I mentioned that was on some TH125C trannys there is a bolt connecting the shift cable to the shift lever. Sometimes the bolt can come loose. If someone shifts into all the gears, you can watch the cable and lever to make sure thay are not slipping.
Camaro tranny is a longitudinal tranny, not transverse. You would want a transverse 4T60 from a GM FWD with a 3.1 engine.
All Fiero automatics have an oil cooler. Is your tranny front seal leaking? Low fluid level will cause it to slip. If the front seal is leaking badly, your only choice would be to take the auto out and have it resealed, but an overhaul would prolly be needed........Paul

I have a TH125C in my pontiac 6000. Nearly the exact same tranny as the fiero uses, and I've had very similar symptoms to what you describe. As was mentioned previously, check the fluid level, as that is the most common cause for the delay in "finding the gear". Even if it is full, change the fluid and filter. I had frequent slippage, and that solved it; not expensive either. It cost $60 including labor.

Regarding the feeling of the bump from behind, as far as I can tell, your guess is right. I believe that is when the tranny is hitting first. Mine has done that for over 40k miles and as far as I can tell, it is normal. One thing you might want to look at is your dogbone though. The downshift puts torque on thge mounts, and if the dogbone is shot, you will feel the engine rocking on the mounts which definately would feel like a soft bump from behind.

Hope this helps

quote Originally posted by Blade_69:So you're saying try the pulling of the connector 1st? If it's not that then it's likely to be the TCC?

Pulling the connector will rule out the TCC. When you pull the connector, the Torque Converter Clutch lockup solenoid (TCC) will never engage, and therefore can't get stuck. So if the symptoms vanish, then you know where the problem is. If the symptoms remain, you at least know where the problem isn't.

Once you've ruled that out, only 362 possible problems remain. I also made the foolish mistake of "assuming". The more experienced mechanics here point out that you should start by checking the fluid level, and move on from there.

Good luck!

Thanks everyone. Once I decide on where to start, I'll let you know what happens.

I believe that the earlier reference to "manual" was not talking about a manual transmission but was instead refering to a shop manual that would explain trouble shooting of the problem automatic transmission.

Every automatic transmission comes from the factory with a transmission oil cooler. They are buried inside one of the radiator tanks. The cooler that you refer to as not having is an auxiliary oil cooler.

One thing I was wondering is if you have checked your lower transmission and engine mounts. A loose or bad mount could allow the transmission to move around, possibly changing the positions of the TV cable and shift lever.

I don't think it is the TCC as that has one of two symptoms. Either the engine stalls hard when you stop at a light or the TCC won't engage (which is very subtle). Based on my (quite limited) knowledge of automatic transmissions, I would say that (if low fluid is not a problem) the problem is your TV. The TV cable tells the transmission how hard you are pressing on the pedal. The transmission uses this information to downshift when you stomp on the gas pedal. It also tells the transmission to shift at higher RPMs if you are pushing hard on the gas pedal. One way to check this system is to accelerate at two different rates. First, accelerate slowly. Notice at what speeds and RPMs the transmission shifts at. Next, accelerate quicker (while still being safe). If the transmission shifts at the same speeds and RPMs, then the TV cable is not doing its job. The rest of the system that controls the shifting is internal transmission stuff. That is probably best left to the professionals.

Blade,
I don't think that your engine rear main seal is leaking if the fluid is red that's leaking on the ground. It's probably the trans input shaft seal. Tranny has to come out to replace it/reseal it. One thing you may already be aware of is, if you remove the tranny for whatever, it's always cheaper to put the exact type of tranny back in. You mentioned that you were considering a 440T4 in the place of your 125c. That does need replacvement/modification of the rear trans mount and shift selector mechanism as well as an extra vacuum line piped in etc, etc = higher costs to install.
As for the TCC diagnosing check this other thread https://www.fiero.nl/forum/Forum2/HTML/050541.html#lastpost

ps: sent you three pm's. Did you get any of them?

quote Originally posted by Bazooka: Blade, I don't think that your engine rear main seal is leaking if the fluid is red that's leaking on the ground. It's probably the trans input shaft seal. Tranny has to come out to replace it/reseal it. One thing you may already be aware of is, if you remove the tranny for whatever, it's always cheaper to put the exact type of tranny back in. You mentioned that you were considering a 440T4 in the place of your 125c. That does need replacvement/modification of the rear trans mount and shift selector mechanism as well as an extra vacuum line piped in etc, etc = higher costs to install. As for the TCC diagnosing check this other thread https://www.fiero.nl/forum/Forum2/HTML/050541.html#lastpost ps: sent you three pm's. Did you get any of them?

Thanks Bazooka. At this time, as much as I'd like to, I think I'm going to wait until I do the engine swap and do the trans at the same time. So right now, I just want to fix the leak and drive happily for a while. I did get your pm's but there was nothing there. They only included what I had written to you.