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OD and tc lockup seem to be intermittently disappearing on my 95 park avenue ultra. I have 149xxx on the clock, on what I assume to be the original transmission so I realize it's a possibility it needs a rebuild, but the symptoms don't really seem mechanical to me.

All shifts and smooth as butter and there is no slipping in any gears, even WOT shifts are smooth and pleasant. Most of the time, OD and tc lockup come in just fine, but sometimes they won't. I made a 230 mile trip on Thursday through the mountains, most of the time not even down shifting to 3rd given the torque of the supercharger but plenty of shifts throughout the trip, and no problems at all with getting into OD. I then made a 60 mile trip the next day and everything was fine until I went to pass a slow moving vehicle in a short time, having to use WOT and down shift to 2nd. After this, the transmission did not shift back into 4th, only 3rd. It remained this way for the remaining 25 or so miles, with no apparent attempts to shift to 4th. The car sat for 5 hours and I drove it on the return trip (60 miles) without any passing and OD was present and working just fine the whole trip back. Today I made the 230 mile trip again but prior to it, was doing some in town driving and had to use near WOT for a short time to avoid being hit (probably not relevant, just the only variable I can see so far). The car sat for about 20 minutes prior to leaving for the 230 trip. OD worked just fine for the first 60 miles, then suddenly, while in cruise control at 59mph, the car down shifted to 3rd and would not shift back to 4th for the next 50 or so miles when I pulled over for a quick nap. The car was off for 12 minutes and when I started up again, the remaining 120 miles was completely normal, which perfectly functioning overdrive. It probably shifted between 3rd and 4th/TC 20 times during this drive due to speed changes without a hiccup.

When 4th is gone, the only weird thing that happens is the RPMs when (only when) coasting. Here's a video. I only touched the throttle before 4 seconds in and at 21-34 seconds.

Click here for the video

Any ideas? It doesn't seem to be heat related and doesn't seem to act like a mechanical problem to me, so I'm unsure.

What is the condition of the fluid and how long ago since the filter was changed?

I dropped the pan and replaced the filter less than 5k miles ago. Fluid was old but not too terrible. The pan was pretty clean other than a small piece of what appeared to be a nylon washer, but I'm not sure where it went.

I would suspect the TCC Apply valve: http://www.sonnax.com/system/tech/84754-16K-TECH.pdf

If you can get a scanner on your car, you may notice a P0740 (TCC Circuit Malfunction) code that will NOT throw the SES light when you lose overdrive. When you restart the car and everything is normal, the code will disappear.

Would the code show up in the history, or do I need to catch it when it's acting up? Would that cause loss of 4th gear entirely or just lockup in 4th? I counted 2 shifts from a stop to 60mph and was running at around 2800 rpm IIRC, which would be 3rd gear. I would assume the TTC apply valve only applies TCC lockup? Or am I wrong to assume this? Also, would that part be replaceable with just the pan dropped or would it require a tear down?

You'll lose 4th gear completely, and from my experience, the code will show ONLY when it is acting up. When it was happening to me (1995 SSEi), I was able to clear the code while driving and immediately the car went into 4th and lockup without issues until the code tripped again - be it 5 minutes or an hour later. Alternatively, I was able to stop, shut off the car and immediately restart it, and regain 4th gear for a little while until it happened again. 60mph at ~2800rpm sounds like you're missing 4th entirely. The problem seemed to occur most when hot, or after driving aggressively.

For replacement, the side pan needs to be removed. This involves dropping one leg of the subframe. It's fairly labour intensive... I had mine taken care of under warranty as part of recently done trans work.

Had a very similar problem on my 94 SE, before and after a rebuilt trans. (Finally exploded the coffee can on the original trans!) I did not specify the Sonnax upgrade, just a rebuild with shift kit and adjustable modulator.

Long story short, this happened 30k or so after the rebuild (and after the required-for-the-warranty 10k pan drop/fluid change) , I dropped the pan, replaced the filter, installed a good oversized viscosity-controlled stacked-plate tranny cooler, and added GM Automatic Transmission Seal Conditioner, along with Lube-Gard and new Dexron 3 fluid to bring fluid "just above" the full line on the dipstick. No more OD dropout or 4th gear loss so far, after almost 3,000 miles. Granted, not a long-term test, but the tranny seems much happier! Firmer shifts, and just a little better MPG.

This "fix" has been related to me as a "short-term" fix for a dying tranny, but I will swear by my results. Even if it's short-term deal, it gets me by for now. Better than another $2,000.00 tranny!

God luck, and let us know your results.

From what I understand, the N/A cars didn't have a tranny cooler from the factory and the S/C cars did, is that correct? So what you're suggesting is (based on the fact that I just replaced the fluid and filter and already have a tranny cooler) I should add seal conditioner and Lube-Gard?

I'll talk to my transmission mechanic friend that helped me change the fluid and filter and use his lift and see what I'll be in if I decide to change that TCC apply valve. Depending how much I'll be in, maybe I'll just see if I can't find a lower mileage 4T60E to swap in instead.

Schlotzky wrote:The pan was pretty clean other than a small piece of what appeared to be a nylon washer, but I'm not sure where it went.

Thats a thrust washer and is pretty important. I think a rebuild is in your near future?

Schlotzky wrote:From what I understand, the N/A cars didn't have a tranny cooler from the factory and the S/C cars did, is that correct? So what you're suggesting is (based on the fact that I just replaced the fluid and filter and already have a tranny cooler) I should add seal conditioner and Lube-Gard?

I'll talk to my transmission mechanic friend that helped me change the fluid and filter and use his lift and see what I'll be in if I decide to change that TCC apply valve. Depending how much I'll be in, maybe I'll just see if I can't find a lower mileage 4T60E to swap in instead.

Correct, NA cars had no external trans cooler. Unless maybe it was optional, HD use, trailer package, etc.

My transmission guy loves Lube-Gard, and uses it with all his rebuilds. I used the GM Trans Seal Conditioner against his advice. And it seems to have helped. For now.

If you decide to replace the TCC apply valve, I would suggest the Sonnax upgrade. If I had known about it at the time, I would have had my trans guy install it with the rebuild.

I have been friends with several trans shops and trans mechanics for many years, and they all recommended the Lube-Gard additive. That's why I use it with every trans service on ALL my cars. (170k plus on my 1999 Crown Victoria, still works fine, and fluid is nice and RED!)

Keep us updated, please.

1fatcat wrote:

Schlotzky wrote:The pan was pretty clean other than a small piece of what appeared to be a nylon washer, but I'm not sure where it went.

Thats a thrust washer and is pretty important. I think a rebuild is in your near future?

Guess so. Got in the car today to pick up a lighter for fireworks and guess what? No first gear! Whoopie!

I took it to a tranny guy and he said it would be stupid to tear it down with 150k on it to fix a sticky valve--just drive it til it dies...little did I know that'd be a week later.

What are my options here? The thing has 150k on it and I was thinking of selling it to buy a truck. With a blown tranny it's obviously worth almost nothing, and I do still love it and was unsure of the idea of selling it. I have a mechanic who will do a full overhaul for 1500, or I could see if I could find a used one and have him swap it in for maybe 3-400 bucks plus cost of transmission. I then did a bit of research and found that there are up to 12 different versions of the 4t60E which cuts the chances of finding the right one down quite a bit.

I'm not opposed to keeping the car for quite a while longer, but what kind of life can I expect out of the engine and such? I also feel that selling the car as is would likely cut more than 1500 off the value so maybe I should rebuild it and then decide whether to sell or keep it?

Did the supercharged cars come with a different version of the 4T60-E? Like an HD version or something? Or was that just 97+?

I found two transmissions under 50K miles for 500 bucks from N/A cars, one with 2.84 ratio and one with 3.06. Stock I understand was 2.97 and 3.06 was tow package?

All Supercharged cars got the -HD differential for their respective transmission, however, the internals of the trans are identical to the non-HD trans, the only difference is the chain, differential, housing and axle.

3.06 wasn't a tow package, it was the "sportier" ratio.

My buddy reminded me changing gear ratios is going to screw with the computer systems so I better stick to stock. My RPO sticker is completely faded, is there a way I can confirm my gear ratio using the VIN? I found a tranny from a supercharged car for 600 with 50k miles, I think I'll go that route if I can.

Punch your vin in on www.compnine.com using their VIN de-coder.

FWIW, you need to find a trans from a 94-95 car, IIRC. The newer ones won't work, neither will the older ones. Any 95 supercharged trans will have the same ratio as your car.

Thanks for the help! I picked up a 78k mile tranny from a 95 s/c park ave for $500 + $75 core and spent $122.73 on axle and TC seals, filter and fluid, then did the swap myself. Returned the core for a total cost of $622.73 and about 16 hours of my time. I was lucky enough to find a guy that let me use his lift for a case of beer, a mowed lawn and a little help on another car. I also tracked down the vacuum leak that was throwing code, so now everything is ship shape. It's nice to have my car back.

Thanks again!

Glad to hear you go it going... always feels good to have your car back... Especially one you like

whered you find the tranny? i cant find any around my area lol

Schlotzky wrote:Thanks for the help! I picked up a 78k mile tranny from a 95 s/c park ave for $500 + $75 core and spent $122.73 on axle and TC seals, filter and fluid, then did the swap myself. Returned the core for a total cost of $622.73 and about 16 hours of my time. I was lucky enough to find a guy that let me use his lift for a case of beer, a mowed lawn and a little help on another car. I also tracked down the vacuum leak that was throwing code, so now everything is ship shape. It's nice to have my car back.

Thanks again!

WOW!! You did great!! Nice job!!!!!!! - BC