1983 Buick Electra Park Ave. Has problem, need help. Long history, but interesting problem

I have a 1983 Buick Electra Park Ave., 8 cyl, automatic with overdrive. I towed a 4000lb camping trailer last year about 120 miles. At the end of the trip the car had a hard time climbing a small hill with my foot all the way to the floor in lowgear. The car seemed to be stuck in a high gear or had no power. At the camp

site the car was over heated.

I had the catalytic converter, muffler and exhaust replaced thinking that the exhaust was plugged. The car had about 100,000 miles on it. I drove it during the week with no problems, but it overheated within 25 miles of home on the return trip towing the camper.

I had my mechanic check the engine and the only thing they found was that the distributor somehow shifted to the wrong side of optimum, I don’t remember the

actual reading, and the car ran fine afterwards with no overheating.

No more towing has been done.

This winter the transmission developed problems, slipping and not shifting correctly. So before having the transmission rebuilt, I had the engine checked again to make sure that the engine was OK, and the engine was fine according

to the mechanic.

I got the car back with the rebuilt transmission towards the end of winter. It shifted rough, and would not shift into overdrive unless I lifted my foot off of the gas pedal as the car approached 60mph. The car had a chatter during shifting through the gears, which was getting worse with use. We also heard a clang coming from the transmission, just prior to coming to a complete stop at a stop light.

I returned it to my mechanic and he returned it to the transmission shop. I believe they replaced the torque converter and sensor.

The car now runs fine around our small town in the cool weather, although it still shifts rough.

When I took the car on 250 mi. long trip. I found that on the highway in overdrive, everything was fine, and the car gave a smooth ride with no problems.

However, when driving in New York stop and go traffic, for over an hour in the warm weather, the transmission started shifting erotically and seemed to be stuck in a high gear. Once the car got up to speed it only displayed lack of power, and once back on the highway, the car performed fairly well with noticeable loss of power.

This is very similar to the problem encountered on the initial towing trip above,

when I had my foot all the way to the floor climbing that hill, the car seemed to be in a high gear even with the lever was in the low gear position.

I returned the car to my mechanic with my complaints, and the car was returned to the transmission shop. I gave them summary of the problems occurred in writing, and told them that the real problem will not show up until you drive it in stop and go traffic for over one hour in weather hotter than 70?.

While in New York I took three one hour trips in the stop and go traffic, two in the warm weather and one in the cool weather. The problem almost did not occur driving in the cool weather. It was noticeable, but diminished. The problem returned with the two trips in the warm weather.

The transmission shop said that they could not find anything wrong. I did not think that they would be able to duplicate the New York stop and Go traffic

around our small towns. They said the rough shifting was fine and necessary to prevent it from burning up. I think they did something with the linkage or cable, I don?t remember.

I talked to my regular mechanic after the transmission shop returned the car. I told him that there was definitely something wrong, and the problem would

probably will not show up until the car is driven in the hot summer weather.

The transmission shop did say that the carburetor needed to be rebuilt, so I had it rebuilt, hoping that would solve the problem. It did not.

My mechanic told me to take it home and bring it back when the problem occurs so he could check it out.

In June, I returned the car to him after driving it in 95? temperature. I only had to drive it about 5 miles before the problems started showing up, and when I stopped for about 10 mins, the car got worse, it would just barely move with my foot all the way to the floor. By the time the mechanic came over to drive it, the car had cooled somewhat and he was able to get it moving, but agreed that there was something wrong.

That was history, now my question.

What possible could be causing this problem.

It is definitely a heating problem, but the car shows no signs of overheating.

Is it possible that I have a head gasket problem that occurs only when the engine gets hotter than normal. Could it be so minor that I can?t find any evidence of water disappearing from my overflow container.

Or is it possible that there is a vacuum leak that only occurs at a certain temperature.

How can I find out?

Also does anyone have any other suggestions.

Thank You, Ray

I would check the transmission fluid cooling system to see if that is flowing like it should be.

I would have the mechanic measure the fuel pump pressure and volume flow. You might replace both the fuel pump and filter and any rubber hoses in the tank line. You might also check the tank for rust that could be clogging the tank sock.

An engine problem can be reflected into the transmission as it uses sensors reading parameters of the engine. If the transmission thinks the engine is producing more power than it actually is it will shift hard, late, and lock out overdrive.

Hope I have helped

Researcher, good idea to check the fuel delivery. Would an '83 transmission be doing any thinking? I thought the controls were strictly hydraulic and mechanical, no sensors.
O.P., I hope you were not towing in OD!

The OP didn’t specify the transmission so I am assuming it is TH400 or an 700R4. Both of these transmissions probably use a vacuum modulator to control line pressure and shift points. Both would also have a mechanical governor. Some of these transmissions also had a TV cable and a electrical driven kick down circuit. One way to consider these interface units is to look on them as the sensors for a hydraulic analog computer. The computer is rudimentary which is why the digital TCM’s do so much better.

Thank you all for your replies. Transmission colling was checked and is fine. car has a transmission cooler installed. I will mention the fuel pump to my mechanic and see what he says. Don’t know which transmission the car has, but will check and reply. Hopefully the transmission shop knows about vacuum modulators and kick down circuits, will check with them to see if they agree. Thank you all again.

The thing about rebuilt transmissions is that there are a number of ways to rebuild them but really only one correct way.
Some rebuilds (term used loosely) are nothing more than throwing new clutches and seals into a tired old transmission. A proper rebuild is going to get new bushings, bearings, updates, etc. along with the previously mentioned items.

Whenever a transmission is rebuilt the torque converter should always be replaced IMHO. Reusing the converter is like building a new engine and reusing a worn out oil pump.

The chatter noise is a bit iffy as that could be caused by too much advance in the ignition timing (if it’s engine related) or possibly by someone not tightening the torque converter bolts properly. Loose TC bolts can rattle and at some point could cause a loud clank when they finally come completely loose.

You can perform a stall test and determine if the trans rebuild was a bit shaky.
Set the park brake and hold the foot brake. Shift into LOW, rev the engine quickly and it should stall out about 1900 or so RPM. Allow the engine to idle a few minutes and repeat this in SECOND gear. Allow to idle and repeat this in DRIVE. Do NOT do this in OVERDRIVE.

The engine should stall out at about the same RPM in all gears; if it revs to 2500 RPM or whatever then you have a transmission problem and it’s back to see if they’re going to stand behind it.
Hope some of that helps.