83 caprice , transmission not engaging drive gears

[cas4all]

Hey , my transmission had no slipping was running fine . Oil level was ok , recently added 1/2 quart , cause it has some small leaks .
I go to drive away other day and none of the drive gears or reverse would engage .
Mechanic thinks transmission locked up . Kind of hard to condemn my old baby considering it was running fine .

Would the TCC solenoid do this or the ECU ?
i recently reinstalled the bar going to starter that was disconnected for 5+ years because i was having slow crank issues .
This transmission problem occurred 2 days later

I am thinking it might have made the ECU unit go bad , since the starter had not a good ground for so long ?

[Blue Bowtie]

I doubt that the starter mounting or grounding had anything to do with the transmission problem. The '83 used either a TH200-4R or a TH700-R4 depending upon the engine installed. If your trans has a square pan it is a 700-R4 (first year for that trans in a Caprice), and an elongated/tapered pan would be a 200-4R.

Neither of these use the ECM to shift the transmission, but only to control the converter lockup, and some of those early ones still used a vacuum switch to lockup the converter instead. In either case, it isn't the ECM. It would be good to verify the oil level (ruinning.hot) and possibly connect a test pressure gauge to read line pressure in various ranges.

[cas4all]

i will also ad that since i owned the car i could always remove the key from the tumbler while it was IN gear .

[Blue Bowtie]

Can the vehicle be moved a foot or two when in neutral?

Know what transmission is installed will make a difference for the diagnosis.

[silicon212]

In '83 you should look in the trunk, there should be a 'Service parts identification' decal. Look for an M code. MD8 will be a TH700R4, MW9 would be a TH2004R.

If you have no drive in any range, double check the fluid level.

[cas4all]

i am not finding that decal . it has a SQUARE tranny pan it shifts into neutral and moves when in neutral , reverse or any other drive gear
i believe the decal fell off a few years ago , if it was the one on the hood of trunk

[Blue Bowtie]

If the pan is square it's a TH700-R4. Just to be certain the TV spool and sleeve are not stuck, with the engine off manually open the throttle fully while observing the TV cable attachment. Once you see how it moves, operate that cable 15-20 times to be sure the valve is free. If you do this simply by moving the throttle the engine will likely be flooded from the accelerator pump action, so move the TV cable only.

It is also possible that the transmission filter is either fully clogged or has fallen out of its retainer/seal. If the filter has clogged the pump will be starved and cannot develop pressure. If the filter has fallen out the pump will only draw air and not develop oil pressure. In order to check this the transmission pan needs to be removed, and all the trans oil capture when doing so.

This is a good excuse to change the trans oil and filter anyway. Expect to use about 7 quarts to refill it once the filter is replaced.

If you find foreign material in large amounts in the pan, take a photo and post it for analysis.

[cas4all]

First , thank you for the replies , hopefully i will drop the pan this week . that detent cable seems to be operating fine and doesn't appear to be broken I was also trying to locate the Transmission Vacuum Modulator to see if trans oil is coming up into the engine . i read in a manual that it could also cause no shifting problem .

[Stealthee]

A faulty vacuum modulator would most definitely cause a shifting issue, but it wouldn't affect the vehicles ability to move.

[silicon212]

The TH700R4 transmission does not use a vacuum modulator, the cable that connects to the throttle controls those functions. It's not a detent cable, it's a throttle valve cable and it is imperative to have it installed and properly adjusted, or the transmission will fail.

[j cAT]

I have a 1984 700R4 4speed auto in camaro. what happened to me was I lost all upshifting. 50K miles on it. it was a broken plastic impeller part. tranny had low pressure.

one of GM's worst trannys. when I had it repaired the shop knew what it was before they opened it . they had so many back in the day.

[cas4all]

why then does the autoparts store have both a modulator and detent cable that says it fits a 83 caprice classic ?

[Stealthee]

Because as Bowtie said, there are two different transmissions that came in the year.

[j cAT]

Originally Posted by cas4all

why then does the autoparts store have both a modulator and detent cable that says it fits a 83 caprice classic ?

so do you have a 4 speed ? if so then a 700R4. detent cable is on drive side of carb. check that it is not stuck pull on the end of the s/steel cable tit.

[silicon212]

in 1983, the 3.8 liter V6 (229cid, based on the 305) was the base engine for the car, and this was only available with a TH350 transmission. This is why those parts are available for that year. The TH350 does have a vacuum modulator. The TH200C, 2004R and 700R4 use a throttle cable instead.

I have a rant about auto part stores though. Their databases often have incorrect information. An example is in the 90s, I had a 1975 Pontiac Grand Am. This had the Poncho 400ci engine with a TH400 transmission. According to Autozone's computer system, this car was never available with a TH400 transmission. In reality, the car was ONLY available with a TH400. Take with a grain of salt what they tell you, and do your own research.

Jcat - the cable on a 700R4 is not simply a detent cable.