Hi,

I have a mess on my hands dealing with mechanics and need someone to bail me out...

I have had no problems with my transmission shifting up until the first time my mechanic had to remove the transmission to change freeze plugs out on the engine. Then it started having problems shifting from 2nd to 3rd.
Took it back and they did something and it worked okay for a little while then they changed the oil pump out and it wasn't changing correctly in either gear. I could manually change as long as I waited until it got to between 2500 and 3000 RPM.
This same mechanic told me it was going to be $500.00 to rebuild the vacuum body. I didn't believe them.
I took it to another mechanic and he replaced the modulator and it started working fine.
Going down the Interstate the other day it kicked out of 3rd back into 2nd. I stopped at the gas station and found that the transmission fluid was real low. Put some in and it worked fine.
Went to an appointment, started back down the highway and it wouldn't change from 2nd to 3rd. Now I'm back to the original problem.
Noticed that when I crank it up and drive it down the road/Interstate it's fine. If I stop, turn it off and then start back down the road it will not change from 2nd to 3rd.
Then, I stopped, rested for a while, started back up and it changed into all gears the way it did when I first got it.

Any ideas?

Thanks!

 

Put how much in?

Sounds like fluid level to me. Start it in the drive way and let it warm up. Once warm, check the transmission fluid level.

 

and make sure that it's sitting on level ground.

 

Awesome. Thanks for the quick reply.

I checked it and it is close to 3/4 full in relation to the maximum level mark. Would that cause it to not change from 2nd to 3rd?

 

You should actually drive the car and have it shift into every gear, including reverse. Then check the fluid with it in park and idling..

 

check that the kickdown cable is good and adjusted properly,i dropped a trans once when i was young and forgot to disconnect the cable at the carb and i stretched it out and had shifting problems.not saying that is your problem but it only takes a few minutes to do.

 

I took it off at the instructions of the second mechanic and it didn't drop from 3rd to 2nd whilst going down the road which may be just coincidental but it still did not shift up to 3rd correctly.
Thanks!

 

you said that at one time the modulator was replaced and it worked fine so another suggestion would be to check the mod. it might be adjustable,by removing vacuum hose and inside the nipple there is a small screw.i forget which way you turn it but you could check with a trans guy.also check that the hose is on really tight and that there are no cuts or holes in the vacuum hose.hope you figure it out and if you do let me know.

 

My assumption is that the mechanic knows this and has eliminated these items as potential problems. I don't know for sure if either mechanic checked the hoses but I asked them both could it be the problem and they said no.
The first time the problem showed up there was a crack in the hose and they cut it off at the break in the hose and put it back on. I don't know that either one of them have actually replaced the hose from the carb to the trans.

 

everything you said points to the mod.valve,chevys are known for the tee that screws in the manifold behind the carb for loosening up and filling up with gunk.the vac. hose should go from that tee to a steel line that is attached to the bellhousing bolt then down to the mod valve.when they pulled the trans they could have damaged the line anywhere so you will have to check it yourself.also any vacuum leaks and engine timing can affect the shiftng of the trans.especially on a vette, you have all the vac.lines for the headlight and also inside the car under the dash,one time my override hoses fell off and the car ran like crap untill i turned the radio off and heard the hiss in the car.also cutting off a bad piece of hose tells me its a bubba type of mechanic.any good mechanic will replace the hose and check what i explained earlier just to keep the customer happy.

 

Just had the modulator replaced. Is that what you're talking about? I did look at the vacuum hose. I'm not sure what I'm looking at but if you're standing on the left side, looking behind the carb. there was 3 lines going into what looked like a raised area. One, had a short piece of rubber hose and then connected to a metal tube. I pulled this rubber hose off very easily and if that is the vacuum line going to the transmission I can't imagine how it is working. I would assume the connection would have to be very tight since it's vacuum we're talking about.

 

If you follow that steel line, it runs back to the trans dipstick tube and follows it on down. That tube has hoses on each end for the connections- either end can split or fall of and weird things happen. Even the steel line can be crushed and pinched off.

 

It sounds like the hose that was slit, cut off and reattached was probably dry rotted. If so, it lost it's elasticity and needs to be replaced or it will continue to split and leak.

 

Could very well be. I will replace it. Something odd, but I drove it the other day for about 60+ miles and didn't have any problems at all. Someone suggested that it may be heat related.