More transmission trouble... please help!

Hi everyone

I came here asking for help around 4 months ago.
My '99 Tahoe was slipping gears pretty badly, so some suggested I try braking a bit while accelerating to see if the problem was the TC, but it wasn't.

I live in Spain, Europe. I went to the Chevy Service and they said they couldn't repair my transmission and that a new one was 12000€, around 14000$.
As that is probably more than this car is currently worth, I looked around for a place that was used to rebuilding transmissions, and eventually found one that was currently servicing a few Hummers and lots of BMW/Audi/Mercedes and looked pretty well.

They offered a complete rebuild for 3300€ (a bit over 4000$). I accepted it and they did it in less than two weeks.
However, when I went to pick it up and started driving it I immediately noticed something was wrong! The transmission switched gears much faster than before, but every now and again the engine would drop from whatever rpm it was at to 500 (idle). In less than one second the engine would resume the normal speed it had, and all of this without changing the position of my foot on the gas.
It's pretty psycho. It's exactly as if I would let go of the gas to then resume the previous position a second later.

I thought something else was wrong, so I drove around for over an hour and the problem kept reproducing itself.
I returned to the transmission shop the next day and told them it clearly didn't work and they had to fix it.

Well, the car stayed there for over a month, in which they concluded they didn't know what it was but thought it was an electronic problem, which of course the transmission's warranty doesn't cover.

I took the car to my Chevy dealer and he checked the error codes. He got a P1810, but as we didn't know if that was from before the rebuild he deleted the code and told me to drive around to see if I got another code.

I took the car again last week and after checking the codes we got the same code: P1810.

I've looked for some info about it and it turns out it's the automatic transmission fluid pressure manual valve position.

¿Can anyone help me?



SYT

Usually caused by a bad trans pressure control solenoid which GM had trouble with in those years. The pan must come down. It is possible they did something when repairing the unit, loose connector, improper reinstallation and such. See this linkhttp://service.gm.com/gmspo/mode6/pdf/1999/99t53T_CK_aT.pdf

Just a thought, since they had the transmission out and the code has several references to gear ranges being wrong. You might look at the range switch (on the driver side of the trans., has 2 electrical connectors). Usually these connectors break if you try to remove them, but you can remove the whole assembly without unplugging it. This makes reinstalling on the new trans. harder due to the wires, also that switch is adjustable, maybe they didn't get it adjusted properly. Especially since you stated it was like that as soon as you got the truck back. Just a question, do the gear indicators (the "P-R-N-D-2-1" lights) correctly light up as you move the shifter down one step at a time? Basically here is what is going on as the code reads. The computer and the transmission do not agree on the gear the transmission is in. The transmission goes by what position you have the shifter on the column in to select the gear. The computer is told what gear the transmission is in by the range switch on the side of the transmission. If the range switch is out of adjustment, the computer could be told the transmission is in a different gear. Hope this makes sense. Hope this helps.

Good suggestion, klinn.

Just a thought, since they had the transmission out and the code has several references to gear ranges being wrong. You might look at the range switch (on the driver side of the trans., has 2 electrical connectors). Usually these connectors break if you try to remove them, but you can remove the whole assembly without unplugging it. This makes reinstalling on the new trans. harder due to the wires, also that switch is adjustable, maybe they didn't get it adjusted properly. Especially since you stated it was like that as soon as you got the truck back. Just a question, do the gear indicators (the "P-R-N-D-2-1" lights) correctly light up as you move the shifter down one step at a time? Basically here is what is going on as the code reads. The computer and the transmission do not agree on the gear the transmission is in. The transmission goes by what position you have the shifter on the column in to select the gear. The computer is told what gear the transmission is in by the range switch on the side of the transmission. If the range switch is out of adjustment, the computer could be told the transmission is in a different gear. Hope this makes sense. Hope this helps.

OK, I understand what you're saying, I'll go down to the garage to check the gear indicators light up properly, but as for the range switch... I suppose you mean I have to look under the steering wheel for it, but what exactly am I looking for? I'll take a couple pics when I'm down there and post them to see if you can point out what it is ;)

Sorry for the poor mechanical knowledge, I'm usually a do-it-yourself kind of guy; but when it comes to fixing cars I'm a total rookie :dunno:

no, the range switch is on the driver side of the transmission and has 2 electrical connectors to it. Its about 9 inches long and 4-5 inches high. To adjust, loosen the two bolts and then it tilts forward and backward. Usually the two bolts are 13mm, but since it has been removed, they may have been changed. Keep in mind this is a thought, there may actually be an internal problem like maxwedge suggested.

no, the range switch is on the driver side of the transmission and has 2 electrical connectors to it. Its about 9 inches long and 4-5 inches high. To adjust, loosen the two bolts and then it tilts forward and backward. Usually the two bolts are 13mm, but since it has been removed, they may have been changed. Keep in mind this is a thought, there may actually be an internal problem like maxwedge suggested.
so that's not something I could just crawl under the car and look at, right?

Is there any way I can look at this myself without having to take it to the shop?

I know it can be something else, but I'm hoping it is as I'm assuming it'd be an easier fix, right?

yes, the range switch is physically mounted on the side of the transmission, you can crawl under the vehicle and see the switch, it has 2 connectors connected to it. All connections, adjustments, and inspections can be made from under the vehicle and without disassembling the transmission.

yes, the range switch is physically mounted on the side of the transmission, you can crawl under the vehicle and see the switch, it has 2 connectors connected to it. All connections, adjustments, and inspections can be made from under the vehicle and without disassembling the transmission.


Perfect, I'll try to get under the car today and check it out. I'll post what I see.

Thanks a lot guys!