1. Home
  2. Chevrolet Trucks
  3. Transmission shifts REALLY hard in '99 Tahoe

Transmission shifts REALLY hard in '99 Tahoe

Hello all!

I have a '99 Tahoe and the transmission shifts really hard from 1st to 2nd and get's a little smoother from 2nd to 3rd and so on. This happens when the transmission is hot only. When the transmission is cool it changes as smooth as can be. I bought the vehicle used and the previous owner said it had always done that. Supposedly, it was checked out and told "that's just the way they shift". Bull crap!! If that were the case it would do it all the time. Anyway.... I've heard of a lot of problems with the tranny from '97-'99. Maybe GM will make it good if it is a known problem. ??

Has anyone else experienced this? Any ideas??

Thanks, dphillip

Reply to
Dawn Phillips
Loading thread data ...

scan it for codes

odds are it has a P-1870 stored

two choices: new valve body, or find a transmission shop that will ream and sleeve the offending valve bore

Reply to
Gary Glaenzer

Thanks so much Gary. You are right. It is the P1870 code. I think it is "transmission component slipping". The valve body is what I've been told is the culprit. What about the rest of the components? Reckon how long they will last. The deal is... I bought this off of a Ford lot and got the warranty for a Ford dealership only. I'm trying to get the problem diagnosed before I take it in. I'm sure they will want to patch it instead of replacing the t'mission. You know how warranties can be.

How much should replacing the valve body cost?

Thanks, Dawn

Reply to
D Phillips

the P-1870 is a pretty generic code......as you say, 'transmission component slipping'

but 9 times out of 10, it is due to wear in the bore containing the Torque Converter Clutch regulator valve, which sends oil to the 'apply' side of the TCC disc, and the rest of the unit is OK

take it to a transmission shop that does a lot of GM trucks, and ask for the 'Sonnax' valve

they'll know what you mean

G

Reply to
Gary Glaenzer

Just thought I'd throw this in.. I had a load in my truck the other day (and today) and I thought I'd give the tow/haul mode a try. upon pressing the button the light came on the dash.. I took off driving.. And not really paying attention to the tach or speed.. I felt it shift really hard from 1st to 2nd. and I mean hard.. I slowed down and let it shift back into first.. then slowly accelerted and it shifted alot smoother.. It appears to only shift hard on high at high RPM's, is this normal? It acts like it just slams into 2nd. Driving with Tow/Haul off everything shifts smooth at any RPM range.

Just curious..

Adair

Reply to
Adair Winter

Thanks again, Gary.

This "Sonnax" valve is the valve body, right?

Just checking. I'm taking it to the Ford dealership for the repair and I want to know if they are dicking me around.

Thanks, Dawn

Reply to
MD Phillips

I have a '99 Tahoe. Is the tow/haul mode standard on these?

Thanks, Dawn

Reply to
MD Phillips

no, the 'Sonnax valve' is an aftermarket repair to the valve body

and a Ford dealership will either not know what it is, or refuse to do it

Reply to
Gary Glaenzer

Reply to
kdm

Reply to
Dale C.

next time (there WILL be a 'next time', trust me), get a print-out of the actual codes retrieved

I'd bet there's a P-1870 in there somewhere

Reply to
Gary Glaenzer

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.