Shifting issue 98 tahoe 4x4

Brian H · Aug 28, 2011

It just started acting weird...........seems like it has 1st drive and over drive....It doesnt shift until i let off the the gas over 20+mph or a steady gas pedal at around 25+mph. When it shifts it seems like it goes right to drive. No slipping at all just seems like its missing second and the fluid is clean and smells fine. Is it a shift solonoid?

jeffs_62 · Aug 28, 2011

Change the fuel filter.

jeffs_62 · Aug 29, 2011

I guess that may only apply if it's like my Suburban. had a similar issue and was informed that the shifting was based on fuel pressure. $15.00 and ten minutes later, viola, all better. Drives better than it did when I bought it.

crash2 · Aug 29, 2011

jeffs_62 said:
I guess that may only apply if it's like my Suburban. had a similar issue and was informed that the shifting was based on fuel pressure. $15.00 and ten minutes later, viola, all better. Drives better than it did when I bought it.

What year sub?

crash2 · Aug 29, 2011

Brian H said:
It just started acting weird...........seems like it has 1st drive and over drive....It doesnt shift until i let off the the gas over 20+mph or a steady gas pedal at around 25+mph. When it shifts it seems like it goes right to drive. No slipping at all just seems like its missing second and the fluid is clean and smells fine. Is it a shift solonoid?

Sounds like a valve body issue...

Brian H · Aug 29, 2011

New fuel pump and filter. Replaced it when i replaced the engine. It was doing it just before i replaced the engine. Time for a new tranny then crash????? Or could it be a solonoid?

crash2 · Aug 29, 2011

Brian H said:
New fuel pump and filter. Replaced it when i replaced the engine. It was doing it just before i replaced the engine. Time for a new tranny then crash????? Or could it be a solonoid?

Usually its the 1/2 shift valve. There are valves behind the soloniods that stick.

JesterFab · Aug 29, 2011

crash said:
Usually its the 1/2 shift valve. There are valves behind the soloniods that stick.

Crash...
My aunts 1999 yukon lost reverse and overdrive, would this also just be a shift valve?

dirtygoat · Aug 30, 2011

They have a speed sensor that goes out... Also, there's a brake neutral switch that can cause shifting problems...

Does it throw any codes???

crash2 · Aug 30, 2011

dirtygoat said:
They have a speed sensor that goes out... Also, there's a brake neutral switch that can cause shifting problems...

Does it throw any codes???

If that was the case the speedo would not work :awesomework:

crash2 · Aug 30, 2011

s1036's said:
Crash...
My aunts 1999 yukon lost reverse and overdrive, would this also just be a shift valve?

No--thats going to be a tear down and inspect--thats something down deep internal.

Brian H · Aug 30, 2011

dirtygoat said:
They have a speed sensor that goes out... Also, there's a brake neutral switch that can cause shifting problems...

Does it throw any codes???

No codes ... wish there was. I want to figure it out before i go and replace it like i did the engine for something stupid like a fuel pump.:haha:

zukkev · Aug 30, 2011

Brian H said:
No codes ... wish there was. I want to figure it out before i go and replace it like i did the engine for something stupid like a fuel pump.:haha:

Thought you changed the engine due to a burnt valve & the fact it had high miles????

rod:

Brian H · Aug 30, 2011

zukkev said:
Thought you changed the engine due to a burnt valve & the fact it had high miles???? rod:

Because of the fuel pump not feeding the #4 cylinder.

skinny_pedal · Aug 30, 2011

Brian H said:
Because of the fuel pump not feeding the #4 cylinder.

How does a fuel pump not feed one cylinder?

Brian H · Aug 30, 2011

skinny_pedal said:
How does a fuel pump not feed one cylinder?

Just enough fuel to get to the closer cylinders i guess....the number 4 cylinder injector is at the end of the injector cluster . I was told it wasnt getting enough fuel pressure to pop the injector. Replaced the engine and it acted the same...replaced the fuel pump and it ran great.

crash2 · Aug 30, 2011

Brian H said:
Just enough fuel to get to the closer cylinders i guess....the number 4 cylinder injector is at the end of the injector cluster . I was told it wasnt getting enough fuel pressure to pop the injector. Replaced the engine and it acted the same...replaced the fuel pump and it ran great.

I have never ever seen that.... Not even on a single rail input(returnless)

Brian H · Aug 30, 2011

crash said:
I have never ever seen that.... Not even on a single rail input(returnless)

Thats what the chevy tech said....:scratchhead:Said it needs 52lbs to fire the injectors and it was getting 50 @ idle and 45 @ throttle.

crash2 · Aug 30, 2011

Brian H said:
Thats what the chevy tech said....:scratchhead:Said it needs 52lbs to fire the injectors and it was getting 50 @ idle and 45 @ throttle.

Nope--needs 40psi to blow off the poppets.....

crash2 · Aug 30, 2011

Here is the info straight from GM

An increase in fuel pressure causes the poppet nozzle ball to open from its seat against the extension spring force. This allows the fuel to flow from the nozzle (at approximately 280 kPa (40 psi)).

This is the same for 4.6 v6 be it the CPI or SCPI