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Username Post: 1999 z71 transmission        (Topic#262704)
sprog777 
Forum Newbie
Posts: 31

Reg: 03-27-10
05-09-11 02:09 PM - Post#2087886    

When i gradually go up a hill and its time for the automatic transmission to downshift it makes a thump and shakes the truck like it dosen't go into gear but if i tromp down on gas it shifts down ok anyone have an idea? I was told by phone it was an electrical problem.
sprog777@yahoo.com

1979 K5 Blazer
1995 Chevy S-10
1999 Chevy Tahoe 4wd
1999 chevy z71 ext.cab


 
Low priced Genuine GM Auto Parts
CaptainK 
Senior Member
Posts: 8242
CaptainK
Loc: Maryland
Reg: 02-25-02
05-11-11 04:23 AM - Post#2088509    
    In response to sprog777

If you have the 4l60e tranny, these are known to have a 2nd - 3rd upshift and a 3rd - 2nd downshift clunk. Generally the heavier you are on the gas pedal the less noticable it is.
'99 Silverado (NBS)


 
sprog777 
Forum Newbie
Posts: 31

Reg: 03-27-10
05-11-11 01:05 PM - Post#2088747    
    In response to CaptainK

the transmission dosen't just clunk it dosen't down shift properly and the truck shakes like it is lost as what gear to be in.But when i give it a lot of gas it goes ahead and downshifts.
sprog777@yahoo.com

1979 K5 Blazer
1995 Chevy S-10
1999 Chevy Tahoe 4wd
1999 chevy z71 ext.cab


 
Bad Bowtie 
Valued Contributor
Posts: 4543
Bad Bowtie
Age: 42
Loc: TX
Reg: 07-04-03
05-11-11 01:39 PM - Post#2088761    
    In response to sprog777

Sounds like a bad valve body. They had a few problems with the early ones...
GMC. We are Professional Grade.

http://www.cardomain.com/id/2004VHO


 
transman618 
Senior Member
Posts: 839
transman618
Loc: Cumming,GA
Reg: 06-06-04
05-15-11 06:23 AM - Post#2090250    
    In response to sprog777

Sounds like a bad TPS or even a drivability issue. (Plugs, coils etc..) Time to get a scanner on it and monitor the live data.


transman
GM MASTER TECHNICIAN
SR. TRANSMISSION BUILDER



Edited by transman618 on 05-15-11 06:24 AM. Reason for edit: No reason given.

 
sprog777 
Forum Newbie
Posts: 31

Reg: 03-27-10
05-22-11 01:22 PM - Post#2093536    
    In response to transman618

not familar with tps scanned for codes none for misfires it is a transmission problem.Is that valve body internal.noticed some valves outside transmission on right side.
sprog777@yahoo.com

1979 K5 Blazer
1995 Chevy S-10
1999 Chevy Tahoe 4wd
1999 chevy z71 ext.cab


 
transman618 
Senior Member
Posts: 839
transman618
Loc: Cumming,GA
Reg: 06-06-04
05-23-11 05:53 PM - Post#2094096    
    In response to sprog777

TPS (Throttle Position Sensor). The computer uses information from the TPS to control shifting in the transmission. This is where I would start. Read the live data coming from the TPS, just because there was no code does not mean the TPS is good. That scanner, when used properly will rule out any electronic issues and tell you whether the transmission needs to come apart to be repaired. You need to use the scanner and see whether the computer is commanding the shifting.
You blew off my response when I told you to check the TPS, you said that it IS a transmission problem. Can I ask how you arrived at this??


transman
GM MASTER TECHNICIAN
SR. TRANSMISSION BUILDER



 
sprog777 
Forum Newbie
Posts: 31

Reg: 03-27-10
07-22-11 12:44 PM - Post#2116839    
    In response to transman618

I did not understand that you where speaking of the tps throttle position sensor.Wasn't trying to say that you did not know what you where talking about.Anyway the problem has gotten worse. It does it a lot more now. One more thing i observed is when it is trying to make up its mind as what gear to be in I can press the tow/haul switch and it goes ahead and downshifs.
sprog777@yahoo.com

1979 K5 Blazer
1995 Chevy S-10
1999 Chevy Tahoe 4wd
1999 chevy z71 ext.cab


 
sprog777 
Forum Newbie
Posts: 31

Reg: 03-27-10
09-24-11 09:19 PM - Post#2140473    
    In response to sprog777

well it wasn't the tps.Changed plugs and wires and it drives like a new one.Wow who would of thought.Less than a 100 bucks and drives like a new truck.
sprog777@yahoo.com

1979 K5 Blazer
1995 Chevy S-10
1999 Chevy Tahoe 4wd
1999 chevy z71 ext.cab


 
Low priced Genuine GM Auto Parts
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