Engine/Transmission (1994 - 1998) 47RE early upshift?

[highmilage94]

I have a '97 with a 47re that will start in 1st gear and shift into 3rd gear within 100 feet of movement with normal throttle %. The TC will still lock up on it's own at 30-35 mph. The TPS has 1 volt at idle and the TV cable is adjusted properly. The truck had this problem before the transmission was just rebuilt, so I am assuming the problem is in the truck somewhere. .



It has a new trans speed sensor, but makes no difference if it is hooked up or not. .

It has a Delphi (GM) governor Solenoid.

New valve body.



I'm ridiculously baffled by this, so if someone could help me out, I'd greatly appreciate it... Thanks in advance... .

 

[highmilage94]

'Cmon no one has any input. . ?

TTT

 

[highmilage94]

Hello?? Anyone??

 

[EStarns]

Adjust the cable from the throttle to the transmission. This is how the transmission knows when and how long to hold before shifting. Adjust till there is no slop in the cable.





2001 quad cab long bed 4x4 edge chip and BD brake and guages

2007 6. 7 Red quad cab 4x4 long bed Insight guages.

 

[cerberusiam]

How does it work with 50-75% throttle?

 

[highmilage94]

How does it work with 50-75% throttle?

I'm afraid to try it, to be honest. . It doesn't seem to shift correctly, and being a new trans, I'd rather not chance ruining it. . It seems hesitant to shift at more aggressive throttle %.

TV cable is adjusted properly
TPS has 1v at idle
NEW VB
NEW speed sensor
NEW DELPHI (GM) Governor solenoid
NEW clutches, drums, bands, bearings, output shaft. .

I REPEAT: This truck had the same problem before trans was rebuilt.

If I unplug the Trans Speed Sensor the truck shifts the same as it does if it is plugged in. . This is what I find weird...
Is it possible the governor pressure/temp transducer could cause this?
It is possible I have a broken wire somewhere?
It it possible the PCM is bad? I had the PCM re-flashed May of '08. The truck has sat since then. .

My plan of attack as of now is:
Check for continuity on all 8 wires between the plug and the ECM as well as the speed sensor wires. If nothing is found there, then I will drop the pan and change the Governor pressure/temp transducer. If nothing is found at that point, then I will monitor transmission pressures... If nothing is found as of that point, check the papers. .

 

[cerberusiam]

Off hand it sounds like the TV pressure is low and it sjust skipping 2nd gear. Try tightening the TV cable up tot he max and see if you can influence the shift points.



Trying running 50-75% throttle and check the shifting. That will tell you if its an adjustment or possibly where else to look.



Are you getting any codes? Have you had it scanned with a tool that can read the PCM?

 

[guldam]

My transmission was shifting early before I adjusted the throttle cable. Now it shifts later... Typically it won't shift until 2100 or so rpms. Before it would shift so early that the engine would lug.

I wonder what the typical rpms should be at shift for an unloaded truck with moderate throttle.

GulDam

 

[budnate]

you need to read up on the TPS voltage swing and settings at a given throttle position and check it, and also read up on electrical chatter to and from the TPS, I think your year truck falls into the deal guys were pulling the wire from the loom or installing a resistor at the tps... . get on the search engine lots to read on it.



B.

 

[PToombs]

Are you sure it's not starting in 2nd? It may be in limp mode. After it's moving, try pulling the shifter down into 1 before it upshifts. I drove mine for a few days after I got it before I realised something wasn't quite right. It had a few electrical issues I had to work thru with the trans to get it to work right. Bud helped me with most of it, I figured out the fine tuning of shift points. I have a thread on my problems that will help.

Good luck!

 

[highmilage94]

you need to read up on the TPS voltage swing and settings at a given throttle position and check it, and also read up on electrical chatter to and from the TPS, I think your year truck falls into the deal guys were pulling the wire from the loom or installing a resistor at the tps... . get on the search engine lots to read on it.

B.

Thanks, but I know how to test the TPS voltage and what it should be. . It is fine and my problem has nothing to do with the TPS. With TPS unplugged, the truck still acts the same. .

Are you sure it's not starting in 2nd? It may be in limp mode. After it's moving, try pulling the shifter down into 1 before it upshifts. I drove mine for a few days after I got it before I realised something wasn't quite right. It had a few electrical issues I had to work thru with the trans to get it to work right. Bud helped me with most of it, I figured out the fine tuning of shift points. I have a thread on my problems that will help.
Good luck!

It definitely starts in first, immediately shifts to second, then immediately shifts to third. . I can shift it manually and all three gears are there. .

OK after a few diagnostic tests. . I've come to the conclusion that my Governor pressure is too high. . About 50 psi too high. . This is definitely the problem, I just don't know how to correct it. . I may have a broken wire somewhere...

 

[cerberusiam]

Have you replaced the gov pressure sensor? If it is reading incorrectly the solenoid is setting incorrectly and that will cause the issues.

 

[highmilage94]

Have you replaced the gov pressure sensor? If it is reading incorrectly the solenoid is setting incorrectly and that will cause the issues.

I thought of this as well, but...



Governor pressure is supposed to be:

27-33psi at 30mph



The computer is reading:

60psi at 30mph



A manual gauge in the trans shows:

75-80psi at 30mph

 

[cerberusiam]

I thought of this as well, but...



Governor pressure is supposed to be:

27-33psi at 30mph



The computer is reading:

60psi at 30mph



A manual gauge in the trans shows:

75-80psi at 30mph

It sounds like the gov solenoid is stuck or there is line pressure bleeding into the gov circuit causing the high pressures.



What happens to manual gov pressure if disconnect the trans control harness? If the harness is disconnected the gov pressure should be zero at all times. That might tell you if its a mechanical or electronic issue.

 

[highmilage94]

It sounds like the gov solenoid is stuck or there is line pressure bleeding into the gov circuit causing the high pressures.



What happens to manual gov pressure if disconnect the trans control harness? If the harness is disconnected the gov pressure should be zero at all times. That might tell you if its a mechanical or electronic issue.

If it was a mechanical issue, what could it be?

 

[cerberusiam]

If it was a mechanical issue, what could it be?

VB would be my first guess but since you have a new one that would go to the bottom of the list.



The gov solenoid is another one. The GM solenoids ar eknown for holding the pressure higher and causing hard shifts but what you are seeing means it stuck or something worse.



It really sounds like there is line pressur ebleeding into the gov circuit somehwere. As rare as it is a crack in the case can cause things like this.



Thats the reason I was wondering what the gov pressure did if you remove all the electronic controls. If it stays high and ramps up as rpms go up pretty sure there is a leak from line pressure somewhere. If it stays down zero or real low, then something is telling the solenoid to set it way high.



If you get the same results with harness unhooked between the OE solenoid and the GM solenoid it almost has to be an internal leak.

 

[Allumsr]

i have the same sort of problem in my 95 to 98 model, ive found a few things that made it shift better. i had a vacum issue and ground issuus, tighning the 2 bolts on top front of the intake manifold helped, the 3 wire connecter on the side of the tanny wires were broken. anyway ther is all kinds of things that could be wrong. try shifting it manualy see what happends

 

[guldam]

On my 97, I found that when I got the truck it was pretty anemic on power, and it always shifted just before or at the peak of torque, somewhere around 1. 6k . Then as it shifted, that would drive the rpms too low and the engine lugged.

I fiddled and replaced all sorts of parts and finally discovered the huge amount of play in the throttle cable. I fabricated a part to take out the play, and suddenly the truck had way more power. A side effect is the truck typically shifts from 2k-2. 3k rpms now. That seems a little high now, but I've yet to come across details as to when it should shift.

GulDam

 

[budnate]

2 more suggestions, check the voltage on the orange wired headed to the trans if it has drifted like most of our trucks have it will raise hell with the solanoids in the trans most just fail, yours might be on the ragged edge and not throwing a code yet or burnt them out but giving the solanoids a bad day.....



also I cant find it now but somewhere there is a real good thread on how to tap into the trans ports on the side of the trans and measure the fluid press, it is a very important step most people dont bother to look at.



B.

 

[highmilage94]

VB would be my first guess but since you have a new one that would go to the bottom of the list.



The gov solenoid is another one. The GM solenoids ar eknown for holding the pressure higher and causing hard shifts but what you are seeing means it stuck or something worse.



It really sounds like there is line pressur ebleeding into the gov circuit somehwere. As rare as it is a crack in the case can cause things like this.



Thats the reason I was wondering what the gov pressure did if you remove all the electronic controls. If it stays high and ramps up as rpms go up pretty sure there is a leak from line pressure somewhere. If it stays down zero or real low, then something is telling the solenoid to set it way high.



If you get the same results with harness unhooked between the OE solenoid and the GM solenoid it almost has to be an internal leak.

All tried, everything checks out to be good, except for the gov pressure, lol. . this sucks. .