IP Vacuum Regulator for Automatic Trans?

[turbos10]

Hey all,

I am trying to get my transmission to shift properly and it is not getting vacuum to the modulator. I replaced the vacuum pump, which was bad, but the problem is still the same. The regulator on the IP seems to not be working. This is a manual pump, but the engine is a 96 that was converted, so I dont know if the parts are all correct.

The regulator I have has a couple wires coming out the bottom and going in the harness and then has the two nipples on top. I need to know what the wires on the regulator are for and if they are needed for the regulator. It almost looks to me like a TPS from the original setup, but I am not sure. I also need to know if the regulator is directional; does it matter which hose is plugged where?

Any help is greatly appreciate. Working through someone elses mess is such a pain....

Thanks,

Chris

[Husker 6.5]

Hey all,

I am trying to get my transmission to shift properly and it is not getting vacuum to the modulator. I replaced the vacuum pump, which was bad, but the problem is still the same. The regulator on the IP seems to not be working. This is a manual pump, but the engine is a 96 that was converted, so I dont know if the parts are all correct.

The regulator I have has a couple wires coming out the bottom and going in the harness and then has the two nipples on top. I need to know what the wires on the regulator are for and if they are needed for the regulator. It almost looks to me like a TPS from the original setup, but I am not sure. I also need to know if the regulator is directional; does it matter which hose is plugged where?

Any help is greatly appreciate. Working through someone elses mess is such a pain....

Thanks,

Chris

The vacuum pump's ONLY function is to supply vacuum to the wastegate control solenoid and the two EGR solenoids (if equipped). The two wires coming out the bottom are for control input from the ECM to open and close the solenoid. One port is vacuum source (the vented one), the other goes to the device being controlled (wastegate controller or EGR valve).

These control solenoid(s) are mounted on a bar on the back part of the driver's side intake manifold. If what you are describing is part of the IP, then if it is on the front (towards the radiator) it is the fuel shut off solenoid, and if it is on the back of the pump, it is for the stepper motor. This is for the electronic IP found on the stock 96 motor.

The 4L80E (E is for electronic) transmission is controlled by computer for all its shifting programming.

Hope this helps.

Husker 6.5:)

[sixnickel]

What transmission? 4L80E 4sp O/D or 3L80( turbo 400 )3sp.

[turbos10]

Sorry, I failed to mention this is in an 87 GMC that was originally 6.2 equiped. The transmission is a TH400(diesel version is a different number I think) and the regulator on the IP goes to the modulator on the transmission to mimic a gasoline engine from what I understand. The transmission does also have a single wire hookup that is unhooked. I am thinking this may be a kickdown, but I dont know for sure. I am just not familiar with these diesels(yet).

I posted about this before and got a site for a cable modulator. If I had been thinking when I found out the pump had failed I would have bought one of them, but I had a king size brain fart and replaced the vacuum pump instead....so, I need to try to get it working with this regulator.

[grancito]

Sounds like you have a buggers muddle there. The basic transmission types were not different for diesels but they had some small mods, like governor, for change speeds and maybe valve body plate mod. and of course a different torque convertor.The loose wire is probably for the torque convertor clutch. From there I'm out of my depth because I don't know if GM went back to vacuum control after the TH700R4, which is cable controlled like many other much later transmissions in other makes. I think NJDEVILL had a TH400 in his vehicle, let´s see if he replies.

[Husker 6.5]

Sorry, I failed to mention this is in an 87 GMC that was originally 6.2 equiped. The transmission is a TH400(diesel version is a different number I think) and the regulator on the IP goes to the modulator on the transmission to mimic a gasoline engine from what I understand. The transmission does also have a single wire hookup that is unhooked. I am thinking this may be a kickdown, but I dont know for sure. I am just not familiar with these diesels(yet).

I posted about this before and got a site for a cable modulator. If I had been thinking when I found out the pump had failed I would have bought one of them, but I had a king size brain fart and replaced the vacuum pump instead....so, I need to try to get it working with this regulator.

AHH... TH400. That's more up my old school alley, I had a TH400 behind my big block 72 Monte in high school. Anyway, unlike the TH350 and 700R4, which use mechanical input, that wire is indeed your "kickdown" and receives its input signal from a switch that would mount in front of your throttle crank on a Q-Jet, when you went full throttle it would depress the switch, and if the modulator would allow, kick you down into second gear. The IP off your 6.2 has everything you need to hook up (if you still have it) and should swap over to your DB-2 mechanical pump.

Help me out on this one Doug (sixnickel), you have tons of expertise with 6.2's.

Husker 6.5

[turbos10]

AHH... TH400. That's more up my old school alley, I had a TH400 behind my big block 72 Monte in high school. Anyway, unlike the TH350 and 700R4, which use mechanical input, that wire is indeed your "kickdown" and receives its input signal from a switch that would mount in front of your throttle crank on a Q-Jet, when you went full throttle it would depress the switch, and if the modulator would allow, kick you down into second gear. The IP off your 6.2 has everything you need to hook up (if you still have it) and should swap over to your DB-2 mechanical pump.

Help me out on this one Doug (sixnickel), you have tons of expertise with 6.2's.

Husker 6.5

Okay, thanks for confirming on the kickdown. Unfortunately I did not do the engine swap so I inherited another guys mess when I bought the truck. I gave up and took it to a shop today to have them look at it. They got vacuum to the modulator, but everything is out of whack so they are going to get it tuned back in. They think there is also a governor problem which I had been told before, so they are looking into that. They also confirmed suspicion that there was a leak between the transfer case and transmission, so they are dropping the transfer case to fix it.

Swaps like this that are not done right to start just suck to fix. One thing at a time and I will get it there.

[Husker 6.5]

Okay, thanks for confirming on the kickdown. Unfortunately I did not do the engine swap so I inherited another guys mess when I bought the truck. I gave up and took it to a shop today to have them look at it. They got vacuum to the modulator, but everything is out of whack so they are going to get it tuned back in. They think there is also a governor problem which I had been told before, so they are looking into that. They also confirmed suspicion that there was a leak between the transfer case and transmission, so they are dropping the transfer case to fix it.

Swaps like this that are not done right to start just suck to fix. One thing at a time and I will get it there.

Oh yeah, I used to make really good money as a finish carpenter/remodel contractor going in and doing right some abomination that was a homeowner's easy do-it-yourself project. Never failed, they thought they knew what they were doing until they suddenly realized way too late that they didn't.

Same thing at work, now. I really hate putting back together a piece of equipment that someone off first or second shift took apart, no telling what they were doing, or what they thought was wrong.

Husker 6.5

[njdevi11]

Ive got a th400 in my jeep, I suggested the cable modulator earlier. It seems like the most robust fix to this problem, thats what the military uses. The wire is a kickdown switch and as far as I know a th400 doesn't do lockup. You can put a switch under your accelerator pedal to make it kick down or get a button to put on the dash to kick it into second gear. For stuff like this, the only suggestion I have is guess and check. Plug the hoses in one way if that doesn't work right try it the other. Get a test light and see if any of those wires switch on when you go WOT.

I'm converting my TH400 to an SM465 this weekend actually, the auto is out. Right now to get my th400 to shift i ran a tube from the modulator into the cab so I can suck on it when I want it to shift. Another solution to getting this thing to shift correctly I was considering is to get a reprogramming kit so I can shift it manually (you guys have to remember this is an off road rig not a DD).

Maybe one day I'll find a good price on a th400 np205 or a doubler setup (an np203 gear reduction box mated to an np205 for 2 x the 4 low) and convert back, but until then I'm a standard shift kinda guy. I really have to see how my rig handles rocks and crawling.

[turbos10]

I got the truck back from the shop today after $225. Turns out that the previous idiot bent the kick down valve on the valve body and put in two gaskets to try to fix or something. It was loosing pressure there and was similiar to being in kickdown mode all the time.

They also found that the transfer case was full of ATF due to a bad seal so they dropped it and replaced the seal.

The truck runs and drives very nice now; varied shifts, kickdown, and holds gears perfectly.

NJD, that rock crawler will probably be a bear to handle with a standard. I have to say, now that setup the TH400 seems nice.

Thanks for all the suggestions guys. This one ended up being a fluke.