4l80 swap clarifying questions

[erasedhammer]

I am installing a 4l80 soon but I have a few clarifying questions before I begin.

1. Where is the TPS located? On the IP or the gas pedal?
2. If it's on the IP can the TPS be mounted on a 6.2l injector pump?
3. If it cannot or requires modifications is there a civi counterpart to the TPS that will mount directly to a 6.2 IP? Plug and play style?

4. The tutorial posted on g503 references the need for a fan cutout switch bracket and linkage ? What is this for and is it required?

5. I was thinking of using the rpm sensor that's already installed and appears to be hooked up to the diagnostics connector, but I read that it can't be used because it has the wrong revs? If I can't use that and I am attempting to use a a2 harness with the 6.2 what do you guys suggest I use to supply engine speed to the transmission. I have a tach setup using the alternator, I assume that it cannot be used either?
6. I was looking at the wiring diagram for the a2 body harness, and it is unclear what connector I would plug the engine speed output into, as I think the digram assumes I would be using the matching engine harness (I hope I won't have to?)

6.5: I assume that the tcm's 12v is drawn from one of the two batteries and then it is hooked up to a circuit breaker and then a relay so only when the ignition is on run position does the TCM recieve power? Or is the 12v connector hooked directly to the 12v tap on the alternator?

7. Exactly how much longer is the 4l80 than the 3l80? Some places I've heard an inch others Ive heard 6 inches.

8. The transmission cross member. I've heard from some people on bay that the cross member is exactly the same and can be reused for the 4l80, and all it needs is to be mounted a little bit further back on the frame. I did get the replacement mounting piece as the post on g503 said it would be good to replace it.

9. Do I need a speed sensor somewhere on the output side of the transmission or does it take that data from the speedometer sensor on the t/c?

I don't think I'm missing anything, but if anyone thinks I am, please do bring it up. If I've learned anything it's to plan each project out as much as possible to make things go as smooth as possible.






Driveshafts that I have installed:

 

[beckel]

See Below...

I am installing a 4l80 soon but I have a few clarifying questions before I begin.

1. Where is the TPS located? On the IP or the gas pedal? The TPS is located on the 6.5L injection pump. 6.2L IP's do not have the correct TPS driver pin. my opinion..do yourself a huge favor and go with a US Shift aftermarket controller and a EZ TCU standalone cable driven TPS.
2. If it's on the IP can the TPS be mounted on a 6.2l injector pump? No. see above.
3. If it cannot or requires modifications is there a civi counterpart to the TPS that will mount directly to a 6.2 IP? Plug and play style?

4. The tutorial posted on g503 references the need for a fan cutout switch bracket and linkage ? What is this for and is it required? If you use the EZ TCU remote TPS you dont need to change your 6.2L fan cutout (Its mounted on the 6.2L IP)

5. I was thinking of using the rpm sensor that's already installed and appears to be hooked up to the diagnostics connector, but I read that it can't be used because it has the wrong revs? If I can't use that and I am attempting to use a a2 harness with the 6.2 what do you guys suggest I use to supply engine speed to the transmission. I have a tach setup using the alternator, I assume that it cannot be used either? You need a dakota digital interface to convert the analog sawtooth signal from the oil pump drive to a digital RPM signal.
6. I was looking at the wiring diagram for the a2 body harness, and it is unclear what connector I would plug the engine speed output into, as I think the digram assumes I would be using the matching engine harness (I hope I won't have to?)

6.5: I assume that the tcm's 12v is drawn from one of the two batteries and then it is hooked up to a circuit breaker and then a relay so only when the ignition is on run position does the TCM recieve power? Or is the 12v connector hooked directly to the 12v tap on the alternator? Correct, the military relay is $50 on epay. Use this to pass 12v to your US Shift controller. Beware that if you do not have a dual voltage alternator then you will see a slight differential in battery drain. you will need to periodically top off your 12v battery.

7. Exactly how much longer is the 4l80 than the 3l80? Some places I've heard an inch others Ive heard 6 inches. Exactly 2 inches on each driveshaft. One gets cut down 2 inches and one gets extended 2 inches

8. The transmission cross member. I've heard from some people on bay that the cross member is exactly the same and can be reused for the 4l80, and all it needs is to be mounted a little bit further back on the frame. I did get the replacement mounting piece as the post on g503 said it would be good to replace it. The crossmember has to be replaced. The new one sits 2 inches further back than the original. $150 on epay.

9. Do I need a speed sensor somewhere on the output side of the transmission or does it take that data from the speedometer sensor on the t/c?The US shift contorller will tap both the input speed sensor and output speed sensors already present on the 4L80E

I don't think I'm missing anything, but if anyone thinks I am, please do bring it up. If I've learned anything it's to plan each project out as much as possible to make things go as smooth as possible.

 

[erasedhammer]

See Below...

1. The TPS is located on the 6.5L injection pump. 6.2L IP's do not have the correct TPS driver pin. my opinion..do yourself a huge favor and go with a US Shift aftermarket controller and a EZ TCU standalone cable driven TPS. Well I would prefer to stick with the original military configuration of an a2 vehicle. I do go fording a lot, and I find myself going too fast on trails with washboard, so durability is also a concern. So I'm not sure that a aftermarket controller would fit my needs, plus from what you said, I am only missing the fan clutch, and the ess, I have all the other parts already, including the military tcm, and I have a body harness on backorder.
4. If you use the EZ TCU remote TPS you dont need to change your 6.2L fan cutout (Its mounted on the 6.2L IP) Assuming I don't use the aftermarket controller, what tps should I use? Obviously people with 6.2s have done this, so I wonder what they did. I know that there are some chevy gm 6.2l tps's, is the injector pump different on other gm 6.2s?
5. You need a dakota digital interface to convert the analog sawtooth signal from the oil pump drive to a digital RPM signal. So the oil pump drive is the only way to give a engine speed to the tcm, regardless if its military or civi? But I assume I still need to convert the analog signal to digital then feed it to the tcm, which I also assume can be done and fed to the military tcm. Are there any other options for supplying engine speed? Could an a/c signal, like the one used in the newer tachometers, be used to feed the military tcm?
6.5: Correct, the military relay is $50 on epay. Use this to pass 12v to your US Shift controller. Beware that if you do not have a dual voltage alternator then you will see a slight differential in battery drain. you will need to periodically top off your 12v battery. all good there
7One gets cut down 2 inches and one gets extended 2 inches So an extension of 2 inches
8. The transmission cross member. I've heard from some people on bay that the cross member is exactly the same and can be reused for the 4l80, and all it needs is to be mounted a little bit further back on the frame. I did get the replacement mounting piece as the post on g503 said it would be good to replace it. The crossmember has to be replaced. The new one sits 2 inches further back than the original. $150 on epay. Arent the two cross members the same? just mounted in the different locations? Couldn't you take the existing cross member and move it 2 inches aftward, then remount it to the frame?
9. Do I need a speed sensor somewhere on the output side of the transmission or does it take that data from the speedometer sensor on the t/c?The US shift contorller will tap both the input speed sensor and output speed sensors already present on the 4L80E So with the military tcm, where does it get the output speed? And where do I get the sender.

m

 

[Augi]

Hmmm... There is some good information and a bit of mis-information above...

The TPS is located on the injection pump, but the 6.5 turbo pump has a smaller throttle shaft than the 6.2/6.5 NA pumps. The military turbo TPS will not fit onto the NA shaft, but the civilian TPS will. The TPS's are identical electrically they just have different housings. The Civvy TPS has the connector at the end of a short pigtail and the military one has the connector molded into the housing (they use the same automotive style connector). I wouldn't worry about a durability difference between the two, they are the same thing just different form factors.

The fan cutout switch is actuated when you floor the gas pedal and disengages the fan so the blades don't break when fording. The switch is mounted where the TPS needs to go, so you have to remove it and relocate it. There is a bracket that is used on the turbo and A2 trucks for doing this.

The engine speed sensor running off of the oil pump drive runs at cam speed (1/2 crank speed) so it is not usable. I believe there is a part that was used on one year of Chevy van that had double the pulse output so it could run at half speed and give the correct signal. You'll have to do some research to find it though. I believe that one will hook right up to the trans computer without an interface board like the Dakota Digital.

The factory location for the sensor is in a bung on the timing cover of the engine. The 6.5 timing cover with the bung will fit on the 6.2 engine. You'll also have to install the pinwheel on the crank to trip the sensor. It's got four little tabs on it.

If you don't install the speed sensor, the trans warning light will always be lit (assuming you install one) and the torque converter will never lock up.

There are various versions of body and engine harnesses, and it is possible that you will have to get an A2 engine harness. I think there was one version of harnesses where the RPM sensor connector was on the engine harness and one version where it was on the body harness. The 6.2 engine harness obviously doesn't have the connector.

I can't remember exactly how much longer the transmission is, but 2" sounds about right. What you care are about is where the transfer case ends up. You'll need a new drive shaft regardless and if you have rear caliper parking brakes then you don't have to modify it anyway. It'll all just bolt up.

The frame rails have mounts bolted on for the transmission crossmember, but they are very difficult to move because you don't want to drill the rails. What they did at the factory instead was to weld a tab onto the crossmember to put the mount further rearward. You'll need to find one of those crossmembers.

Finally, the military trans computer only looks at the input speed sensor. You can have the output sensor disconnected and it will work fine. It doesn't know vehicle speed at all, just engine speed and trans input speed.



Augi

 

[erasedhammer]

Hmmm... There is some good information and a bit of mis-information above...

The TPS is located on the injection pump, but the 6.5 turbo pump has a smaller throttle shaft than the 6.2/6.5 NA pumps. The military turbo TPS will not fit onto the NA shaft, but the civilian TPS will. The TPS's are identical electrically they just have different housings. The Civvy TPS has the connector at the end of a short pigtail and the military one has the connector molded into the housing (they use the same automotive style connector). I wouldn't worry about a durability difference between the two, they are the same thing just different form factors.

The fan cutout switch is actuated when you floor the gas pedal and disengages the fan so the blades don't break when fording. The switch is mounted where the TPS needs to go, so you have to remove it and relocate it. There is a bracket that is used on the turbo and A2 trucks for doing this.

The engine speed sensor running off of the oil pump drive runs at cam speed (1/2 crank speed) so it is not usable. I believe there is a part that was used on one year of Chevy van that had double the pulse output so it could run at half speed and give the correct signal. You'll have to do some research to find it though. I believe that one will hook right up to the trans computer without an interface board like the Dakota Digital.

The factory location for the sensor is in a bung on the timing cover of the engine. The 6.5 timing cover with the bung will fit on the 6.2 engine. You'll also have to install the pinwheel on the crank to trip the sensor. It's got four little tabs on it.

If you don't install the speed sensor, the trans warning light will always be lit (assuming you install one) and the torque converter will never lock up.

There are various versions of body and engine harnesses, and it is possible that you will have to get an A2 engine harness. I think there was one version of harnesses where the RPM sensor connector was on the engine harness and one version where it was on the body harness. The 6.2 engine harness obviously doesn't have the connector.

I can't remember exactly how much longer the transmission is, but 2" sounds about right. What you care are about is where the transfer case ends up. You'll need a new drive shaft regardless and if you have rear caliper parking brakes then you don't have to modify it anyway. It'll all just bolt up.

The frame rails have welded mounts for the transmission crossmember, so they are very difficult to move. What they did at the factory instead was to weld a tab onto the crossmember to put the mount further rearward. You'll need to find one of those crossmembers.

Finally, the military trans computer only looks at the input speed sensor. You can have the output sensor disconnected and it will work fine. It doesn't know vehicle speed at all, just engine speed and trans input speed.



Augi

So I can get a civi TPS and it will work with the 6.2 IP? I assume there is only a specific one that works, like a Chevy GM 6.2l TPS perhaps?

And as for the engine speed, I see rpm sender units that plug in to that location all over epay. So I could take one of those and assuming that I find a 6.5 sender then I should be fine? My vehicle came with what looks like one already installed and wired up. Idk if it's a dud or purely a diagnostic tool, it's top is yellow if that helps.

I do have the rear caliper brakes and I think that when the t/c is two inches back I'll still have clearance around it for the fuel tank and muffler. I'm glad I don't have the 218.

Do you know if there are any of those cross members specific to the 4l80 being sold on epay at the moment? Ive seen plenty but all the sellers don't know the difference or they tell me there is no difference.

Thanks for the clarification, it seems that acquiring the right parts just got a lot simpler.

 

[Augi]

Have you read my trans swap post? It's a sticky at the top of this section. It has the TPS p/n and even a picture.

I don't believe the eBay speed sensors will work, but you can try. I can't remember how to tell the difference. I think a 94 H1 had the sensor you need also. Check the parts book if you can find one. The one you have installed definitely won't work.

The 4l80 crossmember is pn 12447053 and there is one on eBay. You can see it has an extra tab the others don't.

Augi

 

[erasedhammer]

Have you read my trans swap post? It's a sticky at the top of this section. It has the TPS p/n and even a picture.

I don't believe the eBay speed sensors will work, but you can try. I can't remember how to tell the difference. I think a 94 H1 had the sensor you need also. Check the parts book if you can find one. The one you have installed definitely won't work.

The 4l80 crossmember is pn 12447053 and there is one on eBay. You can see it has an extra tab the others don't.

Augi

I found the TPS.
Do you happen to have the manual page number or the nsn fan clutch bracket and linkage?

Also, where could I get the rear drive shaft assembly. I am currently watching the correct front drive shaft on epay but the rear shafts listed there do not have nsns so I have no way of verifying if it's the correct shaft.

 

[erasedhammer]

Looks like I found the correct rpm sensor to feed the TCM. It was relatively easy to find and plenty of websites are selling he 94-98 oil pump drive speed sensors.

It costs an arm and a leg for such a small sender, $400.

 

[86humv]

I found the TPS.
Do you happen to have the manual page number or the nsn fan clutch bracket and linkage?

Also, where could I get the rear drive shaft assembly. I am currently watching the correct front drive shaft on epay but the rear shafts listed there do not have nsns so I have no way of verifying if it's the correct shaft.

I have all the sensors and switches and brackets off 6.5 NA motors.
Rear drive shafts depend on what diff. yoke you have.....there are 3 different ones, and two different front diff. yokes.

 

[erasedhammer]

I have all the sensors and switches and brackets off 6.5 NA motors.
Rear drive shafts depend on what diff. yoke you have.....there are 3 different ones, and two different front diff. yokes.

How do I find out what yoke I have? And once I do, I've looked at the parts manual and the diagram that is there is not clear as to what transmission it will fit. It gives three different fferent nsn for the t/c but it doesn't give the respective drive shaft for each different yoke.

 

[86humv]

Here's some of the components off a 6.5NA 4L80e assembly :


Injection pump with red circle is a 6.5NA A2 pump
Circled with yellow is a 6.2, 6.5 de-tuned A0-A1 pump.