• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

4L80E No Power - Recent Engine Swap

I just got home. Shut the truck off and about 10 minutes later I checked the fluid level...it was maybe half a inch above the box marked hot ..I started the truck and checked again it was at top of the box marked hot...so it only dropped about half a inch running...keep in mind the engine was already hot for both measurements..don't know if that makes a difference in this test...but TheFerm said it should drop couple inchs I believe. Soooo.
 
Needless to say, life has been hectic as we're general contracting our own house, raising a three year old, down to one vehicle, and working a full time gig, whilst in the reserves, whilst getting an exemption...great experience, don't want to do it again! I have been unable to post what's happened, and things have DEFINITELY happened.

I'll keep it to bullet points as there is a lot and summarize at the end with the SOS.

Part 1
- Drained the fluid, changed the internal harness (realized I didn't have the right hex nuts and had to leave the solenoids in)
- Filled trans back up, started. Shifted between the gears a while to lube it up.
- Truck actually began shifting and driving. Managed to get through all gears. Drove it home and celebrated...too soon.

Part 2
- Next day drove to property, 10 miles away the RPMs shot up, trans fluid burning smell, still had OD but it was acting like I was in limp-home mode.
- Cooled off, slowly drove it to my property as I knew it would have to sit a while.
- At property, parked and let it idle. Fought reverse like crazy, popping and clunking (had to get it back to a position for flatbed)
- Would go into D (not OD). Fought reverse every time.
- Once the transmission shop (as this was clearly over my head in) could take it, towed it to shop.

Part 3
- Nationwide Transmission digs into the trans and finds belts worn, also finds it's a remanned Monster transmission (none of us know how it lasted 6 years, sorcery), recommends full rebuilding internal. I agree and upgrade to billet aluminum.
- Trans shop calls me and tells me that "it's shifting between gears now after build, but stalls and shuts off at stops. Restarts fine and drives fine, but again shuts off at lights. Related to torque converter."
- A big issue, they never figured out how to communicate with my computer even after talking with a Hummer tech I gave them the number for.
- Rebuild again.
- Still shuts off at stops. They recommend complete rebuild with new housing, do it.
- Rebuild everything.
- They say it's good, take it home and drive it until you believe it's good and then we'll worry about payment. If it doesn't work, it's free and we can't fix it.
- ...and 10 miles from my property, RPMs go up, no reverse (or randomly very little).

Part 4
- Towed to home, I'm doing it now.
- Repeatedly I tried the paperclip method and got the default, code 12 "everything's fine", code.
- Began hunting for anything out of place and tons of phone calls.
- All fuses checked and rechecked (going to check again), all connections checked.
- I decide to start the truck for the sake of keeping the batteries charged. Decide to check the codes while it's running.
- GET A CODE: Code 71. It means "Cam Position Engine Speed Sensor signal not detected "
- Crankshaft sensor was never plugged in on build and I never thought to look.
- Talking with friend/tech, he confirms turbo trucks don't have camshaft sensor, but crankshaft.
- I re-wire my old tachometer pigtail (which was just hanging out) to the crankshaft), transmission light goes off for first time.

Part 5
- Truck starts rough but now idles smooth after initial start.
- Truck still does not like engaging reverse or over drive, but will engage in D, 2, and 1.
- Sometimes it will engage in Reverse, but does not have much power.
- I have been hunting for bad grounds and have not found any yet, last place to check is driver kick panel, I'm guessing it's fine.
- Trying to get a well known diesel shop nearby to send a mechanic with a Tech2 to scan my truck and look it over pretty well for anything that stands out. We shall see how that goes as it would be extremely informative.

This leads me to questions I have been pondering.
1) Old 6.5 NA trucks had a camshaft sensor, turbo diesel trucks do not...but, I found one blurb reading that turbo diesel trucks actually have a camshaft sensor built into the injection pump. Guess what, I have a Stanadyne DB2 old school pump. Is this a problem on a mechanical turbo though?
2) Wiring the old tachometer plug to the crankshaft sensor shut off the light and now has the truck idling better, BUT, will this cause a problem long term (other than I need proper wiring so it's not picking up the engine rotation).
3) I'm wondering if I don't actually have a geared hub or Tcase seizing, acting like a brake. I have one hub that I suspect. Obviously, my schedule makes this difficult to do right away, but I will be jacking up the truck and checking for rotation or lack-thereof. Could this cause all the transmission woes?
4) To me, this seems like it's something that no one has thought of yet, and it's just waiting to be discovered. A neon orange needle in a haystack that, once discovered, we'll all go "well of course that's the problem!". Does anything stand out?
5) My one Hummer tech thinks I need a M1165 injection pump (modified for 12 volt) instead of my DB2. Do I need to do this or am I fine with DB2 (as another Hummer tech says I don't).


Going Star Wars on you - Help me @THEFERMANATOR ,you and the forum gearheads are my only hope.

I'm out of ideas, really desperate to get my second vehicle more useful than being an interesting-looking paperweight that makes noise. You have no idea how much this would help my family getting it rolling again. Any ideas and advice is valuable and I am grateful for it.

-CJ
 
Last edited:
@cander27 sitt tight it's been slow on here today...just a dumb hunch... Have you changed the crank position sensor or the temp sensor that's up by the thermostat housing?? A/c Delco ones of course... I'm asking cause my truck solved alot of problems by changing them.. the fact that pig tailing into the crank sensor effected it tells me your on the right track.. could be that by pigtails it the way you did made something get a better connection..if I remember right there's only 2 wires to each sensor..so if the sensor is bad or one of the wires has a short in it somewhere it may be making just enough of a better connection to shut the light off and make it runn a little better.... Maybe try getting under it where you can get to the wires with somebody you trust at the wheel and try moving those wires around maybe with a screwdriver or something to keep your hand out of the pulleys, and I have them watch to see if the light goes on and off if you seriously trust them you can have them try shifting it into reverse and see what happens.. please keep in mind I am nowhere near as experienced as the other guys on here especially when it comes to a transmission issue cuz I've been having my own.. hear so please wait until Terminator or one of the other guys chimes in to double-check my thinking..
 
The cranking shaft position sensor and the coolant temp sensord thats in the thermostat housing are two items that are not expensive. You might pick up one of each, replace the old ones and see what the unit does.
 
Ok, let me step in here a minute.
The 95 was originally non turbo, uses db2 ip, ESS (engine speed sensor) on the oil pump drive. That ESS feeds both the tachometer and the TCM- Transmission Control Module.

THE SUPER 77 turbo he is referring to is either a gm6 or gm7 center mount mount turbo with a wickedwheel in it. To fit the center mount turbo, you have to remove the ESS and use a plain oil pump drive. This leads to the issue I ran into adding my turbo- controlling the TCM. The ESS is a 2 wire sensor. The db2 timing gears do not have the 4 point unit kn the crank shaft for the CPS (crankshaft position sensor) to work. If you get the one from a ds4 equipped engine, it has it. But ds4 engine comes with a 3 wire CPS

So I went to a junkyard and found one close enough to work from a mazda/ford engine and modified it. But later learned the better answer is order the CPS for a newer turbo equipped hmmwv- because it is a 2 wire sensor!!!

So @cander27 After all that mess... What EXACTLY do you have for the sensor?
This could be the whole dang problem.
 
Will L. said:
Ok, let me step in here a minute.
The 95 was originally non turbo, uses db2 ip, ESS (engine speed sensor) on the oil pump drive. That ESS feeds both the tachometer and the TCM- Transmission Control Module.

THE SUPER 77 turbo he is referring to is either a gm6 or gm7 center mount mount turbo with a wickedwheel in it. To fit the center mount turbo, you have to remove the ESS and use a plain oil pump drive. This leads to the issue I ran into adding my turbo- controlling the TCM. The ESS is a 2 wire sensor. The db2 timing gears do not have the 4 point unit kn the crank shaft for the CPS (crankshaft position sensor) to work. If you get the one from a ds4 equipped engine, it has it. But ds4 engine comes with a 3 wire CPS

So I went to a junkyard and found one close enough to work from a mazda/ford engine and modified it. But later learned the better answer is order the CPS for a newer turbo equipped hmmwv- because it is a 2 wire sensor!!!

So @cander27 After all that mess... What EXACTLY do you have for the sensor?
This could be the whole dang problem.
Click to expand...

HOLY SMOKES BATMAN!

I didn't realize on the HML and here that you had a 95 and added a turbo and therefor have pretty much the same setup...and had the same problems! Well you're the man to talk to as it sounds like you had the exact same issue.

I do not have an ESS/camshaft sensor (If I'm getting that right) as there is no room at the back of the engine, yes. Clearly, that immediately points to the problem of not feeding info to the tach (fixed that), and WAY more importantly, the TCM. I have the old DB2.

The only sensor I have right now is an M1165 (HMMWV) crankshaft sensor behind the harmonic balancer, driver side. This was put in at GEP factory. I re-wired and plugged in the old pigtail tachometer plug to that. Trans light went away, idles better. But still not happy shifting (I believe the crankshaft sensor rotates faster than the camshaft sensor did?). Does that make sense or do you want me to break it down more, I know it's all extremely complicated due to the build.

*Edit, boy I feel dumb, "Crankshaft Position Sensor (CPS)", duh. But now I'm confused since I have one. How did you wire yours?

I can't tell you how happy I am right now!
 
Last edited:
There is a part that has to be inside the timing cover for that sensor to work. Called a RELUCTOR. You need to know you have one in there. This is the crankshaft timing gear. The reluctor is the 4 pointed item on the front of it. They do not come on the timing sets for db2 engines.

BD4145BF-A04F-462A-8F96-678637EB84AC.png
 
I don’t know if removing the CPS you could rotate the engine with a flywheel turner and see (tell) there is one in there or not.

also, if there is one in there- are you getting signal to the TCM-broken wire somewhere?
Double check where you extended them.

Afaik there is no difference which way the wires are hooked up: no polarity. But maybe there is?
 
Will L. said:
There is a part that has to be inside the timing cover for that sensor to work. Called a RELUCTOR. You need to know you have one in there. This is the crankshaft timing gear. The reluctor is the 4 pointed item on the front of it. They do not come on the timing sets for db2 engines.

View attachment 69192
Click to expand...

Interesting. So the Reluctor would make the crankshaft sensor work with the DB2 setup, then my TCM would finally be happy? I'm guessing since my engine was setup intended for a turbo, and they were thinking DS4 or something else, that this gear is not in my truck?

Now that I actually have terms I can search for I popped up some info, let me run it by you out of curiosity:

Apparently the ESS/camshaft sensor signal on the old 6.5 NA was analog. The signal from the Crankshaft sensor is digital. That's why just swapping the wiring only partially worked (killed the trans light) but it still isn't giving the right info to the TCM, it's not 100% compatible.

HMMWV's get their ESS from the tcase speed sensor / ring tone? Does that mean it's possible to wire up to the Tcase (I have no idea, which is why I'm asking...especially since that would be way, way more simple than pulling the timing cover off, ha!)
 
Forget transfer case. Wrong item.
I searched so many options and they all create different problems.

You have a 50/50 chance your timing gear has the reluctor on it. You need to verify yours has it.

Does your CPS —ON THERE NOW HAVE 3 wires or 2?
 
Will L. said:
I don’t know if removing the CPS you could rotate the engine with a flywheel turner and see (tell) there is one in there or not.

also, if there is one in there- are you getting signal to the TCM-broken wire somewhere?
Double check where you extended them.

Afaik there is no difference which way the wires are hooked up: no polarity. But maybe there is?
Click to expand...

Will L. said:
Forget transfer case. Wrong item.
I searched so many options and they all create different problems.

You have a 50/50 chance your timing gear has the reluctor on it. You need to verify yours has it.

Does your CPS —ON THERE NOW HAVE 3 wires or 2?
Click to expand...

2 wires.

I'll double check that there isn't a loose connection. Since the trans light went out once I plugged it in there is definitely some amount of communication, but clearly it's still not 100%, and with my DB2 (and they probably assumed it was DS4) it makes me think it's not compatible.

I should be able to find out with a couple calls tomorrow if there is a reluctor as it was assembled new and tested before being shipped to me. That would be the easiest way, if they have record.
 
You must log in or register to reply here.
Back
Top