I rebuilt a 4l80e (my first rebuild) and swapped it into my 07 Chevy tbss awd. Stock rebuild, replaced all the steels,clutches, bushings, sprag and one way bearings. I did instal a transgo HD kit that was recomended by a local trans shop. I followed a few manuals during the project, everything measured within spec. Got a new converter. Im using a pcmofnc adapter harness, and a ECM and TCM from them setup to get a 4l80e running in a tbss. After getting it together I struggled for way too long to figure out why it was getting a inconsistent half speed signal, long story short I learned that post 96 4wd 4l80es dont have a vss reluctor ring in them. I had to make a diff yoke flange vss, speedo works great now. Driving the truck, it hangs into first too long and jumps to 3rd then 4th. Shifting from 1 - 2 - 3 manually, it stays in 1st, I can feel something slightly happen but not a gear change. I also feel a slight "shudder" on decel and light accel like the converter may be locking up at the wrong time? On the datalog, it says that the current gear is 2, but it never left 1st.

I dont want to throw parts at it, I did too much of that on too many other gremlins. Researching it sounds like I have burnt clutches, bad solenoids/wiring, or low fluid. I can confirm the fluid is not low, may be on the high side which can be a problem I know. Im only posting in hopes that the datalog will make it obvious that its clutches or a solenoid. Any thoughts or info would be greatly appreciated!

 

My first guess would be INT sprag in backwards but been a while I think that would cause a bind up in 3rd. So broken or missing centersupport bolt with hole in middle, broken second apply piston or damaged seal . Missiing 2nd acumulator in low/rev servo or seals, I would check the low/rev servo 2nd accum first .

 

Thanks for the reply Frank! I will check whatever I can before having to drop the trans. I installed the centersupport bolt, I believe the trans go kit included an “upgraded” bolt. I’m considering buying new solenoids and internal harness while I’m in there. I took care installing all the of the apply pistons, lubed them, and used stencil film to slide the lips in. Doesn’t mean I didn’t screw it up though.

 

If you unplug the large connector on the transmission, the unit will default to 2nd and reverse only. If you have forward movement with harness unplugged, then you know 2nd is physically there, and you know you have an electrical or command issue.
Is your adapter harness pinned correctly? Confirm ECU and TCU are tuned and segment swapped correctly?
I would also be highly suspect of your external yoke speed sensor. Is the gap correct? Does the mount vibrate? Even if you read the mph ok with your eyes, how does the data look on in a data log? Smooth/choppy? Bad sensor? Try swapping sensors too!

 

The harness is pinned correctly, everything had to stay stock when using the pmcofnc adapter. I know enough to be dangerous on the tune. I purchased an ecm and tcm already wrote for using a 4l80e in the tbss. It seems to be a challenge on this truck/e67/t42 combo.

Everything for the vss seems to be working great. Never any hic ups, and it looks normal on the data logs. I used a reluctor ring from a 4l80e, had a plate machined for the center and then split it in half. The bolt pattern was already drilled before I split it, so all the gaps are consistent.

I will try unplugging the connector this evening to see if it still moves in 2nd. That’s a nice trick to know.


Tbss vss

Tbss vss

Tbss vss

Tbss vss

 

Assuming the external reluctor is because a 4x4 planet was used and reluctor not intstalled internally ? Should not cause issue.
However if second is not functional then even with harness unpluged you will move in 1st just still no second.
I would actually suggest you pull VB and air check second through bolt. Couple possibilities here. You left the 2nd snap ring out , or the case luged snapped off on first apply. It the latter you will find little aluminun chunks in pan . I say this because you mention that MANUAL shift 1-2 you feel something a little. If you have a massive leak in the 2nd clutch circuit cause by one of the above. You would likley get a partcial apply of the INT band which would feel like you decribe like something sorta, This likley proves the vale train is working along with the solenoid . So As I said I would move directly to air checking the INT clutch via the center bolt in case and of course look for little alumun chunks in pan. Another possible I have seen is the sec piston it self broke on first apply (not common) but been doing this long enough I have seen about everything.

 

That’s an easy check. As much as I don’t want it to be that, I would be so relieved to know exactly what the problem is. I will inspect the VB while it’s out. I hope I don’t find the aluminum chunk route! Lol.

Thank you for the reply!

 

I left the pressure plate snap ring out of a TH400 once. No second gear on it either. It bent the return spring retainer & cut the lip seals. Same set up as a 4L80E. Ever since then I test the apply of the intermediate clutch before I go any further.
If you have to take it back out it would be a good time to put the reluctor wheel where it belongs. I do have to say that set up you have looks very nice & rigid. Would work very well until it gets soaked with mud...

 

I will get all the parts I may need on hand to get to the intermediate clutch. When applying air to the center bolt, am I just listening for the piston to hold air? If there is a problem, I assume I will hear an air leak? That’s a great point! When I have it apart I will press on a reluctor wheel. I’d much rather have it stock.

thanks for the reply!

 

I use 40psi air to air test with.
The intermediate clutch is fed directly through the bolt and you shouldn't have much of an air leak
When applying air to the center bolt, you should hear a thud. The intermediate clutch should only have .050-.060 clearance. If you do hear air escaping it could be the lip seals are blown out.

 

Sorry to keep bringing this back up with dumb questions…

For the reluctor ring, will it press on the 4wd carrier just like it would on a 2wd? I’ve not seen anywhere labeling them different.

Thanks for the help!

 

Sometimes the small seals are hard to find separately from a paper & rubber kit. The paper & rubber kit will have everything you need. A local transmission shop may have a box of leftover stuff. They may have it cheap.
The planet is the same, you just press the reluctor over the smooth pary. You just have to make sure it is on enough to center itself in the ISS hole in the case. Local transmission shop may have that too. Or at least let you compare to one that has the ring.