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Hey guys,
I know this is a camaro/firebird forum but there seems to be some knowledgeable people here and I was hoping you could help me figure out this convoluted situation. Im having a hard time figuring out what I need to do to upgrade my 4l80e to work with my LS pcm.
I have a 1991 2500 4x4 Suburban. I kept the original 4l80e and installed a 5.3. From a 2004. I re pinned the harness because the 5.3 had a 4l60e behind it. I segment swapped the trans portion of tune from a 2004 6.0 that had a matching OS. Truck runs great, shifts like hell. Second gear is harsh as is kickdown when I accelerate. Im learning the force motor hz aren't compatible. The part I'm having trouble figuring out is what all do I need to purchase to switch it over to get the newer force motor. If anyone can help me I would definitely appreciate it.
Thought #2 is could HPtuners team solve the issue with software or is the hardware inside the pcm not compatible with the 292.5 Hz force motor?
just put a '93+ epc in it. the LS pcm will know not to run the self clean cycle. just look for one with a black body and no screened orifice on the business end
just put a '93+ epc in it. the LS pcm will know not to run the self clean cycle. just look for one with a black body and no screened orifice on the business end
like this one? Found it from an 05 with the internal harness to match. Your the 3rd person today thats confirmed I just need the new solenoid so im assuming the seperator plate and accumulator housing changes wont bother me?
Thank you!
ps very cool 'burb. love the two-tone. we just this summer finished a '91 with a mild cam 5.3/80e/np241. it was a pretty nice ride. got the stock A/C working and everything. sold o a fella in georgia.
ps very cool 'burb. love the two-tone. we just this summer finished a '91 with a mild cam 5.3/80e/np241. it was a pretty nice ride. got the stock A/C working and everything. sold o a fella in georgia.
I let the 1 year old ac line sit folded over for a year and ruined it but it has a brand new ac compressor on it. That will be the next box to check off my list after this transmission setback.
just put a '93+ epc in it. the LS pcm will know not to run the self clean cycle. just look for one with a black body and no screened orifice on the business end
Thanks for confirming that. Your the 3rd person today that said just change the solenoid and ill be good so I picked up a 2005 solenoid and internal harness to match. I guess the other 2 changes in 1994, spacer plate with deleted hole and accumulator housing won't matter?
Thanks for confirming that. Your the 3rd person today that said just change the solenoid and ill be good so I picked up a 2005 solenoid and internal harness to match. I guess the other 2 changes in 1994, spacer plate with deleted hole and accumulator housing won't matter?
All the 1991 - 1993 4L80Es should get an updated internal transmission harness... the early harnesses were problematic.
I often install the updated style separator plate and accumulator housing, when updating the early cores.
There is a small 3rd piston and spring in the early 4L80E accumulator housing (for the 3rd and 4th accumulators).
It is not necessary... but I would remove the spring and the piston (Blocking it essentially) and install the 1994+ separator plate to go along with your updates.
These parts were eliminated from the transmissions as part of the 1993-1994 updates corresponding with the EPC.
The 1994 (614Hz) EPC does not need the 3rd piston and spring (Torque-Signal fluid compensator/ accumulator) and used an updated accumulator housing for the remainder of production years.
Also, the accumulator valve-train was designed for "soft shifts" that would be more desirable in a heavy truck with high torque and diesel applications.
If the 1-2 shift is too soft (or if the 3rd and 4th accumulators are active), you can remove the spring from the accumulator valve.
The design we (GM) chose for the 4L80E accumulator valve-train, was from the softest shifting design that we used in the THM400.
We did this because the 4L80E was never installed in passenger cars... and because we used the transmission with the 6.2L/ 6.5L diesel prior to the 6.6L Duramax and Allison 1000 combo.
For firmer shifts; a spring can go on the opposite side of the accumulator valve (original spring removed)... just like some of the THM400 transmissions used.
I like this arrangement in performance vehicles.
Last edited by vorteciroc; Dec 12, 2020 at 01:33 AM.
All the 1991 - 1993 4L80Es should get an updated internal transmission harness... the early harnesses were problematic.
I often install the updated style separator plate and accumulator housing, when updating the early cores.
There is a small 3rd piston and spring in the early 4L80E accumulator housing (for the 3rd and 4th accumulators).
It is not necessary... but I would remove the spring and the piston (Blocking it essentially) and install the 1994+ separator plate to go along with your updates.
These parts were eliminated from the transmissions as part of the 1993-1994 updates corresponding with the EPC.
The 1994 (614Hz) EPC does not need the 3rd piston and spring (Torque-Signal fluid compensator/ accumulator) and used an updated accumulator housing for the remainder of production years.
Also, the accumulator valve-train was designed for "soft shifts" that would be more desirable in a heavy truck with high torque and diesel applications.
If the 1-2 shift is too soft (or if the 3rd and 4th accumulators are active), you can remove the spring from the accumulator valve.
The design we (GM) chose for the 4L80E accumulator valve-train, was from the softest shifting design that we used in the THM400.
We did this because the 4L80E was never installed in passenger cars... and because we used the transmission with the 6.2L/ 6.5L diesel prior to the 6.6L Duramax and Allison 1000 combo.
For firmer shifts; a spring can go on the opposite side of the accumulator valve (original spring removed)... just like some of the THM400 transmissions used.
I like this arrangement in performance vehicles.
well, I think I may be chasing the wrong rabbit. Just dropped the pan and it looks like my trans has already been updated with a epc without the hole in the tip. Im assuming its not the 214.5hz epc i initially thought it was.. i haven't checked accumulators. I really want this thing to be old man truck smooth. Im not racing it and have a diesel for towing. Its just a family cruiser. Short of just hoping my 2004 pcm didn't like this black force motor im kinda lost now. I thought for sure I had it figured out. The one on the left is the 2005 im about to put in.
All the 1991 - 1993 4L80Es should get an updated internal transmission harness... the early harnesses were problematic.
I often install the updated style separator plate and accumulator housing, when updating the early cores.
There is a small 3rd piston and spring in the early 4L80E accumulator housing (for the 3rd and 4th accumulators).
It is not necessary... but I would remove the spring and the piston (Blocking it essentially) and install the 1994+ separator plate to go along with your updates.
These parts were eliminated from the transmissions as part of the 1993-1994 updates corresponding with the EPC.
The 1994 (614Hz) EPC does not need the 3rd piston and spring (Torque-Signal fluid compensator/ accumulator) and used an updated accumulator housing for the remainder of production years.
Also, the accumulator valve-train was designed for "soft shifts" that would be more desirable in a heavy truck with high torque and diesel applications.
If the 1-2 shift is too soft (or if the 3rd and 4th accumulators are active), you can remove the spring from the accumulator valve.
The design we (GM) chose for the 4L80E accumulator valve-train, was from the softest shifting design that we used in the THM400.
We did this because the 4L80E was never installed in passenger cars... and because we used the transmission with the 6.2L/ 6.5L diesel prior to the 6.6L Duramax and Allison 1000 combo.
For firmer shifts; a spring can go on the opposite side of the accumulator valve (original spring removed)... just like some of the THM400 transmissions used.
I like this arrangement in performance vehicles.
this makes the second reply that didnt post to this thread. I typed out a much longer reply but it didn't post. Long story short. Transmission already has the black epc in it so I don't think this 2005 epc will help my problem at all. Im at a loss now.
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1991 4l80e behind a 5.3 problems 
