BBC632Camaro

iTrader: (82)

LS1/4L80e swap into 66 impala. Just finished everything up and I'm having problems with my swap showing DTC codes P0740(tcc solenoid) and P0785(3-2 shift solenoid). The transmission was out of a early 90's motorhome with the old style plug so I upgraded the internal harness with a new harness(plug-n-play) and installed an transgo hd-2 kit with a new black pressure solenoid as per instructions of a very good transmission sponsor on here. The kit was easy to install and everything seemed to go smoothly as I don't believe there to be anything wrong there but I suppose thats still a possibility.

When you drive it, PARK-REVERSE-NEUTRAL all seem to work like they should. But when you put it into DRIVE or OVERDRIVE it starts out in 1st gear but shifts very rapidly and bogs the motor to 2nd and so-on to 3rd. I think its going into limp mode when its doing that. Also it never downshifts and seems to favor 2nd gear. When you manually shift it it seems to shift ok but sometimes doesn't go into first and stays in 2nd.

Also one thing we noticed is you can clear the code and turn the key on but it won't trip the code until the car is actually started and running. One mechanic said it should usually trip with the key in the ignition spot.

Yesterday I took it to a mechanic and he says there is power down to the transmission plug and THINKS everything seems to be ohming out and checking out ok. I'm stuck scratching my head and about ready to pull my hair out on this thing... Can anybody give me some good knowledge and what to do or check for to remedy my problem? Thanks in advance...

slow67

iTrader: (2)

It sounds like a segment swap wasn't properly done.

BBC632Camaro

iTrader: (82)

Thats what I'm thinkin it is too. Is there anybody here that I can email my tune to to fix this for me and send it back? I have hptuners and would like to have the car for a car cruise tomorrow night. Anybody??

slow67

iTrader: (2)

Those solenoids aren't used in an 80E. Have you tried just disabling the codes?

BBC632Camaro

iTrader: (82)

I was gonna try that cause in my research I remember reading to disable those 2 codes and another one (P1860?) when swapping a 4L80e but didn't know if it was good advice or not. I'll give it a try and report back.

BBC632Camaro

iTrader: (82)

Well Idk if those codes are suppose to be active or not but I think I found the problem. The VSS is reading way too fast. When I drive a true 65mph my pcm says its doing 94. I don't have a spreadsheet or anything like that to know what to switch them too. Does anyone have a spreadsheet for this? Slow67 your help has been greatly appreciated!

slow67

iTrader: (2)

PM me your email address.

And no, those codes shouldn't be active.

jinx44

Hey guys, ran across this thread while trying to fix a problem with a '99 half ton SBC/4L60 truck. Recent trans rebuild, and immediately after install it went into limp mode and threw P0740 and P0785.

I found some info pointed to the ignition switch. Since the thread is current, I figured I would join and pass along the info I found. I am guessing you swapped an ignition switch also into that Impala.

http://chevroletforum.com/forum/gene...olenoid-26085/

I hope this helps.

Oh, and since I am a mustang guy.....I should add in my first post on this board that LS1s suck.

Grendel

iTrader: (27)

Thanks for this... I had the same issue.

HD 4L80E swapped into my 68 GMC C15. Wiring seemed right, went nuts trying to figure it out.

Turned them off in HPTuners.

84 K20 LTZ

I'm having this issue with my swap, 84 K20 4L80 208 t case. Did the repin and added the ISS in trans and OSS pulse generator in T case. Im getting speed feed back prom the ecu through my scanner and it matches the speedo as well as GPS. truck starts in first shifts second to third then stays there doesn't start over in first unless i shut it off. Giving p0740 and p0785 codes. ecu was originally programed for 60 had it segment swapped to 80. i assume the codes weren't disabled.

truckdoug

iTrader: (25)

the p0785 is a 60e specific code. the computer is looking for the 3-2 shift solenoid (which the 80e doesnt have) redo the segment swap. save it as a new file and do a write complete. if it's still doing it, try turning off high-speed writing. ive had some odd issues with this as of late.

5.7stroker

iTrader: (36)

Doug, a few questions on this.

1. Do you have to disable those 2 codes before doing the segment swap? If you just uncheck the SES enable for those codes on a tune file that has been 4L80E segment swapped, aren't you good if you simply uncheck them and select "No error reported".

2. Does one do this only for the p0785?

3. Is there a list of codes that are 4L60E specific that I should uncheck for SES and select "No error reported" after doing a 4L80E swap into a car that had the 4L60E?

4. I notice that on the 4L60E tune it has all the same engine DTC's checked as the tune that's been 4L80E segment swapped. The difference in trans diag can be seen in the image below, with the 4L80E segment swap tune on the top which contains the stock settings, and the 4L60E tune on the bottom. I want to use the top values I'm assuming?

truckdoug

iTrader: (25)

if the OS segment swap is completed correctly (both the trans control and trans diagnostic segments) you will not get those codes, nor will you need to disable or alter them.

jimd48CHEV

[QUOTE=truckdoug;20449681]the p0785 is a 60e specific code. the computer is looking for the 3-2 shift solenoid (which the 80e doesnt have) redo the segment swap. save it as a new file and do a write complete. if it's still doing it, try turning off high-speed writing. ive had some odd issues with this as of late.[/QUCan you pm me I am having some problems with a 4l60e to 4l80e swap? Thanks

jimd48CHEV

I am having the same problems with po740 and po785. Person that did segment swap says its done correctly. You can pm me if you like

Tranzman

Ditto @slow67 comment. 4L80E doesn't have a 3-2 solenoid. Check to make sure your tune is for 4L80E. There is more to a 4L80E segment swap then just checking the drop down box for the 4L80E...
See pages 112,113 of the attached VCM editor PDF.

Tranzman

upload the tune file here! I can look at it...

Tranzman

there is a HPtuners link shared in another thread. it's funny two different threads with the same issue It was shared by @jetech I honestly thought someone double posted LOL also didn't realize it is a 10 year old thread...

https://ls1tech.com/forums/automatic...-problems.html
here is a direct link to what he had to do to fix it.
https://forum.hptuners.com/showthrea...MC-Sierra-1500

Let us know where this goes...

Tranzman

@jimd48CHEV any news on your issue???

jimd48CHEV

have been delayed because of sickness in the family,have the 4 prong brake light switch to be installed 1st to see if it cures any problems.