Suburban obd1 headaches

[Kingskid1]

Good day....first off I know this is a Suzuki repair website n in my many years of experience I've never encountered a problem like this n worse no one with a real answer so please be courteous thanks. I have a 91 suburban 7.4L 4L80E a/t 2wd. Since day one of me taking possession of this vehicle ive had these 2 codes that refuse to go away.....DTCs 58 & 59-low & high voltage trans temp signal. DTCs 81 & 82 are intermittent. I rebuilt the trans found burnt friction clutches installed transgo hd-1 reprogramming kit replaced torque converter n all electrical sensors internal and external trans related wiring harnesses. Tested all new sensors. New TPS n properly adjusted, CTS, MAP O2 sensors EGR valve distributor plugs n plug wires insulated n new rewrapped engine wiring harnesses under hood reman cardone ECM (changed 3x now)first 2 ECM replacements showed 2v. Replaced wires from D2 ground pin and D15 trans temp 5v ref. Pin to trans harness connector. Voltage check indicates 7.3v at pin D15 5v ref. N at trans connector. All grounds on vehicle clean tight n checked. Trans works fine for awhile then intermittent 4th gear n lockup operation n hard n early shifts. Pressure gauge shows trans pressures within specs. I have no doubt this is a signal problem n the only component left that hasn't been replaced is the ECM prom which I would change if it was available. Any input would be appreciated n Im in so. Calif. N I don't know n cannot locate a company local that can make or reprogram my prom n ECM so that it works properly. If u know of a company that works n does these things on a obd1 ECM please share the info with me. No cel ever came on but blinks DTCs properly including 12s. Called cardone tech support n no help no suggestions but offered to replace ecms at no charge. Thanks

[fixkick]

we only have a A44DE AISIN MADE BOX HERE, FROM JAPAN, (the old 3sp is GM France, pure hydra, no tcm but does have 1 TCC wire)

does your 4L80E have a separate TCM (no matter where it is,but matters is bad, and where to buy one or get correct one , hard)
most these cars have a TCM (or PCM ) must match the transmission,exactly.

nobody can burn proms. maybe 30 year ago? TCM has PROMS or EPROMS, then ,Uv erased then programmed.) good luck finding old program code for those.... 1991....
GM must be no help. by now.

[fixkick]

so how does it shift? slip, late shifts, early?
is transmission ground strap , present , missing, loose or rusty
.?

[fetcher]

Like FixKick wrote, it may be a Transmission Control Module issue. When you change/alter the valve body springs, it changes the shift points and the TCM
may not be happy with that. When I used to do the all mechanical GM automatics, I liked the extra pressure for the shifts, but for street use, I never liked
how the shift kit held the 2-3 shift for so long so I would always keep the original spring. I would try to get it to work with a stock unit because if you have a computer controlled engine then the ECU may not be happy with your changes. I looked a bit, there is lots on info on modification of that transmission, a number of people say for a street car don't go too crazy on your reprogramming. Anyway, all I wrote is just a guess.

[fixkick]

same here, but
the older the TCM, the more easy it is to fool it, those 91 tcm ARE CAVE man simple and dumb.
not and easy thing to get working now.
good call on spring kits.
leave the box stock is well adviced
is engine overheating? causing the temp sensors to trip.
if not the sensors are failing.

[fixkick]

one more thing. does this box have a TV TRANNY CABLE,>(passing gear cable, or detent cable is other names)
If yes, and missing or dead, or set wrong could wreck shift points, and will cause, the TCM to go nuts.