: any tranny experts out there?



parts68
04-22-06, 11:03 PM
95 is acting up every once in a while.
Trans will go into default mode and stay
in 2nd gear because it thinks the shift solenoids are bad.
Ive replaced the solenoids,valve body gasket and done a complete
clean and replacement of filters and fluid.
Ive observed the amperage of both desired and actual for the pressure control solenoid and it appears to get alittle off every once in a while.
Ive never caught it in the act but as soon as I get out of car and someone else (normally a female driver)drives it will act up.
I think I have a work around for this as it does set a code,but need some more info before trying.

JC316
04-23-06, 02:36 AM
Have you checked the wiring at the transmission, where the harness connects? It's fairly common to get a corroded or loose connection there.

parts68
04-23-06, 08:01 AM
yes I have thanks
I think its more of an issue with PCS itself or maybe the wiring inside the trans
trying to avoid R&R of trans to find something minor.
Actual amps on PCS do follow the desired amps quite closely but apparently
it hiccups once in a while,sets code and defaults to 2nd gear.
By the time I get in it,the code has cleared(stored in history only) and car is normal.I drove the car for 200 miles for 2 wks and zero probs,even beat it hoping I would catch in the act.

acklac7
04-25-06, 12:20 AM
Maybe there is something clogging the valve body??? I know that if the fluid fails to pressurize the solenoids the solenoid trouble codes are thrown...Maybe there is something floating around inside the valve body....All of a sudden that "something" blocks a critcal passage, and fluid cannot reach the solenoids..Then once that "something" gets sucked through the passage everything is fine...Untill it eventually blocks the passage again....That is what I believe happend to "boom"....read the entire thread...see if these symptoms ring a bell....http://caddyinfo.ipbhost.com/index.php?showtopic=7590&st=0

I have heard that numerous dealerships are now recommending the valve body be updated/replaced when the solenoids are replaced...Maybe post-solenoid issues are a common problem?....I will say that when I had my Trans. rebuilt the shop manager said they where installing a valve body update that Cadillac had put out...Never did verify exactly what "update" they were talking about.

parts68
04-25-06, 09:24 PM
every thing is squeaky clean
new fluid(old fluid wasnt that bad)
I removed the valve body and cleaned it with brakekleen
and installed a new GM valve body gasket.
Ive heard that the spool wears out on the valve bodies
made of aluminum.
A friend with tranny shop said hes even bought a reamer for oversized
spools. This isnt limited to 4t80e tho

chevelle
04-25-06, 09:36 PM
I would be looking for a loss of 12 volts to the transmission. The solenoids are fed power and then the PCM pulls them to ground to activate. If the trans looses power feed then the solenoids cannot activate no matter what the PCM does and the trans hydraulically defaults to 2nd gear when the shift solenoids drop out. Possibly a temporary indicator light on the 12 volt feed or a VOM tap to the 12volt feed at the trans connector so you can check when it does happen.

parts68
04-26-06, 05:47 PM
OK Ill try that but Im really suspecting that its getting power and the fluid pressure is spewing out of an internal seal.
I think the fault code is set via pressure not voltage to the solenoid.
If that were the case a broken solenoid would still get voltage but trans would have no way of knowing it failed.
Im going to dig out my Snapon trans diagnostic book and see what it says.

parts68
04-28-06, 05:57 AM
Ive already had one bad PCM(full line pressure) and maybe the replacement one is bad too.(Different problems)

1993 eldorado green1
04-29-06, 01:05 AM
Ive already had one bad PCM(full line pressure) and maybe the replacement one is bad too.(Different problems)



i too was having a intermitten problem with code p076 and it was a bad pcm. it would be fine when it was cold then as soon as she warmed up it would set the code...

parts68
04-29-06, 07:51 AM
yea that PCM that caused the code P076 was flaky
one day it finally broke for good and stayed with full
line pressure.
I switched it with another and it worked fine.
Now it seems that the extreme line pressure must have blown
out a seal on the clutchpacks as its starting to slip(never did that before)
and acts funky.
I have a 99 trans Im ready to install but no one can tell me why Hollender says
99 wont work for replacement of a 95.

1993 eldorado green1
04-29-06, 10:48 AM
yea that PCM that caused the code P076 was flaky
one day it finally broke for good and stayed with full
line pressure.
I switched it with another and it worked fine.
Now it seems that the extreme line pressure must have blown
out a seal on the clutchpacks as its starting to slip(never did that before)
and acts funky.
I have a 99 trans Im ready to install but no one can tell me why Hollender says
99 wont work for replacement of a 95.

i will see if i can send u the mitchell wiring diagram of both the 95 and the 99, that will give you more of an idea if its gonna work or not.
i know the motors interchange so the trans would have to bolt up. the electrical is the only thing i can think of that would be different..

parts68
04-29-06, 01:48 PM
see my post on this.
I think I have the differences figured out but want to make sure
maybe a second opinion.
I have the wiring diagrams and pinouts and it looks the same on both.

parts68
05-19-06, 08:51 PM
99 tranny works great
not exactly a boltin but it wasnt
that bad.