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Short story
I had a 1996 Chevy truck 4L80E diesel come in with occasional 2nd gear
only. It only does this when it gets HOT (TFT above 150F). Scan codes and
got a 86. I took a movie and captured the code 86 and seen that all input,
output and engine sensors were reading right. Only thing I seen was the
TCC slip was over 200rpms while PCM was commanding it to be PWMed on full.
No glitches, just plain ole something slipping. So I clear the 86, put the
transmission in D, and take it for another road test to see if I can
pinpoint the actual slippage. Sure enough on the road test I found that
the input and output sensors read exactly the same, but the engine and
input were off about 200 rpms while TCC is commanded on fully, and this
time it tripped code 39. So I KNOW it is the TCC slipping. Put the
TransX2000 and manually shifted and applied TCC, still slipping. So I put
up all the electronic stuff and got out the old transmission gauge.
Pressures were all good, even when hot. Next step pull up all bulletins.
ATSG had a bulletin for TCC shudder, to turn the TCC regulator valve down
.030. So I pulled the VB. and modified the valve and put in a new PWM
solenoid. Same problem. So I figure it's the converter, or pump. Pulled
it out replaced the pump and converter, same problem. Well, pack to the
drawing board. I pulled the VB. and replaced it..................BINGO
it's FIXED. I guess the bore is wore out in the VB. for the regulator
valve, but I can't detect it. Are we going to have to start building VB's
like engines? Bore-em out and put oversized valve in them? I realize the
PWM regulated valves are really busy, so let's have a fix!
Dan Tucker
Transman@Prodigy.net
Dan whats the purpose of turning down the TCC REG.Valve if the bore is
worn?? or have I missed something??
Bob Ryan--
1st R.A.T.E. LTD.
London
U.K.
www.firstrate.demon.co.uk
bob@firstrate.demon.co.uk
Bob,
I am sorry if I mislead you about turning the valve. Actually all you do
is slightly shorten a land (.030). It allows a little more oil volume flow
as I see it, though it didn't work in my case. It's an ATSG bulletin.
Dan Tucker
Transman@Prodigy.net
Gentleman, I don't want to instill preproduct hope...but you can be assured these valve body, premature wear out's are being addressed. On all those units of concern. BWSonnax
I've seen this quite often on 4l60e and 4l80e its ok to block the valve
with no side effect
Transmaster@webtv.net
Transmaster,
Exactly how are you blocking the valve on the 4L80E? Is it too aggressive
being blocked?
Dan Tucker
Transman@Prodigy.net
put the spring on the opposite side of the valve pinning it all the way
in you may need to trim some off the spring this makes it like a on off
type feel not too agressive
Transmaster@webtv.net
the valve is in the valve body its called the tcc regulator valve when
you blocked the pryou sent it into max pressure
Transmaster@webtv.net
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Truck sent by local dealer, no 3rd , no codes stored, PRNDL shows ok but not in 3rd, in O/D upshifts but skips 3rd, pull to third from o/d freewheels. Changed "pms" & still same problem, any idea's ??? unit has 2nd Certa unit installed along with new "computer". At quick glance wiring looks ok.
Ken B.
Subject: 4L80E No 3rd Gear Put on your scanner, and see if your output shows rpms...I had a srta that had the sensors reversed (connectors)..it ran for 2 1/2 years...I know that the book says that they can not be reversed, NOT SO. Otherwise ran well and if you were not transmission literate, you could well miss it.. No quarantee, but wanted to advise. Jimmy Taylor and Ron Widing are really sharp on this stuff...Consult.
Jim, III stardust@frontiernet.net
With both transmission and computer been replaced, the only thing left is the harness. Look at the harness carfully. It's possible a wire has rubbed apart, most likely near the engine/trans/firewall area.
The real question you should ask and find out, is Was this the original problem or did it develope after the first SRTA unit was installed. You might just find a mashed wire loom somewhere. --
Jimmy Taylor (odie@alaska.net)
Taylor's Transmission Service, Inc
Anchorage, Alaska
Look to see what the computer commands when you shift to 3rd. If it says it's commanding 3rd, then I would suspect the solenoid wires were crossed. But not in the trans, in the harness. Did someone put on a new harness and get some wires mixed up? Sure sounds like it to me. --
Jimmy Taylor (odie@alaska.net)
Taylor's Transmission Service, Inc.
Anchorage, Alaska
I had a similar problem. Found the solution to be shift solenoid 2 to be stuck open, thid will cause the trens to neutral in 3rd. I sugest dropping the pan and mechanically checking the shift solenoids.
Ken,
If you are saying this is the 3rd trans with the same problem, you have to have something with the vehicle causing this. Otherwise the following may be of help:
TH 4L80-E TROUBLE GUIDE #16 Page 1 of 2 NO 3rd GEAR
1) No signal to shift solenoid "B" from PCM.
2) Loose connector to shift solenoid "B".
3) Missing "O" ring seal on shift solenoid "B".
4) Shift solenoid "B" (2-3 solenoid) stuck "OFF".
5) 2-3 shift valve in valve body stuck.
6) Valve body misassembled during overhaul - see Page 2
7) Quad driver module failure.
8) May store fault codes 81, 85, 87.
9) Center support bolt not tightened.
10) Direct clutches burned or worn.
11) Center support cracked (Not always visible).
12) Sealing ring on center support defective.
TH 4L80-E TROUBLE GUIDE #16 Page 2 of 2 NO 3rd GEAR
From ATSG bulletin 95-01
May be caused by misassembly of 3rd/Reverse checkball bushing and bore plug in the valve body. The roll pin retainer should be completely behind the bore plug, not through it. The roll pin should be visible when looking at the end of the bore if assembled correctly.
Hope this is of help,
Ron Widing
Griffith, IN
TransDoc@juno.com
Jim:
Thanks for the reply, I found a bit more info about past history today. The
first trans lost 3rd & O/D , dealer then installs CERTA unit along with new
controller, that trans blew the direct drum in 2 pieces, now this CERTA has
no third. I drove it this morning myself (my builder has put a new mps
sensor & no change), shift lever matches on scan tool except drive ...
shows 2nd & O/D shows nuetral ..... next step is to check signal at trans
on three mps wires at case connector & then at the controller (have not had
time yet or a bay free).
My logic is that the trans must be ok if 4th gear works (direct cltuch is
applied in 3rd & 4th... right ??). Controller is sending signal for 3rd
according to scan tool, but what I can't figure out is why does it
freewheel in third if the shifter says it's in 2nd. What is your opinion on
this (sorry for the long post).
Ken Buehler
Buehler Automotive & Transmission Inc.
Alma Ont
519-846-9221
IATN Sponsor Member
kbuehler@freespace.net
The fix for the 94 Chev 2500 4x4 was a new PMS sensor & trans harness & all was well. Thanks for all the replys, this is a very supportive network.
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This is one where the customer didn't have the money for a rebuilt so I installed a used transmission in this 84 Eldo. Northstar, Pan was spotless and the fluid was still like new. Trans will shift good the first time you pull out but after you stop it shifts real hard and sets an 86 code which is a bad Transaxle presure control solenoid, Pulled the trans out and did an ohms test on TPC and it read 4.1, Checked the one from the old trans and got the same 4.1. Is there any other way of checking these that anyone knows of. This is not a gravy R&R so I would like to find the problem for sure before we put it back together again. Thanks in advance for any info you can give me this
Rick
ALL-PRO Transmission
Rick,
I am sure you meant a 1994 Cadilac with a 4T80E. The DTC 86 is a RATIO
error. It could it be the sprockets or diff ratio are different? I am not
really sure about this but it is something to consider. You might could
flash the computer to the type of car the used transaxle came out of. Or
maybe get the PCM out of the used car if compatible. I don't work on to
many 4T80E Cadilacs, but if you can get the data stream to read TCC slip in
3rd gear with the TCC applied, the ratio should be 1:1, and TCC slip around
0. Please post your findings.
Dan Tucker
Pine Bluff, Arkansas
Transman@Prodigy.net
Any time a code appears for the EPC solenoid you should verify the condition of the starting and charging system. GM monitors the current draw of these devices. A code will be set if the current is too high or too low. While this is great for determining when the solenoid coils either short or open, it can cause false codes when there is no solenoid problem at all. The reason is this, Current draw is determined by dividing the vehicle voltage by the solenoid resistance. If the vehicle voltage is too high, or as often occurs too low, the current draw will go out of the limits allowed by the computer, and there is your code. In as far as checking the solenoid.. There are no codes that relate to a mechanically malfunctioning epc solenoid. The computer has no way of telling what pressures the solenoid is putting out. All the computer can do is monitor the solenoid current draw. A resistance test will verify the integrity of the coil. For a real life test, use a transmission tester and pressure gage. Cotrol the duty cycle of the solenoid and watch the pressure rise and fall. As far as aftermarket solenoid testers.. Forget it there is not a one that can duplicate transmission conditions.
Scott Kirkendall
http://www.rostra.com/
Turned out that the gear ratio was differend than the original trans ratio. Was able to change the differenal in the car back to the original gears, There was a big difference in the gear sizes.
Rick
ALL-PRO Transmission, Cleveland Ohio
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1995 olds Aurora trans will hunt for gear two or three times before shifts 1-2
and 2-3.
Has been in the local dealership three or four different times for this
problem. Sometimes when you turn on the car the trans works fine. The problem
is very intermitant. Very seldom does it work right. The TECH 2 has been
installed to try to force the trans to work right. We had no luck with t2. The
codes on this vehicle are 76 force motor problem and 84 too few 24x pulses.
Have been through alldata+snap-on shop key followed diag. flow charts. Shows
to have proper ohms that are required,
when acting up. When trans is working properly ohms fall to lower resistance.
Sounds like a hydraulicly failed solenoid. How many miles on unit. Has force motor ever been replaced. These babies get a workout.
Chuck from Charlie Tranny in Belleville, MI
Whomever,
There is an ATSG bulletin regarding Turbine shaft speed sensors going bad. A revised sensor has been brought out it has part no. 8685 532. When it is defective it usually gives a code P056, but this sounds to me like a possibility in this case. The bulletin recommends replacing this sensor with the new number during all overhauls since it is mounted internally and cannot be changed "in car".
Ron Widing
Trans Diagnostic Software
Transdoc@juno.com
Griffith, IN
Sounds like a voltage problem, can you run a 12 v from battery to connector and see if it solves your problem.
Len
NJ
lmaru@aol.com
Hey guys the 4t80e that hunted for shifts is fixed.We replaced the control module and taught it how to shift again and it works great. Thanks for all the support in helping me figure out this problem.
later, Bobby @ TROYS TRANS
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Greg Hibler
Greg: I've been hearing rumors that GM has embraced the Ford computer strategy of the computer remembering the codes and an almost inability to clear them. What concerns me is that you changed the computer and had the same problem. Do you have any thoughts on this. This computer business is killing us.
Jim, III stardust@frontiernet.net
I think that we are going to have Dan Tucker answer this question. I also have a question... Dan if the computer is flashed, are the codes deleted?
Thanks, Jim, III stardust@frontiernet.net
HI Jim,III
Dealership said comp. had to be programed to car.I don`t know if they take any programing from old comp.or how they did it but i think clearing codes should have been part of prosses But we had no problem clearing them
Greg Hibler
Jim III,
That is a good question. The codes DO say during flashing an EXISTING VCM. As for how the SPS Expertech flashing works on a new VCM, the VIN number is entered manually into the Expertech program on the PC, then it retrieves the correct software to operate the vehicle off of the GM CD. Once the software is found on the CD the PC then sends it to the NEW VCM. So the chances of the new VCM get HIV from the old VCM is impossible. At least with the system I use. The dealer's flashing system works a little different, but it uses the same software. I guess you could say, we use a sterile needle. There is also no way, I can see, that the codes could get transferred to the new VCM.
Dan Tucker Pine Bluff, Arkansas Transman@Prodigy.net TRNi and TRN2 Member
Jim III, every reflash I've done in the dealer has always cleared any codes. But, then again, disconnecting the battery, usually clears codes for me and GM says that's not supposed to happen. LarryU
Dirk Stardust wrote:
Well there was no response to this post but there is a fix. After hours & days of checking wiring & many calls to ATSG--ATRA & olds dealer the fix was to replace comp. After replacement took to dealer for programing car came back with same problem .Put snap-on back on bunches of codes cleared codes drove great no codes returned ben gone a week IT`S FIXED code 84 is crank sensor code
Greg Hibler
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