4L80E 4rth Gear problem

[almusafir]

I have to face one problem from 7/8 days...
in Transmisasion 4L80E We overhaul it...
now the problem in 4rth Grear

I have this Transmission in GMC Truck 454 Engin Model 1990.

Shifting is OK.. But
When It became in 4rth Gear and I press the full accelator the care take the kick down and become in 3rd... then its runing in 3rd.. never became 4rth until you stop the car. and switch off the Car..

Can you please help me for this..

[joecar]

Almusafir,

Welcome to the forum... :cheers:

Please post your .tun file (do Go Advanced->Manage Attachments, and then Browse, Upload).

When this condition is present (no 3-4 shift after 4-3 WOT), do you get these shifts:
- 3-2 kickdown (WOT)
- 3-2 part throttle (PT)
- 2-1 PT
- 1-2 PT
- 2-3 PT

If you get thes other shifts, then possibly the 3-4 shift valve may be sticking.

Attached page is from the 4L80E Technician's Guide.

When this condition is present, monitor the GM.GEAR and use the BiDirectional controls to command 1st, 2nd, 3rd, 4th;
does GM.GEAR show each of these being commanded...?

[joecar]

Checks Cause

Fourth Clutch Components
Seals (527) (531) Nicked or cut
Cup Plug (530) Missing
Bolt (26) Loose, broken, or missing
Piston (528) Jammed
Spring Assembly (532) Jammed
Retainer Ring (523) Not seated
Friction Plates (525) Worn or burned
Reaction Plates (526) Worn splices
Housing (529) Damaged or crackedOverrun Clutch Components
Housing (504) Broken
Reaction Plates (508) Worn splines
Sun Gear (650) Worn
1-2 Solenoid (313) Stuck Off, Pinched wire, O-ring failure, No voltage to the solenoid
PCM No signal to the solenoid, Failed
3-4 Shift Valve (308) StuckCheck the PCM for current DTCs.

[joecar]

I assume you are using a Gen III/IV PCM and have fitted the necessary hardware to your 454 for the PCM to operate the engine and transmission...

Which part of my assumption is incorrect...?

[almusafir]

Almusafir,

Welcome to the forum... :cheers:

Please post your .tun file (do Go Advanced->Manage Attachments, and then Browse, Upload).

When this condition is present (no 3-4 shift after 4-3 WOT), do you get these shifts:
- 3-2 kickdown (WOT)
- 3-2 part throttle (PT)
- 2-1 PT
- 1-2 PT
- 2-3 PT

If you get thes other shifts, then possibly the 3-4 shift valve may be sticking.

Attached page is from the 4L80E Technician's Guide.

When this condition is present, monitor the GM.GEAR and use the BiDirectional controls to command 1st, 2nd, 3rd, 4th;
does GM.GEAR show each of these being commanded...?

Thanks Sir...

But still same problem..

it appear code no 68

[joecar]

I don't have an early GM manual with me right now, what does DTC 68 mean...?

Oh, you're using the OBD-I ECM.

[Biggsy]

Off the top of my head I believe code68 is a trans slip fault

Cheers,

[almusafir]

I don't have an early GM manual with me right now, what does DTC 68 mean...?

Oh, you're using the OBD-I ECM.

Yes...

I 'm using OBD-I ECM..

I think Code
68 means

Cruise control - system
circuit problems.
OR
Air Conditioner (A/C)
clutch relay - short circuit.
OR
(Transmission) Overdrive
ratio error - engine RPM
greater than input speed.

[almusafir]

Off the top of my head I believe code68 is a trans slip fault

Cheers,

No Sir code68 appearing...
Transmission Shifting is fine and OK.. But when you became 4rth Gear and you press full accelator it takes Kick down and coming in 3rd... Then it never change of 4rth.. until you stop and switch off the car..
When you shitch off the car and start is again its ok in normal

[joecar]

"Overdrive ratio error" means the fourth clutch is not applying;

when the fourth clutch is applied, it holds the overdrive sun gear stationary which causes the overdrive carrier assembly to "overdrive" the forward clutch housing (where the input speed is measured).

Edit: if the fourth clutch is slipping or not applying, then the input speed measured at the forward clutch housing will be wrong, and the PCM raises the code.

See the blue, red, gold components in the next post...

[joecar]

http://img85.imageshack.us/img85/9011/4l80e4thjc0.png

[joecar]

If the fourth clutch is not applying, then the overdrive sun gear (blue) is not held stationary, which means the overdrive carrier (red) does not "overdrive" the forward clutch housing (gold)... so you would get the same effect as being in 3rd gear.

This means that the fourth clutch piston could be getting jammed (since you said it went into 4th once, and after kickdown it would never go back into 4th unless engine was shutoff first)...

The ECM is commanding 4th gear, otherwise it would not check the input speed and set code 68.

[almusafir]

I think May Be I got the point...
Let me check

[joecar]

Could also be the 3-4 shift valve sticking (see next post), this is easier to check than the 4th clutch jamming.

[joecar]

http://img360.imageshack.us/img360/5036/4l80e4thvalveses1.png

[joecar]

Also, read the note about orifice #7 and the orifice plug in the 4th clutch housing.

[almusafir]

Thankx for nice coaprative... I'm checking these now

[almusafir]

Still at last the Code is not removed...

8 time Repaired the Transmission...

4 Egineers came but all are faliaure.

At last I changed the transmission .. as the transmission 4L80E
the model of 98 ...
Its working very fine.
Now just showing the code of 58 of the temprature sensor.
b/coz in this model there is not temprature sensor inside...

Now what is opinion?

[joecar]

I think there may have been a problem with the transmission case.

4 Engineers were not able to find the cause of the problem...???

The new one works fine, that's great... :cheers:

If there's no temperature sensor, find the 2 wires for this in the harness,
and connect a resistor of the right ohms to simulate 170°F-180°F or 77°C-82°C...
otherwise the ECM may set line pressure to maximum.