Diesel Place banner

1 - 14 of 14 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
My 93 6.5 2500 Silverado kicks me out of overdrive when I exceed 80 kmph. I have been reading into this very common issue extensively - And so far have done these to try and fix:

New Throttle Position Sensor (Correctly adjusted)
Verified input and output speed sensors
Verified reluctor on transfer case
New torque converter
REBUILT transmission.

after all this - all that is left is the Torque Converter Clutch solenoid to try and swap out. But I'm not convinced - i have noticed this:

Once i get up to speed - 75ish - if I depress the brake pedal ever so SLIGHTLY, (as if to disable cruise control) so enough for that switch - but not enough for the brake light switch - and two-foot drive - I can exceed 80, without getting kicked out of overdrive. As long as I keep that brake slightly depressed I can prevent it throwing DTC 68.

Any insight would be greatly appreciated!

On a side note - speedometer, odometer, and trip meter are not functioning. (New dash did not fix those)
 

·
Registered
Joined
·
183 Posts
Check out in order:
1 VSS
2 TCM
3 Wiring
 

·
Registered
Joined
·
82 Posts
Did you ever figure it out? What was the fix?
 

·
Registered
Joined
·
20 Posts
My 93 6.5 drops out of overdrive and lockup after driving aprox 20 miles. "completely warmed up" Shifts normally until then. I have replaced the 4L80 transmission / the TCM / the ignition switch and I'm at my whits end. Could it be the TPS doing this? the Speed sensor seems correct by the output of the tachometer. Help?
 

·
Registered
Joined
·
3,931 Posts
Could be the ESS, the tach gets it's signal from the alternator.
Have you checked for codes?
 

·
Registered
Joined
·
3,931 Posts
22 is TPS signal.
Make sure the GREY wire on the TPS has 5v. with key on.
68 is slippage.
Could be actual slipping clutches or TC, or bad ESS signal.
Could also be bad ISS/VSS signals but those usually set a code.
Does the speedo work?
 

·
Registered
Joined
·
20 Posts
The speedo works normal, the tach seems to work normal but gets a little jumpy when the tranny goes into limp mode. The engine speed sensor in the 93 comes off the cam shaft worm drive "where the distributor would go". I'm wondering if the plug or the wires are shorted back there or if the speed sensor is bad.
 

·
Registered
Joined
·
3,931 Posts
The tach signal comes from the alternator.
The jumpyness could be actual engine RPM changes or maybe an electrical problem.
Your 4L80 has 2 speed sensors, they are the same part on a 2wd.
The TCM compares the ESS, ISS, and VSS signals to determine slippage.
Wiring could very well be a problem on a 93 rig.
Have you read the codes with the engine running?
You should NOT get the 12-12-12 with engine idling.
Code 12 is the "no engine rpm" you get when the engine is not running.
 

·
Registered
Joined
·
20 Posts
I just took the truck back to the shop that replaced the transmission. They are in contact with the tranny supplier to determine if the problem is in the transmission or one of the sensors. I am forwarding your input to them - I think this problem may be out of their league - hoping not. what ever is the problem it was getting progressively worse with each drive. I so appreciate your help - I'm stymied.
 

·
Registered
Joined
·
20 Posts
Street Smart transmissions authorized replacement of the new re-man transmission with the the understanding that I would replace the throttle position sensor and the tranny cooler with new parts. I will do a follow up to this thread when the work is complete.
 

·
Administrator
Joined
·
15,674 Posts
Street Smart transmissions authorized replacement of the new re-man transmission with the the understanding that I would replace the throttle position sensor and the tranny cooler with new parts. I will do a follow up to this thread when the work is complete.
Make sure you use AC/Delco parts only and take pictures of old/new parts and keep receipts of the parts you purchase.
This way, if you have another bad trans they cannot throw it back on you.
You will have proof of required parts and receipts.

:thumb:
 

·
Registered
Joined
·
20 Posts
So, Street Smart Transmissions agree'd to replace the first reman transmission they sent. The shop installed it and replaced the Throttle Positioning sensor along with a new Transmission cooler. It still drops out of 4th gear and lockup after the truck is driven about 20 miles or so and it's fully warmed up.
So, I've now replace the Transmission control computer, the ignition switch, the transmission, the TPS and the cooler. The only thing in the chain that has "Not" been replaced is the ESS - the one that runs off of the oil pump gear in the back of the motor. Do you think that could cause the problems of the dropping out of gear? My shop is perplexed and I'm about to look for a outlet for dynamite.
How do you check the ESS to find out if it's working? The Tach. seems to indicate normally.
Help!
 
1 - 14 of 14 Posts
Top