4l80e shift points

[wholzgrefe89]

hey i have a 1993 k2500 pickup with 6.2l diesel and a 4l80e trans and it seems like the engine reves up pretty high before it shifts idk if this is normal or not. From first to second it hits pretty hard when it shifts but from second to third and third to OD it shifts fine it just revs up high the fluid looks clean idk about the filter i just got the truck about a week ago.


thanks

[bigblock72]

Originally Posted by wholzgrefe89

hey i have a 1993 k2500 pickup with 6.2l diesel and a 4l80e trans and it seems like the engine reves up pretty high before it shifts idk if this is normal or not. From first to second it hits pretty hard when it shifts but from second to third and third to OD it shifts fine it just revs up high the fluid looks clean idk about the filter i just got the truck about a week ago.


thanks

Shift points are determined by the programming in the transmission control module, so if it shifts it's normal.

The hard shift into second is a little abnormal and may be a sign of a broken accumulator spring but isn't anything to worry about until more serious symptoms show up.

[wholzgrefe89]

Alrighty I'm gonna try the Lucas oil transmission stuff when I change my filter and see if it helps
And I noticed this morning when I drove to work it didn't rev up high before it shifted

[GenBiltstein]

The shift points are determined by a few factors. One being the Throttle position sensor on your truck.
Before you do anything else I would check into the TPS (as it is called fo9r short) for a correct adjustment.
A misadjusted TPS can cause erratic shifting.

[wholzgrefe89]

well it stopped reving high but now it shifts really fast even if i floor it it short shifts and when im on the highway when i go to pass a car it dosent down shift it seems like it bogs a little and takes along time to build speed whats going on with that?

thanks

[GenBiltstein]

The TPS needs to be adjusted correctly.

Find out what you or someone else did before the transmission went to late first shifting.

[turbonator]

It seems like the TPS to me to, it might be starting to have ''dead spots'' in it and giving bad voltages to TCM.

[GenBiltstein]

To check for dead spots.
Ohms on a multimeter. Find the pin taking live voltage in from the computer. Find the resisted pin that sends information to the computer. Easily done. Pin A and Pin B
Set the multimeter on resistance. Handthrottle it slowly you will see a graduated decrease in resistance. There is one dead spot left in the TPS on purpose. This is to downshift.
Also check for live voltage coming into Pin A
Check for a solid ground signal out of Pin C

Just for good insurance
Take the same multimeter and check every living ground terminal you have. Anything above .02 take apart the ground terminal and clean it.
That multimeter is a labor saver and prevents you from guessing which grounding terminal is unserviceable and prevents you from reaching those hard to get to terminals that might be serviceable anyway.