Question: How to Adjust Passing Gear Kick-down? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
Home Forum Market Place Garage Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > GM Transmissions > 4L80/85E Transmissions. 6L90 Transmission
Register FAQ Forum Rules My Replies My Threads Mark Forums Read Advertise

4L80/85E Transmissions. 6L90 Transmission Discuss the 4L80/85E transmissions found in the 6.2/6.5L equipped vehicles and Duramax equipped vans. 6L90 discussion.

DieselPlace.com is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 02-05-2019, 01:33 PM   #1 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

How to Adjust Passing Gear Kick-down?

I have a freshly rebuilt (3,000 miles) 4L80 behind my "new" 6.5L in my 1995 Chevy Step Van motorhome conversion. Engine and transmission both run great.


I drive >90% on highway at almost WOT. My only complaint is that when I "floor it" while cruising at 70mph to pass, or when I hit a hill, it jumps down into passing gear too easily.


I have the TPS adjusted properly. I figure if I adjust it counter-clockwise to minimize voltage at idle (0.5V? I forget exact number), then the high speed voltage is also minimized. I assume when the computer senses high voltage from TPS, it is thinking I need passing gear. So, I try to keep it adjusted counter clockwise to keep the WOT voltage low. However, if you go too far, you get a Code 22 (low TPS voltage at idle).
Turning idle speed up a bit helped this, but I just need to take a little sensitivity off the passing gear kick-down. When I had Code 22, it would not kick-down at all and I liked it - could keep pedal mashed without kick-down - however, it also keeps TC from locking up and fluid temp got very high.


So - how to "trick" the TPS into sending lower voltage at WOT, but not at idle? OR - do I have this all wrong?

OR - is there a wire I could tap into to put in a switch to disable kickdown? Would that affect normal downshift (like when slowing down)?

__________________
1995 Grumman P30 6.5L

Last edited by OkDually; 02-05-2019 at 02:23 PM. Reason: prefix
Offline  
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 02-05-2019, 03:01 PM   #2 (permalink)
johnH123
Diesel Apprentice
 
Join Date: Jun 2018
Posts: 334
iTrader Score: 0 reviews

The computer controls the shifting of gears, so in order to adjust shifting in anyway you need to adjust the shift points with a tune or something similar.

If I understand you right, you run at WOT and you think it goes to passing gear to easily? why are you running at such high rpm? how fast are you going? With a 4.10 rear end, i'm at 2000 rpm at 60mph.

The TPS is used by the computer to see when it needs to go to passing gear- a sudden WOT hit to the gas pedal triggers it to shift to passing gear. If you are running/cruising at wot and you need a little boost up a hill or something the computer will not know the difference between needing passing gear and your cruising.

Again, something seems wrong. Are you not getting into 4th? in 3rd gear with TCC lockup my RPM is at 3000 at 60 mph.

__________________
1993 K3500- 4x4, single cab/long bed, single rear wheels, 4.10 rear end, F vin, GM3 turbo, Nv4500 manual with Luk clutch and single mass conversion, factory red interior.

A few mods: 3" straight pipe, Bosch boost gauge, Bosch glow plugs, Draw-tite class 5 hitch.


Gone but not forgotten: 2001 silverado 2500hd CC/SB, 4x4, 6.0 vortec, 229k miles when I traded it.
Offline   Reply With Quote Quick reply to this message
Old 02-05-2019, 03:21 PM   #3 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

I am not really running at WOT all the time on level ground. No tach. I'd say though at least 7/8th throttle to cruise at 75 mph in 4th. If I press it to floor suddenly from there, it will kick down. OR - if I come to a hill and truck starts to slow - it will kick down. I believe all is well and running as supposed to- just not to my liking. I believe the computer (which controls ONLY the transmission) looks at voltage from TPS to guess my intentions (to go fast) and compares to speed sensor. I want to reduce voltage to computer if possible (I think).


Yes, it could possibly be reprogramed to accept a higher voltage, but I wouldn't know how to do that. Maybe vehicle was never designed to cruise over 75?


My high profile vehicle is VERY sensitive to air turbulence. I can go 85 in heavy traffic, but barely 73 sometimes on flat calm days.
__________________
1995 Grumman P30 6.5L

Last edited by Still Bill; 02-05-2019 at 03:22 PM.
Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 02-05-2019, 06:37 PM   #4 (permalink)
johnH123
Diesel Apprentice
 
Join Date: Jun 2018
Posts: 334
iTrader Score: 0 reviews

so you have a standalone controller?
__________________
1993 K3500- 4x4, single cab/long bed, single rear wheels, 4.10 rear end, F vin, GM3 turbo, Nv4500 manual with Luk clutch and single mass conversion, factory red interior.

A few mods: 3" straight pipe, Bosch boost gauge, Bosch glow plugs, Draw-tite class 5 hitch.


Gone but not forgotten: 2001 silverado 2500hd CC/SB, 4x4, 6.0 vortec, 229k miles when I traded it.
Offline   Reply With Quote Quick reply to this message
Old 02-07-2019, 09:09 AM   #5 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

Quote:
Originally Posted by johnH123 View Post
so you have a standalone controller?

Just the stock vehicle computer, but there are no sensors for engine, so it just controls transmission.
__________________
1995 Grumman P30 6.5L
Offline   Reply With Quote Quick reply to this message
Old 02-10-2019, 06:16 PM   #6 (permalink)
johnH123
Diesel Apprentice
 
Join Date: Jun 2018
Posts: 334
iTrader Score: 0 reviews

So just to verify, it is the stock computer in the factory location and the factory harnesses?
__________________
1993 K3500- 4x4, single cab/long bed, single rear wheels, 4.10 rear end, F vin, GM3 turbo, Nv4500 manual with Luk clutch and single mass conversion, factory red interior.

A few mods: 3" straight pipe, Bosch boost gauge, Bosch glow plugs, Draw-tite class 5 hitch.


Gone but not forgotten: 2001 silverado 2500hd CC/SB, 4x4, 6.0 vortec, 229k miles when I traded it.
Offline   Reply With Quote Quick reply to this message
Old 02-10-2019, 07:05 PM   #7 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

Quote:
Originally Posted by johnH123 View Post
So just to verify, it is the stock computer in the factory location and the factory harnesses?

YES, correct.


I might add that I had old tranny rebuilt when I replaced engine last year. Before that, it mostly ran so that it would never kick-down into passing gear. One day, it started suddenly to have a passing gear. That would last until next trip then mysteriously disappear. It would come back from time to time. It behaved EXACTLY like it does now with new engine and rebuilt tranny. I did not like it then when it would happen because downshift was too sensitive.


Most of the time it would not kick-down (for long periods - weeks or months), and if I actually needed it, I could do it manually (4th to 3rd). With my new engine and rebuilt tranny, I initially had TPS set wrong, and it had no passing gear, and showed code 22. Now, I know it probably used to run for long periods with code 22 (which doesn't show a light). However, that also keeps TC unlocked, and it runs very hot (I thought the heat was normal back then). It runs much cooler now. I added a temp sensor on outlet line when I swapped.

BUT - it is still too sensitive for my liking. I actually think it is 100% normal - I just want to change it. I can actually "feel" when it's just about to downshift and let up slightly, but my son is completely lost when he tries to go above 70.
__________________
1995 Grumman P30 6.5L

Last edited by Still Bill; 02-10-2019 at 07:09 PM.
Offline   Reply With Quote Quick reply to this message
Old 02-11-2019, 04:35 PM   #8 (permalink)
johnH123
Diesel Apprentice
 
Join Date: Jun 2018
Posts: 334
iTrader Score: 0 reviews

If you are in fact running at WOT there is something wrong. You need to get a tachometer and see whats going on.
__________________
1993 K3500- 4x4, single cab/long bed, single rear wheels, 4.10 rear end, F vin, GM3 turbo, Nv4500 manual with Luk clutch and single mass conversion, factory red interior.

A few mods: 3" straight pipe, Bosch boost gauge, Bosch glow plugs, Draw-tite class 5 hitch.


Gone but not forgotten: 2001 silverado 2500hd CC/SB, 4x4, 6.0 vortec, 229k miles when I traded it.
Offline   Reply With Quote Quick reply to this message
Old 02-11-2019, 06:11 PM   #9 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

Why do you think something is wrong? Seems like 80mph at WOT is faster than originally designed for a fully-loaded delivery van with high wind resistance. How fast should it go flat out? Seems to run great except that annoying passing gear.


If I get a tach, what will that tell me, other than my rpm?
__________________
1995 Grumman P30 6.5L
Offline   Reply With Quote Quick reply to this message
Old 02-19-2019, 04:18 PM   #10 (permalink)
Still Bill
Glow Plug
 
Join Date: Nov 2015
Posts: 254
iTrader Score: 0 reviews

I realized that I did not actually mean I was cruising at WOT. On flat ground, with no traffic, smooth road, and no head-wind, I can cruise about 72-75mph with about 7/8ths pedal. However, when I floor it to pass, or compensate for a hill, it kicks down and I can actually lose momentum/speed rather than gaining speed with extra throttle.


On my 500 mile round trip last weekend, truck seemed less prone than usual to do this. In fact, a couple times, it mysteriously didn't do it, but at those times I was really moving (80mph), and perhaps was closer to WOT, so that the increased throttle by flooring it did not kickdown.


The bit of extra speed may have come from replacing the fuel pump? Or maybe that road was just extra smooth.


Truck (Step Van) is VERY sensitive to air turbulence. Easily get 10 mph in traffic compared to pushing still air. The "bow wave" from passing (or trying to pass) a semi can be frustrating.

__________________
1995 Grumman P30 6.5L
Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Diesel Place : Chevrolet and GMC Diesel Truck Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

PLEASE READ! You must check your email inbox for the confirmation link to complete registration. Please check your spam box if you do not see the email in your inbox.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in


Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
4l80e shifts same tps plugged in or not no OD no passing gear ryobie1 4L80/85E Transmissions. 6L90 Transmission 19 12-18-2018 03:36 PM
Passing gear kick down Justis 4L80/85E Transmissions. 6L90 Transmission 1 10-18-2018 01:34 PM


All times are GMT -4. The time now is 10:42 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide