Weird drivability issues

[Chris_G1]

2007 for years has had a sluggish feeling most all the time from a stop, this feeling is exaggerated huge by pulling my trailer, from a stop up a grade i am almost foot to the floor to get reasonable momentum. It also for years has had a little transmission slip when shifting from 2-3….but only when pulling my trailer. Took it in to be looked at and the trans was given a clean bill of health

Years later its still doing it but now it’s also started to have a very random, very infrequent hard 1-2 shift. Never have had any check engine light come on, and because of the new 1-2 shift issue i do have an appointment to have it looked at but im not holding much hope for a find because there is no warning lights unless i get lucky and it happens on their test drive

i do stay regular on transmission oil changes, i have done 3 or 4 in the 125,000 miles on the truck

anyone experienced anything similar? The fact its been doing it for years makes me believe it’s incredibly minor, but I would love to find a solution. Minor or not im sure internal damage is happening somewhere

 

[MS03 2500]

What's your tranny temp running.

 

[EXT4ME]

The 4L65E in my 2004 EXT went out at 125K even while equipped with a factory aux transmission cooler.

I have had other GM trucks without an aux cooler go out as early as 85K.

The slipping from 2 to 3 is a classic failure symptom and that is what most of my failures were over the years.

If you have to get a transmission rebuild, plan to invest in a Tru-Cool 40K aftermarket transmission oil cooler to protect your new investment, especially if you tow.

 

[Chris_G1]

What's your tranny temp running.

Unfortunately I don't know, I have never checked that when towing my travel trailer. When I was pulling my little 5x10 enclosed trailer, no more than 1200lbs I was watching it and I don't recall it going over 200, and the symptoms were there with that trailer too.

The 4L65E in my 2004 EXT went out at 125K even while equipped with a factory aux transmission cooler.

I have had other GM trucks without an aux cooler go out as early as 85K.

The slipping from 2 to 3 is a classic failure symptom and that is what most of my failures were over the years.

If you have to get a transmission rebuild, plan to invest in a Tru-Cool 40K aftermarket transmission oil cooler to protect your new investment, especially if you tow.

I have read a few times about the 2-3 slip and I don't doubt it may be time......but the thing I find weird is that it's been doing it for years, only ever with the extra load of a trailer, empty the truck 2-3 shifts fine, also if I'm gentle with the throttle input towing the slip doesn't happen

An absolute long shot I thought of, I'm having some issues with my trailer brakes that I believe I have traced back to a bad ground, the ground location for the 7way plug is in horrible condition. Knowing again this is a long shot, but would bad grounding on the chassis grounds cause drivability issues?

 

[MS03 2500]

Sadly once the tranny starts to slip, there is nothing you can do except replace it. I would have thought your mechanic would have seen the code for it.

 

[Chris_G1]

Sadly once the tranny starts to slip, there is nothing you can do except replace it. I would have thought your mechanic would have seen the code for it.

It's going back next week to be looked at again, hopefully they find something. Last time a few years ago when I brought it in they kept it for 2 or 3 days and came up with nothing, said everything was functioning as it should be

There has never been any check engine light on and apparently no stored codes either

I'm certainly no mechanic , but i just find it odd that it's been happening for 3ish years and there hasn't been a total transmission failure. I completely understand once slipping starts it's the beginning of the end.....but surely the end isn't years and years away. I wouldn't think, this is my first experience with transmission concerns

 

[EXT4ME]

Transmission error codes may not necessarily cause a CEL, or Check Engine Light to illuminate.

While engine and transmission error codes generally both begin with the letter P for Powertrain, some of those error codes are out of the range of some scan tools.

One such error would be P0700 that indicates a problem with the transmission control system, which can cause engine stalling, poor gas mileage, and difficulty shifting.

It usually takes a more capable scan tool to read transmission error codes.

Any good transmission shop should have such a scan tool and also be able to read live data and be able to manipulate various functions of the transmission.