Hard Shifts After 4-Wheeling

[mayvillain]

I bought a 2002 Silverado 2500HD (8.1/Allison) in March, 135,000 miles. Love this truck.

Went on a somewhat unplanned 4x4 adventure in Bishop, CA. During a very long, very steep climb in 4x4 High, I noticed the Trans Temp got to 250; highest I've ever seen it. I pulled over and cooled off and it never got above 205 the rest of the trip.

Returning to town a couple days later, I noticed my first shift (1 > 2, if I recall) on the paved road was a bit jarring. Then, coming to a stop at a red light, an extremely rough shift as I came to a full stop. This happened twice.

I noticed the trans fluid was low, just within the Cold hashmarks with the truck at full temp. I topped if off with Dex 6 to the proper level (used Dex 6 because I wasn't sure what was in it). I haven't had any hard shifts since then. I am planning to service the transmission with this package ASAP:

Allison Service Package, 2001-2019 LB7/LLY/LBZ/LMM/LML/L5P

Service the Allison Transmission on your 2001-2019 Chevy Silverado/GMC Sierra 6.6L LB7/LLY/LBZ/LMM/LML/L5P Duramax with our Allison Service Package. These kits provide the correct amount of fluid and spin on external filter for 2001-2019 Duramax diesels using standard or deep Allison...

dmaxstore.com

Any cause for concern or advice for me?

 

[99Sierra2500]

Personally I'd service it, and keep an eye on it.

 

[ORVietVet]

Just adding fluid helped and there must be a leak. Do a service with filter and cross your fingers. How long since last service? Get any info when bought?

 

[Harry Dawg]

Not to make you paranoid, but the first symptom of my 4L60E nearing the end was a hard 1>2 or 2>1 shift coming to stop.

It was nothing crazy, just enough to notice it. This went on for like 2 years.

Then there was one instance where I was making a long drive on a hot summer day. Near the end of the trip I had a shift where it about knocked the head unit insert out of the dash.

It only did it once, but I knew I was in trouble. It lasted about 3-4 months before it gave up the ghost on a 4wheeling trip.

It was a 1>2 shift, and instead of shifting it just clanged... The sound was like when a U-Joint breaks.
I immediately turned around and headed home. Interestingly enough, it drove fine back to the house. It wasn't until the next morning when I left for work where it would just grind instead of shifting.

Makes me wonder what actually causes this phenomenon? How can an electronically controlled transmission have intermittent shifting failure?

As best I can figure, it may be an issue with the servo or the clutch packs have just enough material to give a couple more shifts after a major failure.

All of this being said- maybe if I had serviced the transmission when I first started noticing issues, the outcome would have been different.

Best of luck... Hopefully your tale ends with "I serviced it and it never gave me issues again"

 

[ORVietVet]

Not to make you paranoid, but the first symptom of my 4L60E nearing the end was a hard 1>2 or 2>1 shift coming to stop.

It was nothing crazy, just enough to notice it. This went on for like 2 years.

Then there was one instance where I was making a long drive on a hot summer day. Near the end of the trip I had a shift where it about knocked the head unit insert out of the dash.

It only did it once, but I knew I was in trouble. It lasted about 3-4 months before it gave up the ghost on a 4wheeling trip.

It was a 1>2 shift, and instead of shifting it just clanged... The sound was like when a U-Joint breaks.
I immediately turned around and headed home. Interestingly enough, it drove fine back to the house. It wasn't until the next morning when I left for work where it would just grind instead of shifting.

Makes me wonder what actually causes this phenomenon? How can an electronically controlled transmission have intermittent shifting failure?

As best I can figure, it may be an issue with the servo or the clutch packs have just enough material to give a couple more shifts after a major failure.

All of this being said- maybe if I had serviced the transmission when I first started noticing issues, the outcome would have been different.

Best of luck... Hopefully your tale ends with "I serviced it and it never gave me issues again"

I have over 172k on my 4L60E and am waiting for the problems.