GM 4L80E Transmission Shop in Daytona FL

Broke an input shaft on a T400 last year on the race car I drive. Like I said, it doesn't happen often but it does happen. But yet again a 572 puts out a bit more power than your tow rig. :)

You're 4L80 should give you many years of service when rebuilt correctly.

Thanks for the info/ideas. Dealer (where it was orig. towed) only does remans ($3800 - ouch) & so had it towed (for free :) ) to Aamco (we wanted a warranty good anywhere since we travel so much). They tore down and found that the steel shaft had split in two. He said that he almost never sees that - lucky me, I guess. Anyway, $2400 to repair/rebuild w/ 1yr/12 mo. warranty so I went with a reman unit instead for $300 more for a 3 yr/50,000 mi. Warranty. That should keep us out of trouble for a while. Thanks very much to Don for all the offline help. He, and all of you always help me go from clueless to informed in no time flat. I appreciate you very much. Now we're $2700 poorer, and added 5 days to our 30 day camping trip (we were almost home!!!) but we're thankful to be alive & safe. The loss of ability to accelerate in the middle lane of I-95 while towing could have ended much worse.

A spraqe is not an easy fix the valve body gets pulled, pump drums etc. if your going to go that far might as well do the job right and rebuild it with updates and shift kit. Depends how long he plans on keeping the truck. Stuck in nuetral is unlikely unless the linkage is not stroking the manual valve inside the trans. Sounds like something internal broke. If that's the case do not reuse the old trans cooler, add an aftermarket external one a flush will not get all the metal out and it will get sent back into new trans, and do not reuse old convertor the same reason.

Check with AAAccurate in Ormond/Bunnell. Big Rigs on down. By 95 and US-1.

What you are describing sounds like the planetary gear assembly may have cracked. Was there any noise ?

4johnsonsandadog wrote:
Dealership just called and told us we needed a new transmission. That it was an "internal component" and cannot diagnose exact problem w/out tearing down. New tranny $3800. Ugh. Please advise.

4johnsonsandadog got a reman quote from Aamco at $2700, $1100 cheaper than the dealer, with 3 yr 50k mile warranty vs dealer's 3 yr 100k mile warranty. Plus Aamco is willing to take it apart and see if it's fixable vs just replacing the entire unit. We may get a post-mortem on this if they go that route for repair.

Unfortunately mine didn't get opened so not really sure what went wrong. The Jasper unit runs and shifts just like a brand new one. Even makes the same noises and whines at the same frequency at the same speed LOL...Jasper warranty is 3 yrs and 100k miles but was around $3500 IIRC. Had to do a mandatory fluid/filter change at 5k miles to replace the "break in" fluid, so used Dex VI and it's going strong.

my guess is valve body and stuck in 'N'...so no ATF going through the TC

How many miles and what do you tow?

Chipped?

My 4L80E is now at around VERY, VERY HARD 162,000 miles...know it's only matter
of time...

Don, how do you like your Jasper?

My 7.4L is also showing it's age...no longer an easy beat'm up on
the boulevard...yeah, still have that boy racer in me...

A mechanic friend I spoke to when we first broke down just possibly gave me another piece of puzzle. When we had him on phone on side of road, he had us check tranny fluid and describe level to him. He said the level was higher than it should have been w/motor running. That ruled out an electrical issue, I guess. Does any of that shed any new light on what broke?

4johnsonsandadog wrote:
Dealership just called and told us we needed a new transmission. That it was an "internal component" and cannot diagnose exact problem w/out tearing down. New tranny $3800. Ugh. Please advise.

Well that sucks. I was going to say it was going to be a big failure like an input shaft or something of that nature or it was going to be something simple like a wire issue.

The 4L80 is a great tranny. Tough tranny, but things happen. Sorry to hear about your problems.

Get a new tranny and go on with life and vacation.

PS, I would have them tear into it before they get a new tranny. A sprag might have blown and things like that are easy to fix.

Dealership just called and told us we needed a new transmission. That it was an "internal component" and cannot diagnose exact problem w/out tearing down. New tranny $3800. Ugh. Please advise.