454SS 4l80e trouble

Big Jay · January 5, 2007

Hello, 1991 454ss 60.000km,never abused,owned since new.other day moving itout of my garage 1st gear seemed locked up(like fwd and reverse were fighting) 2nd was better but still felt not right like it was trying to stop the truck,3rd OD and reverse and N all ok.Any ideas on what tranny component or?????could be happening.I also have my hypertec chip installed,will put the stocker in just to see if it makes a difference.thanks JS

GM-Tech · January 5, 2007

Seems to me the 4L80"E" wasn't available until 92-93. You sure that the "E" is what you have? If not, the chip won't matter since the trans is not electronically controlled.

Sounds mechanical in any case, but I'm not a tranny guy.

Big Jay · January 6, 2007

Seems to me the 4L80"E" wasn't available until 92-93. You sure that the "E" is what you have? If not, the chip won't matter since the trans is not electronically controlled.

Sounds mechanical in any case, but I'm not a tranny guy.

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Yes I am sure the 91 454ss@800 built came with the 4l80e tranny.Thanks I will try the chip swap tomorrow!

ChevyTech007 · January 6, 2007

Sounds like it is starting out in 3rd gear. Check all fuses, if they are all good the most probable cause is the ignition switch. A loss of voltage to the trans is the problem.

mmmikkke · January 6, 2007

I'm pretty sure '91 some 2500's and 3500's had the THM400 trans, which is the 4L80E's predecessor. 3 forward gears, no locking torque converter.

In my '86 K20 C6P (HD), I had that trans. At about 50Kmi, the dowel holding in the reverse band drifted out and caused exactly what you've described, seeming binding up in the trans. After a few days, reverse was gone. Required a trans rebuild. Luckily, they did a nice job and the truck went 100K without issue after that.

redvett · January 7, 2007

You can tell a 4L80E from a 4L80 by the big wire harness on the drivers side of the trans by the shift shaft. The 4L80 has a TV cable on the throttlebody linkage.