4L60e, transcooler line burst and lost reverse

[project_x]

I picked up a used 2003 Suburban Z71 4x4 that burst a line or trans cooler before I bought it.
The transmission had about 35,000 miles at that point...
It still has all forward gears... But reverse sliiiiips (need to put it 4Lo to move anywhere).

I'm pretty sure I know the answer.. but the only way to investigate this is by pulling the trans(there no things that can be checked on the truck)? And what is the likely hood it doesn't need a full rebuild?

Should I just pull the trans and swap in a known good 4l60/4l65 or bite the bullet and do a 4l80 swap?

 

[Joseph Garcia]

@NickTransmissions is our resident transmission expert, and he will chime in with his thoughts and perspectives.

 

[NickTransmissions]

I picked up a used 2003 Suburban Z71 4x4 that burst a line or trans cooler before I bought it.
The transmission had about 35,000 miles at that point...
It still has all forward gears... But reverse sliiiiips (need to put it 4Lo to move anywhere).

I'm pretty sure I know the answer.. but the only way to investigate this is by pulling the trans(there no things that can be checked on the truck)? And what is the likely hood it doesn't need a full rebuild?

Should I just pull the trans and swap in a known good 4l60/4l65 or bite the bullet and do a 4l80 swap?

Drop the pan, look for burnt clutch material at the bottom and see if any of three the reverse hold-down plate bolts (8mm) are loose...It's highly unlikely unless the unit was recently worked on and spacer plate removed for some reason (i.e. to install a shift kit or repair/replace the plate). If they're not loose, put the pan back on w/a few bolts and yank it for overhaul.

Apart from your Z71 putting out more than 500 crank HP and/or you use it to tow/haul in excess of 7,000 lbs you do not need a 4L80E. A properly rebuilt 4L60E will last you a very long time under normal usage patterns/conditions.

 

[project_x]

Thank you

 

[noodlesandsam2]

Debris from the last blown unit is what worries me. Or the build was no good. My 2001 1500 with 4L60 / LM7 5.3 went to the boneyard with nothing but fluid and line changes. 270K. I now have a 4L80 - they do feel different.