4L80E Information Thread

[98gmc2500]

So based on your chart of transmissions, can I swap a 1999+ 4l80 with my 1998 4l80? And is there anything I should be aware of?

Thank you in advance

 

[NickTransmissions]

So based on your chart of transmissions, can I swap a 1999+ 4l80 with my 1998 4l80? And is there anything I should be aware of?

Thank you in advance

You can swap a 99 4L80E into a 98 vehicle.

As far as what you'd need to be aware of, I'd need a lot more information than what you provided. For example, why you're swapping transmissions instead of rebuilding the unit that is in there now (if in fact it needs to be rebuilt), how the vehicle (presumably a GMT400 HD truck) is currently being used and the like.

 

[98gmc2500]

You can swap a 99 4L80E into a 98 vehicle.

As far as what you'd need to be aware of, I'd need a lot more information than what you provided. For example, why you're swapping transmissions instead of rebuilding the unit that is in there now (if in fact it needs to be rebuilt), how the vehicle (presumably a GMT400 HD truck) is currently being used and the like.

The transmission I’m taking out started overheating (snapped cooling line) grinding and slipping, and rebuilding a transmission is a lot more expensive than what I can afford, my plan is to buy one to get me by a while longer till I can do something different like buy new or rebuild it or buy a reman, so I’m trying to figure out what year of 4l80s I can put in my truck.

Thanks

 

[NickTransmissions]

The transmission I’m taking out started overheating (snapped cooling line) grinding and slipping, and rebuilding a transmission is a lot more expensive than what I can afford, my plan is to buy one to get me by a while longer till I can do something different like buy new or rebuild it or buy a reman, so I’m trying to figure out what year of 4l80s I can put in my truck.

Thanks

Gotcha...If possible, keep your existing transmission - 4L80E 2nd design (center lube) cores are selling for $350-$400, at least here in Vegas and prob so in Michigan.

Another thing to be aware of is the 1999 transmission may have a bolt hole at the 12 o'clock position on the bell housing for LS engines - that doesn't matter as it will bolt behind your engine, assuming it's a Gen1 small block. Just keep your existing converter (or purchase a new, identical torque converter to the one that's on the transmission in the truck now.

Prior to installing the replacement transmission, do the following:
1. Replace the rear main seal if you haven't done so recently - that would be the time to do it
2. Check the flex plate over carefully for cracks or other signs of damage while it's off
3. Flush your transmission cooler lines, internal trans cooler in the radiator as well as any externally mounted trans cooler(s) so you remove all the contaminants from the system

I'd also replace the wiring harness on the new transmission...4L80Es are notorious for leaking harness that short out and put the trans into limp mode...I'd also replace the speed sensors AND pull the speed sensors off of your existing transmission and keep them in the truck at all times. Ditto for the manual lever position sensor (large black sensor on the side of the transmission over the selector)...Install a new one and keep the old one in the truck so you have spares that can be installed quickly if the new ones fail prematurely...