4L80E Transmission Teardown

S3700019

Well, although i have had this core for quite a while, i finally had the time to take the thing apart, document it, and most of all LEARN from it. this one in particular was a core out of a dumpster that i paid fair price for. it was missing the wiring harness and filter so basically what you see here is what i saw. basically the overall scheme of this tranny is a th400 with an overdrive unit glued infront of the front drum. the valve body is very similar to the same appearance and function of a 4L60 or even a 4R70W Ford. it is an aluminum valve body with a PWM, two shift solenoids, and a pressure switch manifold. what is absent though from the 4L80 that you find in the 700R4/4L60E is the TCC solenoid. the pressure regulator like the older th400’s is in the front pump. in addition there are also two TCC valves located in the front pump. i will get into detail on this a bit later, along with some model year stuff. unlike the 4L60’s and 4L60E’s, there isn’t as much info on these trannys easily found like there is on most others.

first thing to come off is the outer switches and cooler line fitting, specifically the rear cooler line fitting. there are two speed sensors to the left side of the case that you shoud remove to replace damage. also the shift position sensor. basically they moved it from the steering column to the side of the tranny and made the shift selector shaft longer. it has nothing to do with the internals of the tranny. you would also remove the rear cooler line fitting from the case. it protrudes into the center support and will make removing the rear planetary gearset damn near impossible. since the overdrive unit interrupts lubrication circuits that would have flowed similar to the th400, they re-routed the lube return fluid directly to the center support. anyways just don’t forget to remove the fitting.

After the pan and wiring harness removal,  the pressure switch manifold is next at this point. like the 4L60E, this is the signal manifold the connects to the ECM S3700022to let the on board computer know what the hell is happening in the tranny….and signal shift or set off idiot lights accordingly. it is help on by 6 bolts that go all the way through the valve body to the case and are an 8mm head. next is the clamp and steel lube line to the rear housing bushing and seal area. this is a 10mm bolt and clamp and is easily removed. anfter all that, you remove the rest of the valve body bolts and lift off the valve body assembly.

 

This leaves you with the valve body passage containing 8 check ballsS3700023, the low 2/front band servo, and you can also see the rear servo cover assembly like the th400 and center support bolt, but there is also a front support/fourth gear piston housing bolt as well. it is a torx head bolt.

 

 

 

 

 

hereS3700048 is a picture of the front bolt locationunder the valve body to be removed like the rear center support bolt on this tranny….and the TH400 trannys. at this time i would also go ahead and remove you rear servo assembly from the case so that there is no hardware left to interfere with the rest of tranny disassembly. the rear servo is VERY similar to the Th400 in that the rear band pin is an adjustment, but the piston, accumulator, spring, and cover are different. so don’t get the brilliant idea to interchange the parts.

 

Next, i pulled the tail housing. it is 6 bolts and although a similar pattern to a th400 tail, it is not the same. S3700028some of the 4L80’s used a tin oil shield like the older Th350 tranny’s did, some did not. they all had an internal oil seal thought. it may look like a roller bearing but it’s not. the rear bushing is actually smaller than a 400! if you have a tin shield it has to be removed, the seal does not. it can be removed and replaced later.

 

 

time for the front pump to come out.S3700026 first and foremost, remove the input shaft o-ring so you do not pull the guts out all over the shop floor. remove the pump bolts and like i do on the th400…..coax it out with a large screwdriver. pictured is what you should see. this is the front of the tubbine shaft/overrrun clutch assembly, and 4th clutch assembly to the outside of it. the center assembly pulls out like a forward drum assembly on a Th400. the 4th clutch assembly is held in by a snap ring and can be removed next.

 

the 4th gear clutch assembly housing/piston assembly can be removed and you are now down to the forward clutch. from here back it is damn near identical to the Th400 transmission. now although they may seem identical to the th400, not all the components of the aft assembly interchange. i will get into this in other articles. here you remove the forward drum, direct drum, low 2 bad, 4 disc intermediate clutch, and rear planetary/center support. the center support on these fits pretty damn tight to the case. they make a tool for removal, however i used a lead hammer and tapped it out of the case. i also used a big brass drift to coax it back home into the case during assembly. use good judgement when doing this if you are worried about it….don’t ram rod it!

Comments are closed.