Texas82GP's GMT900 4L80E Swap

Texas82GP

Texas82GP

Comic Book Super Hero
Supporting Member
Apr 3, 2015
4,870
113
Spring, Texas
A little less than two weeks ago the transmission went out on my daily driver. It's a 2008 GMC Sierra 1500, regular cab, short bed, two-wheel drive with a 5.3 and a 4L65E transmission. The 4L65E has been built twice in the last 50k miles. It has some nice goodies inside it but I keep finding its weaknesses the hard way. When it went out two Wednesdays ago, I had asked it to complete one too many 1-2 upshifts at WOT. It broke the output shaft. The 5.3 in my truck is no powerhouse by today's standards. My guess is maybe 400HP, maybe 400 ft. lbs. It has the stock intake and heads, has a LS3 throttle body, an underdrive pulley, long tube headers and a GM LS Hot Cam. Still, it and me seem to be too much for the 4L65E. It would probably be cheaper to fix the 65E but I've decided to move on and swap to a 4L80E. I had the truck towed out to my storage where I keep the GP. I started the search for a replacement transmission and started doing my homework on the swap. The following weekend, I spent Saturday with Dad cleaning up the shop. It was a wreck! I had been just going over there and setting stuff down on the bench for a year. The engine hoist was still assembled. It wouldn't have been that big a deal but it is a 14'x40' storage and it was difficult moving stuff around in there with the truck and the Grand Prix both in there. It was a rainy day and there is a bit of an incline up into the storage so I didn't want to roll the truck out for fear of Dad and I not being able to get it back in on our own between the wet pavement (shoes slipping), dad's age, and the fact that with the broken output shaft the truck didn't like to roll much whether it was in neutral or not. Still, by the end of the day on Saturday, the shop was whipped into shape and the truck was on stands.....

20190222_172957-2016x1134.jpg


Someday, baby.....

20190222_173032-2016x1134.jpg


I was able to make it over there one night the next week, which was last week and start the tear down. I got the driveshaft pulled and most of the exhaust Y pipe but it got late on me and I had to pull off. When I pulled the driveshaft, my suspicions of a broken output shaft were confirmed....

20190218_201721-2016x2688.jpg


In the meantime I did a lot of shopping around looking for a core. I have a good friend who manages an automatic transmission parts house. He put the word out looking for a core. I hunted on eBay, Car-Part.com, Craigslist, etc. I stopped at a few junkyards between work and home. I searched the inventory online for the local Pick-A-Part yards. Last Wednesday, I settled on a 4L85E out of 2009 3500 van with a diesel. It had a little over 117k miles on it and the vehicle had come off the road because of a wreck. Here is a look at the donor vehicle..

s-l500n.jpg


s-l500.jpg


s-l1600.jpg


The transmission was in Mobile Alabama. I bought it off of eBay. I bought it on Wednesday, it shipped on Thursday, and was on the dock at the freight terminal on Friday. I picked it up Friday evening with a friend and we hauled it to the storage....

20190222_171418-2016x1134.jpg


20190222_171442-2016x1134.jpg


20190222_171528-2016x1134.jpg


I paid $900 shipped. I know that isn't a good used 4L80E for $500 but I'm happy with it. It's the latest design of an 85E (heaviest version). It's relatively low miles. It came with the lower bellhousing and shift cable bracket. It looks to be in really nice shape. Instead of spending Saturday hitting the junk yards looking for a core, I was taking the 65E out of my truck. It was worth it to me.

Before pulling the transmission, I pulled the pan to get as much fluid out as I could. What I found didn't look pretty....
20190223_115932-1134x2016.jpg


20190223_115940-1134x2016.jpg


20190223_115946-1134x2016.jpg


This just reinforced that the 65E just isn't enough transmission for me or the warmed up 5.3. My buddy thinks the rear planetary may have been on the way out, looking at the long steel shavings.

Saturday, Dad came over to the storage and helped me pull the 65E. For you guys who haven't seen the Harbor Freight transmission jack in action, here you go....

20190223_151447-1134x2016.jpg


If you don't have one, consider getting one. I think its the best thing they sell. You can pull/install the transmission by yourself with one of those.

And here they both are on the ground....

20190223_160929-2016x1134.jpg


I had recently noticed some oil seepage on the back of the oil pan and front lower edge of the bellhousing. I suspected the rear main seal, so at this point I pulled the flexplate. Looks like it has been leaking a bit.....

20190223_164509-2016x1134.jpg


This engine has 170k miles on it. I'm going to go ahead and replace the pan gasket, rear cover gasket and rear main seal while I'm in there. I plan to do that on Saturday. I haven't decided if I'm going to have the 85E rebuilt or not. I may just put a shift kit in it and go with it. I won't decide until I get it on a stand and pull the pan. That's it for now gents. Hope you enjoyed it.

Best,

Jared
 
DRIVEN

DRIVEN

Geezer
Apr 25, 2009
5,809
113
Owyhee County
How much external parts replacement will be necessary? It's not just a simple bolt-in swap, is it?
 
  • Like
Reactions: Texas82GP
-83MONTESS-

-83MONTESS-

Moderator
Moderator
Nov 4, 2010
4,538
113
Bellevue, Ohio
Im tuning in for this one. I have an 07 with the even weaker 60e. I have always wondered what it would take to go to an 80e when this one Pearl Harbors itself.
 
  • Like
Reactions: Texas82GP
Texas82GP

Texas82GP

Comic Book Super Hero
Supporting Member
Apr 3, 2015
4,870
113
Spring, Texas
How much external parts replacement will be necessary? It's not just a simple bolt-in swap, is it?
It's not awful. It requires a torque converter if you don't want to use the one that comes with the (presumably) used transmission core. It requires a different slip yoke but the driveshaft is fine since the overall length of the two transmissions is the same or very close. Both the 4L65E and 4L80E slip yokes use 1350 series U-Joints so it is a direct swap. It requires a different dipstick and tube, which are still available new. You want to get the lower bellhousing with your transmission as it is around $100 to buy new. You also want the shift cable bracket to come with the transmission core but it is available and not too expensive. You don't have to change the flexplate since you can get a converter set up for the 5.3 flexplate and the 4L80E. I went ahead and got a 6.0/4L80E flexplate since it isn't expensive and I wanted 6 torque converter bolts as opposed to the 3 that is stock to the 4L65E setup. There is a little bit of wiring. You have to re-pin two wires in the main transmission connector. Also, the 4L80E has two speed sensors, where the 65E only has one. Consequently you need to run two wires from the front speed sensor up to the Transmission Control Module (separate in my truck) and pin them into the harness. Then you need to have your tuner segment swap the 4L80E program into your TCM and tune it from there. The transmission cooler lines need some reworking or replacing. I haven't decided what I'm going to do on this yet. I may run AN hose but I may bend/flare my own new hard lines. Then there is the crossmember. On a 2wd application, the mount moves back 6" relative to the 4L65E so crossmember modification is required. I may have to rework my catalytic converter/Y-pipe assembly as well. It likely won't fit with the 80E. I have long tube headers from Dynatech. When you buy them, they offer an "off-road" Y-pipe or they offer a converter/Y-Pipe assembly that includes two converters, and the Y-pipe. It comes in three pieces. I've never been happy with how it fit. It is good at banging on the transmission crossmember so I won't be heart-broken to re-engineer the portion of the exhaust from the header collector to the extension pipe from the muffler.

I guess there is a lot to it. Still, I have a place to work on it and have something to drive while I do. I'm glad I decided to go this route because the truck will be much better for it. I bought this truck new and am keeping it. I don't like the uppity nature of today's new cars so the likelihood of me buying anything newer than this truck is remote.
Glad to have you along Joe. Hopefully I can keep it interesting.

Im tuning in for this one. I have an 07 with the even weaker 60e. I have always wondered what it would take to go to an 80e when this one Pearl Harbors itself.
Welcome aboard. The 4wd swap is a bit more complex but if you search around on the threads, they have it all figured out. All you have to do is look at the size of the puny output shaft on the 60/65/70E and you realize that it should never have been put in a truck. In fairness, it's fine in a stock application but not for anything more than that.
 
Texas82GP

Texas82GP

Comic Book Super Hero
Supporting Member
Apr 3, 2015
4,870
113
Spring, Texas
Small update. I dropped off the driveshaft yesterday morning and picked it up this morning. As I mentioned above, the two transmissions are the same overall length so all that is required is a yoke swap. I sourced a 4L80E yoke online made by Spicer. They offer a short and a long. I bought the long to match the length of the yoke on my stock driveshaft. I could have done the swap myself but the factory U-Joints aren't greasable and mine have 170K miles on them. I wanted new Spicer U-Joints. I spent $150. They swapped the yoke and U-Joints, balanced it and painted it. It's ready to go in.

20190226_085137-2016x1134.jpg


That's it for now gents. I'll update when there is more progress to report. Thanks for the interest and the likes.

Best,

Jared
 
8

81cutlass

Royal Smart Person
Feb 16, 2009
1,779
113
Western MN
Any reason you went with a 80e vs a 6L80e considering you have an NNBS pickup?

I know not all 09+ NNBS GM's got a 6 speed but since it was a factory option just curious your reasoning.
 
  • Like
Reactions: Texas82GP
-83MONTESS-

-83MONTESS-

Moderator
Moderator
Nov 4, 2010
4,538
113
Bellevue, Ohio
Any reason you went with a 80e vs a 6L80e considering you have an NNBS pickup?

I know not all 09+ NNBS GM's got a 6 speed but since it was a factory option just curious your reasoning.
I can't answer for the OP but from my reading-light at that-the 6L80e has more problems than the 80e, and the gear spread isn't much different. Ironically I learned this when doing the research for the OD transmission I want to end up with in the aerocoupe.
 
  • Like
Reactions: Texas82GP
motorheadmike

motorheadmike

Comic Book Super Hero
Nov 18, 2009
3,881
113
Ottawa, Ontario Canada
Uh oh! I am seeing a little bit of "since I am in there anyway..." going on.

Good ol' project creep. ;)
 
Thread starter Similar threads Forum Replies Date
Texas82GP Non-G Projects 18
Similar threads
Mail order 4L80E?

Please support GBodyForum Sponsors

Classic Truck ConsolesDixie Restoration DepotMike's MontesP-S-TSouthside Machine PerformanceUMI Performance

contact[email protected]for info on becoming a sponsor