Help please gmc 3500 blown 4l80e

[Johnpettersen]

Good day all, I'm in a bit of a jam, covid has left me broke and frazzled!
My transmission failed in my 96 gmc 3500 1 ton dually extra cab I foolishly purchased a rebuilt trans for 900 bucks with a 1 year warranty, the guy who built the tramsmission, the transmission and the warranty all rank in the P.O.S. category, I certainly was hoping for a lucky brake due to my covid induced situation, no luck at all ! Any way that's the story now I'm trying to make the best out of it (it is what it is rite!) So I don't have the funds needed to repair either of the two 4l80e's i now have, my original that was supposed to be given as a core and the pos I bought for 900 ( fat chance he was going to get my core )
So I will rebuild the trans which I purchased which is a late model with the return cooler fitting at the rear of the housing and between the two I have enough hard parts to build a good unit unfortunately money is more than small issue at this time so my thought is, this is the hard part knowing how stupid this will sound,,,, and how much crap I will catch for asking such a question, a very generous person is offering me for free a 700r4 that is rebuilt goodwrench, I drove the wrecked truck its in and it works flawlessly, until of course I can fix the 480le I have a mig and a plaz so fabrication is not a concern, my concern is #1) my truck has a 454, is there a torque converter available for the 700 which only has 3 ring gear mounting lugs compared to the 454/4l80e's with twice as many #2) the down grading of the wire harness ten pin to 4 pin I didn't see a t.v. cable on the 700 but I may need to deal with that as well I'm not sure if there is one or not and of course the really lucky thing is my truck is 2wd and the 700 is out of a 4wd with t case attached oh joy more fun! I have no intention of making mine 4wd it just needs to go 100 miles round trip to work and home reliably
Any insight on what might be needed other than ridicule and abuse would be greatly appreciated! I'm am well aware of how stupid this conversion is and the difficulties I may indure, however determination perseverance and a little help from my fellow man, hopefully will get me back to work so I can eventually get the 4l80 built and the cobbled up mess removed
Thanks for reading and any positive input is certianly appreciated!
Sincerely John p

 

[Wes Harden]

Flex plate torque converter shouldn't be an issue the 700r4 should bolt to your flex plate.
That said, 700r4 does have a tv cable, 4l60e does not. Basically the same trans, similar to the 4l80e.
Not matter which the free trans the truck computer is going to have a fit.
Then there is drive shafts to consider.
I would leave the t case since temporary use donor truck cross member, and pray that donor drive shaft will work.

Is a tough call there will other little pita things to sort out.

 

[Johnpettersen]

Thanks for the prompt response I will use the slip yoke off of the 700 and cut the shaft to fit, the dually is long bed with a carrier brng so I believe I have the drive line covered with only minimal welding and the switch back will be easy just a quick cut of the weld on the lathe and the drive line back as it was, I amconsidering using the existing gmc ecu and reflashing it to only see the necessary inputs vss tps tcc ect. To keep it simple for the change back to oe and not have a check eng lamp illuminated I'm not to hip on the domestic cars but loads of experience on the jap stuff I've put a few lexus v8's in 4 runners and such, so a reassuring kind suggestion makes things seem more doable tomorrow I'll see if the ring gears will swap the 700r4 has a v6 hopefully they swap or possibly 3 of my six may line up I didn't see a balance weight on the 454 rig gear but it fitting is wishful thinking on my part

 

[Wes Harden]

The V6 is 4.3? Uses same flex plate as 5.7/350. But I'm pretty sure the bolt circle on 6 bolt converter is the same as 3 bolt

 

[imiceman44]

The V6 is 4.3? Uses same flex plate as 5.7/350. But I'm pretty sure the bolt circle on 6 bolt converter is the same as 3 bolt

It is

 

[Blue85]

How about rebuilding the 4L80? If hard parts are needed, the 2nd unit may have them. For just seals and clutches we're talking just hundreds of dollars, not thousands. May be less work than all the mods needed to install the wrong trans - especially because that may have to be reversed someday.

 

[sweetk30]

x2 above . . . jumping over a dollar to save a penny .