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Re: new engines for the GMCs [message #316766 is a reply to message #316589] Sat, 29 April 2017 01:31 Go to previous messageGo to previous message
Hal StClair   United States
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma:
Senior Member
TR 1 wrote on Tue, 25 April 2017 08:33
Mike, I'm sorry if I came off as saying you were not capable of doing the swap. That was not my intention. My point in listing all that stuff out was to illustrate the point that engine swaps are a lot of work... And that the 455 and Cad 500 really are good motors for our application. You are 100% right, at some point we will NEED a new engine option... I also agree with you that the LS motor is the best gas engine out there right now for the job. But good god, it's a lot of work to get it in there and working, then add all the ancillaries as well...

But you are also correct in saying that the more options we have, the better off we will all be. I'll tell you, if I were going to do an LS swap on the GMC, and I needed to modify the interior anyway, I would probably look the possibility of using a 4L80 to get the extra gear and lockup converter.... I believe Hal's diesel setup uses a 4L80 or similar, and some sort of transfer case to get power back to the front...

Hal, could you maybe describe how your setup works?



Been out of town for a few days, sorry.
I used a 4l80e behind the H1 Hummer 6.5 with B/W transfer case I located from Revcon MH. Although the transfer case is all but impossible to locate today, one could use a NP205 TC which are easy to find and adaptors are readily available. I ran forward to a late model 9.25" AAM differential with custom built equal length half shafts. These front diff's are available from 2011 up 1 ton Chevy/GMC trucks. Ratios are somewhat limited with 3.73 the fastest offered from GM although a 3.42 was offered by AAM which is what I'm running now.
6.5's were never available with more than 4 speeds (auto's that is) as far as I know so any 6,8,or 10 speeds would have to be specially programmed and built to handle the diesels needs. A 4l80e can be modified to have 5 or 6 speeds but it's an expensive process which requires internal gear ratio changes to fully exploit the gear splits. A stand alone ECU would be required and you would loose the engine PCM's interface with the transmission which would probably cause drivability issues. The 4 speed with the locking convertor seems to work very well and with the diesels high torque at modest rpm's requires very limited downshifting.
Hal


"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane." 1977 Royale 101348, 1977 Royale 101586, Diesel powered, 1974 Eagle Bus 45',w/slideout, Rio Rancho, NM
 
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