Question for you guys:

I have an 84 GMC 1500 with an almost brand new motor in it, and a trans that is bad. I found a 97 3/4 ton gasser with a blown motor and newly rebuilt transmission.

I took the motor out of my 84 and tossed it in the 97, but my question is, how do I adjust the transmission (4L60E) to shift out at a lower shift point so that it doesnt try to over rev my engine? second, how do I keep it from shifting from 4 to 3 when I go past 60, is there anyway to disable it so it doesnt downshift when Im hauling a trailer? All it does is get up to 60, I give it a little more pedal, and it downshifts and tops out the RPM on my poor engine and slows me back down to 50 again. I know I have a lot more power, but I have zero power when the trans kicks down like that.

 

you need the diesel torque converter and somehow get a diesel ecm that will control a 4l60e. Give Kennedy Diesel or Heath a call they MIGHT be able to help you with that. The 4l60e (as far as I know) was not offered on the diesel and you've got gasser shift points right now.
The 4l60 was not designed for the torque of the diesel, but I'm not the guy that will tell you it absolutely won't hold up. Ideally you should get a 4l80 (not E) out of a pre 95 6.5, but since your just kinda doing a no-budget build I'm guessing your not wanting to go that route.

 

yea, since this IS a 3rd vechicle, I dont see spending too much cash on it.

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Ok, I ID'd the trans wrong. I just looked it up and the truck came with a 4L80E. So would the same apply? I still need a diesel torque converter and an ECM?

Sorry, all my engine swap knowledge comes from cramming a small block chevy into a 4 cyl body of some type, I'm just learning all the diesel stuff...

 

How does the kickdown work on the gasser trans? The other problem I foresee is that the diesel with 4l80e is drive by wire, so I believe the kickdown is controlled by the ECM.
I guess if the gasser was using the TPS for kickdown and the diesel uses the same pin and resistance values from its TPS for the kickdown, it seems like it might work.
There's gotta be a way to make it happen, hopefully its easier than the harder ways. I'm up too early to be too creative but I'll try to get back to it when I actually get up.
At the moment my best suggestion on someone to ask is heath. They do westers tuning and know the computers.
Another idea I just had is to get that gasser ECM flashed with diesel shift points and pop the diesel TC on it. I have no idea where to get it done or how much it would cost, but it is an option. A standalone controller is also an option but they're spendy.

 

Well I think Im in luck. Found a guy on ebay that says he can just power tune (reflash) the existing TCM to match the 6.5 liter diesel for the same make and year and it should be perfect. Not too bad for 55 bucks and return shipping. I thought I was going to have to buy one of those aftermarket programmable TCM's - wow, pricey!

 

awesome man.
I'd still get the TC if budget allows for the right stall speed.

 

yah, it'll save fuel around town for sure, might not have as much pep as the gas TC tho