4L60e and a 383

[LVJJJ]

3 years ago Bought our '94 GMC k1500 to tow our 28' TrailCruiser that only weighs 5,000 lbs loaded. Was a one owner, always garaged crème puff, however 350 sucked, still had original plugs, wires, cap & rotor at 126,000 miles. Would barely go 65 mph and wouldn't tow till I removed original air cleaner setup and ran two 4" cold air intakes, MSD adjustable timing control, Fastchip and dual exhausts. Still wasn't acceptable so just had a new 383 stroker installed. Can't believe the torque. Found that the new engine didn't like running a high rpms in 3rd while towing, so put in 4th and it just settled in and ran easy, didn't hunt or have to shift down or unlock torque converter until going up steep hills. (Burb is an SLE with complete tow package, trans & oil coolers etc.)

So, the question is, is that going to hurt the 4L60e? Shifts good and didn't get hot on our 600 mile trip. The prior owner kept the fluids changed as required, we have the Carfax. Tranny fluid was flushed at 121,000 miles, now has 163,000. Should I have it flushed again at 40,000 miles?

As a long time RV'er, I know that the tranny is the weak point in any towing drive train, just haven't had any experience with the 4L60 so am looking for guidance. Used to tow with 1965 Chevy Van, 292-TH350 and an '88 Burb with 454..

 

[Supercharged111]

4L60 is absolutely the weak point. Is a 4L80 swap something you'd pursue? I'd venture to say it's just a matter of time before the trans pukes. Towing in OD is hard on the 3-4 clutch pack. I towed open deck in OD as my truck allowed back then, but every day since the 4L80 went in has been nothing but peace of mind. That and the shallower OD means it pulls better in 4th gear. I don't know anything about a Fastchip, but the tune is absolutely critical for pulling power. The computer needs to know that it has a 383 instead of a 350 now at the absolute least.

 

[skylark]

383+4L60E=

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[df2x4]

Agreed with the others, I'd look into a 4L80E swap. You'll need to get the PCM tuned for the new engine to maximize potential as Supercharged mentioned but you'll also need to tune it to control an 80E instead of a 60E, so you could kill two birds with one stone there. I'd recommend Black Bear Performance for the tune if you want to go mail order, they tuned my red truck and have been awesome to work with. Including when I 4L80E swapped that truck.

EDIT - Just realized you said the truck was a '94, Black Bear can only tune '96 and up PCMs. I'm sure someone over at the Gearhead EFI forums can help you though.

 

[jrsroadhauze]

3 years ago Bought our '94 GMC k1500 to tow our 28' TrailCruiser that only weighs 5,000 lbs loaded. Was a one owner, always garaged crème puff, however 350 sucked, still had original plugs, wires, cap & rotor at 126,000 miles. Would barely go 65 mph and wouldn't tow till I removed original air cleaner setup and ran two 4" cold air intakes, MSD adjustable timing control, Fastchip and dual exhausts. Still wasn't acceptable so just had a new 383 stroker installed. Can't believe the torque. Found that the new engine didn't like running a high rpms in 3rd while towing, so put in 4th and it just settled in and ran easy, didn't hunt or have to shift down or unlock torque converter until going up steep hills. (Burb is an SLE with complete tow package, trans & oil coolers etc.)

So, the question is, is that going to hurt the 4L60e? Shifts good and didn't get hot on our 600 mile trip. The prior owner kept the fluids changed as required, we have the Carfax. Tranny fluid was flushed at 121,000 miles, now has 163,000. Should I have it flushed again at 40,000 miles?

As a long time RV'er, I know that the tranny is the weak point in any towing drive train, just haven't had any experience with the 4L60 so am looking for guidance. Used to tow with 1965 Chevy Van, 292-TH350 and an '88 Burb with 454..

Did you keep the TBI on the 383?

 

[PlayingWithTBI]

I'm sure someone over at the Gearhead EFI forums can help you though.

^^^What he said, Dave W (Old School EFI) on gearhead-efi.com can help you there.

 

[Tim W]

I just went through this. My bone stock 4l60E lasted 600 miles with my 383. Now i have a built transmission.

 

[L31MaxExpress]

Stock 4L80E out of the mud is stronger than the Level Infinity built 4L60E.

With a TBI it is a matter of adding input speed signal wires, moving a couple of wires in the big round connector and swapping the chip to one for a 4L80E truck.

My stock L31 350 killed the stock 4L60E at 38K and a built 4L65E in 40K. Threw a stock 4L85E with a Transgo HD2 kit in its place.

 

[LVJJJ]

Kinda what I was afraid of. However, I'll keep using the 4L60 till it pukes. I do want to add a trans temp gage, I see where one of the gage companies (Glow Gauge) has special sending unit that screws into a test port somewhere on the tranny? Where is it and would that work, instead of drilling a whole in the pan???

Yes I kept the TBI. Got rid of the Fastchip the maker said it would make the 383 run too lean. Was for WOT power.

 

[PlayingWithTBI]

I see where one of the gage companies (Glow Gauge) has special sending unit that screws into a test port somewhere on the tranny?

The test port is on the driver's side towards the upper front (1/8" pipe thread). The problem with that port is you get accurate pressure readings but, because it's not in the flow stream of the fluid, it is way too slow responding to temps. You should weld/braze in a port in the pan (which you can use for draining), so you're seeing actual fluid temps.