4L80e No engine braking

[tayto]

can you find out what shift kit? the HD2 kit use to have you put a spacer on the 2-1 servo, but removed it in later revisions.

 

[WannaBe1Ton]

can you find out what shift kit? the HD2 kit use to have you put a spacer on the 2-1 servo, but removed it in later revisions.

I’ll double check but believe it was a trans go kit.

 

[L31MaxExpress]

I engine brake frequently with a load or even on some roads I drive regularly. There are some very steep grades on some of them and I would rather downshift and make sure I can maintain control, rather than hoping the brakes work. I also downshift coming off downhill off ramps, easier to already be slowing down and increase braking with the brakes if needed. Mine will downshift to 2nd at 70 mph and 1st under 40 mph. I just give it a little throttle as I move the shifter to help cushion the engagement.

 

[WannaBe1Ton]

I engine brake frequently with a load or even on some roads I drive regularly. There are some very steep grades on some of them and I would rather downshift and make sure I can maintain control, rather than hoping the brakes work. I also downshift coming off downhill off ramps, easier to already be slowing down and increase braking with the brakes if needed. Mine will downshift to 2nd at 70 mph and 1st under 40 mph. I just give it a little throttle as I move the shifter to help cushion the engagement.

haha glad someone else knows how to drive a truck. I just wish i had 2nd lol. Guess im gonna have to tear it down and check that servo

 

[L31MaxExpress]

haha glad someone else knows how to drive a truck. I just wish i had 2nd lol. Guess im gonna have to tear it down and check that servo

Well I was at about 14-15K combined a couple of days ago and the van itself is nearly 7K. I built the 383 to work it. There is a reason it has a 4L85E and 10.5" 14-bolt in it.

 

[pressureangle]

While the transmission schemes in the PCM vary from year to year and vehicle types, the fundamental issue here is the torque converter. My 5.7 4l80e has significantly more decel than my 6.5 diesel 4l80. The diesel converter flashes to about 2400rpm, the gas motor only about 1900; also the gas truck is 4.10 while the diesel is 3.74 so the gas trans spins faster at a given speed. The converter unlocked has very little drag, which is part of the 'fleet mileage' necessity of EPA and DOT tax relief (and cost of ownership which is huge to OEMs) Some transmissions, I think including the 4l80 have built-in braking which keeps the converter clutch locked in certain environments- like idle throttle and manual commanded 3rd gear. Later trucks have 'tow mode' of course, which primarily provides firmer shifts at higher rpm for heat reduction, and downshift/TC clutch engagement for engine braking. It's hard to know without some OEM internal knowledge. I do know I can change a lot of this stuff in the 4l80 through TunerPro.

 

[L31MaxExpress]

While the transmission schemes in the PCM vary from year to year and vehicle types, the fundamental issue here is the torque converter. My 5.7 4l80e has significantly more decel than my 6.5 diesel 4l80. The diesel converter flashes to about 2400rpm, the gas motor only about 1900; also the gas truck is 4.10 while the diesel is 3.74 so the gas trans spins faster at a given speed. The converter unlocked has very little drag, which is part of the 'fleet mileage' necessity of EPA and DOT tax relief (and cost of ownership which is huge to OEMs) Some transmissions, I think including the 4l80 have built-in braking which keeps the converter clutch locked in certain environments- like idle throttle and manual commanded 3rd gear. Later trucks have 'tow mode' of course, which primarily provides firmer shifts at higher rpm for heat reduction, and downshift/TC clutch engagement for engine braking. It's hard to know without some OEM internal knowledge. I do know I can change a lot of this stuff in the 4l80 through TunerPro.

My stock 5.7L flashed the stock gas converter 2,500 rpm in my van.

 

[pressureangle]

My stock 5.7L flashed the stock gas converter 2,500 rpm in my van.

That's my point, I don't know that there's any way to verify that any particular vehicles use the same converter. The same converter will flash differently behind different motors; more torque = higher flash. My 5.7 is a '94 K2500 with 8600lb gvw. It's a fleet order for towing. <shrug> if somebody has OEM data I'd review it.

 

[Supercharged111]

That's my point, I don't know that there's any way to verify that any particular vehicles use the same converter. The same converter will flash differently behind different motors; more torque = higher flash. My 5.7 is a '94 K2500 with 8600lb gvw. It's a fleet order for towing. <shrug> if somebody has OEM data I'd review it.

Big blocks and diesels supposedly got a tighter converter than the 350, 1600 RPM IIRC vs 2000+. Maybe your motor is weak and just not flashing the converter all that high?

 

[pressureangle]

Big blocks and diesels supposedly got a tighter converter than the 350, 1600 RPM IIRC vs 2000+. Maybe your motor is weak and just not flashing the converter all that high?

With the 400sbc it flashes about 2200. The point here is, you can't know if the converter is the same without direct knowledge. But the OP is about coasting, which is built in to the trans/converter and shift scheme.