1998 C1500 - Firming up trans shifts a bit - HPTuners

So I went in with a buddy on HPtuners and figured I'd play with it on my truck a bit. I used the credit and unlocked it to my vin then realized everybody hates the "blackbox PCM" that it has in it.

All I'm trying to do right now is firm the transmission shifts up a bit, but coming from the older stuff not sure where to begin. And I'm not talking neck snapping shift kit shifts, just a little better than stock.

I'm really having a hard time finding much info for this truck with it's redhead stepson of a blackbox PCM.

Auto shift properties > Shift Time
I planned on just cutting the stock times in half.

Auto shift properties > Shift Pressure
Should I just bump up the max pressure a few (stock is 90) and scale up the Shift Pressure Upshift tables a bit?
Some people seem to rather leave the pressures alone and just remove a little bit of torque management in the trans. It's a tired 4l60e, so I don't want to kill it. Just make the truck a little more fun to drive.

I have been looking into doing the same thing, only on the ODB1 platform - the concepts are the same though. I found this thread that covers a lot of good info, and its specifically for HPTuners to boot: http://www.ls1gto.com/forums/showthread.php?t=356667

For me, I found zero'ing out the shift times, and increasing line pressure around 15% helped. I also had to increase line pressure in the lower ranges due to the high stall converter I'm running. You may also want to look into setting Min/Max TCC duty cycle to 90/100 as suggested in that link. Good luck! :-)

Quote:

---

Originally Posted by dubwise

I have been looking into doing the same thing, only on the ODB1 platform - the concepts are the same though. I found this thread that covers a lot of good info, and its specifically for HPTuners to boot: http://www.ls1gto.com/forums/showthread.php?t=356667

For me, I found zero'ing out the shift times, and increasing line pressure around 15% helped. I also had to increase line pressure in the lower ranges due to the high stall converter I'm running. You may also want to look into setting Min/Max TCC duty cycle to 90/100 as suggested in that link. Good luck! :-)

---

I wouldn't zero out the shift times. It's hard on the transmission internals. If you leave a little time for the components to slow down before you completely stop one moving part, you will decrease the chance of snapping a reaction shell and losing 2,4 and Rev. I would recommend installing the corvette servo with the Gil Younger shfit kit springs and mods in the servo. This will clean up the 1-2 and 2-3 shifts. double duty firming up the 1-2, 2-3 shifts and extending the life of 3-4 clutch. Bumping the pressure is a good idea, but only to the fact that as transmissions age they develop internal leaks(and external leaks too :) ) which result in pressure loss at various valves and the clutch/band/lube circuits. Remember as you raise the pressure in the trans you are also increasing drag on the engine, minimal but still. :) Also, just in case you like to stomp on it from a stoplight, pull the gearshift into at least manual 3. This engages the coast clutch giving addition clutch capacity.

Buddrow

Quote:

---

Originally Posted by buddrow

I wouldn't zero out the shift times. It's hard on the transmission internals. If you leave a little time for the components to slow down before you completely stop one moving part, you will decrease the chance of snapping a reaction shell and losing 2,4 and Rev. I would recommend installing the corvette servo with the Gil Younger shfit kit springs and mods in the servo. This will clean up the 1-2 and 2-3 shifts. double duty firming up the 1-2, 2-3 shifts and extending the life of 3-4 clutch. Bumping the pressure is a good idea, but only to the fact that as transmissions age they develop internal leaks(and external leaks too :) ) which result in pressure loss at various valves and the clutch/band/lube circuits. Remember as you raise the pressure in the trans you are also increasing drag on the engine, minimal but still. :) Also, just in case you like to stomp on it from a stoplight, pull the gearshift into at least manual 3. This engages the coast clutch giving addition clutch capacity.

Buddrow

---

Good info, thanks. May be a good call on the shift times. I recently changed mine and so far so good. My stock shift times were as high as 400ms and as low as 225ms. If I was to cut them in half, I'm not sure I would be able to tell the difference between, say 400ms and 200ms shift time. Any advice on the shift times, numbers-wise? I have not found much guidance on that around the web. When I datalogged I was getting as low as .050 shift times. Maybe 100ms or .075...?

I'm running a 4L80E with a 700HP carbed 540ci, so if the trans breaks I won't be all that suspicious of the line pressure or shift times (at first anyway). :-D

Good information there.

I've always read use the stock shift times, cut in half as a baseline.

The corvette servo is also the #1 thing everyone recommends doing to improve the 4l60's. For the price, I just need to order it and try it. Just hoping my exhaust isn't in the way.

What would you say is a "safe" max pressure for a older trans? Stock is 90, I was thinking no more than 10%

Some guys ZERO out the shift times to disable the Adaptive Shifting algorithm when shift kits are used.

Corvette servos work well, my 97 reg cab shortbox went from ok WOT 1-2 upshifts to barking the tires during WOT upshifts. Part throttle shifting was only moderatley firm, just like they should be.

peace
Hog

Quote:

---

Originally Posted by Hog

Some guys ZERO out the shift times to disable the Adaptive Shifting algorithm when shift kits are used.

Corvette servos work well, my 97 reg cab shortbox went from ok WOT 1-2 upshifts to barking the tires during WOT upshifts. Part throttle shifting was only moderatley firm, just like they should be.

---

Does your truck have that goofy dual to the muffler exhaust? If so were you able to do the servo without dropping the trans or disconnecting the exhaust? The exhaust being in the way is the only reason I havn't done it on mine yet.

If you don't reduce the stock shift times the PCM will reduce the pressure to make them match with the table, you may end with a burnt transmission.
You don't always need to make them zero, change them to a realistic value and test if it shifts the way you want.

The more power you have, the faster the shifts need to be to avoid slip (wear). Some combos need shift time set to zero and also to up the trans pressure. Other combos are ok with a 20% faster shifts.

Quote:

---

Originally Posted by scoob8000

Does your truck have that goofy dual to the muffler exhaust? If so were you able to do the servo without dropping the trans or disconnecting the exhaust? The exhaust being in the way is the only reason I havn't done it on mine yet.

---

My truck wis a 1997 with the Vortec 350 L31 stock, as such is had the dual cat into single muffler stock. The L35 4.3 V6 and the L30 Vortec 305 both have the y-pipe into a single cat and have 3 precat O2 sensors and a single aftercat O2 sensor. The L31 Vortec 350 and Vortec L29/Vortec L21 454 have dual cats with 2 precat O2 sensors and 2 aftercat O2 sensors.

In this picture the 1/2 ton dual cat Vortec 350 exhaust is pictured with dual 1 7/8" piping. The dual cat exhaust of teh right is teh stock dual cat exhaust from a Vortec 350 equipped truck that was a 3/4 ton. The 3/4 tons got the dual 3" headpipes and larger cat setups.
http://i1202.photobucket.com/albums/...xhaustback.jpg

ANd here 3/4 ton L31 headpipe/cat assembly on the left, and the 1/2 ton Vortec 350 assembly from a 1/2 ton truck.
http://i1202.photobucket.com/albums/...haustfront.jpg

It was so long ago that I cant remember if I had the stock 1/2 tone headpipe/cat assembly or if I had my long tube headers/dual 2-1/2" into dual in/dual outlet into dual 4" sidepipes that exit before teh passengert side rear tire.

I do remember that it was tight, but I was able to do so without much difficulty. I removed teh servo cover and installed the Vette servo without dropping the trans of the exhaust.


peace
Hog

Quote:

---

Originally Posted by Hog

My truck wis a 1997 with the Vortec 350 L31 stock, as such is had the dual cat into single muffler stock. The L35 4.3 V6 and the L30 Vortec 305 both have the y-pipe into a single cat and have 3 precat O2 sensors and a single aftercat O2 sensor. The L31 Vortec 350 and Vortec L29/Vortec L21 454 have dual cats with 2 precat O2 sensors and 2 aftercat O2 sensors.

In this picture the 1/2 ton dual cat Vortec 350 exhaust is pictured with dual 1 7/8" piping. The dual cat exhaust of teh right is teh stock dual cat exhaust from a Vortec 350 equipped truck that was a 3/4 ton. The 3/4 tons got the dual 3" headpipes and larger cat setups.
http://i1202.photobucket.com/albums/...xhaustback.jpg

ANd here 3/4 ton L31 headpipe/cat assembly on the left, and the 1/2 ton Vortec 350 assembly from a 1/2 ton truck.
http://i1202.photobucket.com/albums/...haustfront.jpg

It was so long ago that I cant remember if I had the stock 1/2 tone headpipe/cat assembly or if I had my long tube headers/dual 2-1/2" into dual in/dual outlet into dual 4" sidepipes that exit before teh passengert side rear tire.

I do remember that it was tight, but I was able to do so without much difficulty. I removed teh servo cover and installed the Vette servo without dropping the trans of the exhaust.


peace
Hog

---

It amazes me to this day how tiny those pipes are and how much the remind me of the stock 2 1/8" od setup on my Titans. Probably why my stock Express ran as well as it did....2.75" pipes on my G1500.

http://i243.photobucket.com/albums/f...ps94354112.jpg

I'm running that 3/4 ton exhaust on my truck minus cats, except I used an '02 3/4 6.0L muffler and tailpipe, salvage yard special lol. The 3-1/2'' single tail pipe looks good on the old '89.