My line pressure is 90. (by PCM/HPT)
I was wondering if turning it up a little would be safe/helpful
to the life of the tranny? (by PCM/HPT)
Is it good to run a corvette/billet servo/TransGo in
conjunction with upping the line pressure through the
computer? (manually and by PCM/HPT)
I know you can manually, open the tranny, and
turn the knob to turn up the line pressure, but didnt know
if doing both would be safe? like you'd have 2x the pressure!
Last edited by slow6; 12-16-2005 at 03:03 AM.
This is a lot like my question...
Is this a good idea using HPT without a built tranny or aftermarket shift kit installed? I used to have the B&M Shift IMprover which to my knowledge just boosted line pressures in the tranny, and i heard this was actually bad for teh life of the transmission and stopped using it.
Isn't tuning this in HPT the same thing?
Anyone??
1997 Camaro RS
T3 Turbo intercooled.
I've been messin' around with shift pressures and such for a little while now. I'm sure it decreases the life of the tranny, but for now, I'm shifting great. GrandAms have a tendency to 'granny shift' so I increased shift pressures for each shift.
I left the max line pressure above at 90 and left the force motor current alone too. The max line pressure value just tells the pcm which column in the force motor current to max at. Before getting shift pressures added to HPT, I had decreased the values in the force motor current table by about 5 or 10 and it helped my shifts.
Well, here's my experience from working as a GM dealer service manager. As trans hard parts wear, the shift time in the pcm remains the same. If the clutches start to slip, the pcm raises line pressure to keep the shift times where programmed. Eventually the pcm can't make up for the slip and then all of a sudden customer states "my tranny is slipping". It's too late at that point.
I believe that the less time the tranny has to "slip" between gears, the longer the clutches will last.
2000 GTP- S2X, diamond forged 9.5:1, balanced, Lucas 42.5#, GenV w/N*, stage 3 heads, custom PCM, ZZP SS IC, TOGS, MPS 3.0, Intensified 3.69's tranny - low 12's!!!!
I changed all the values in my desired shift time tables to .275. This makes your shifts quicker. Don't go below .275 though, I have read that people have lost trannies going lower than that. .275 is the safest until you start threatening your trans.
I heard bumping the line pressure isn't a good idea, so I did the shift time changes and helped my shifts quite a bit. Feels like I have a shift kit in the car now just by tweeking the settings a little.
What do you think you're doing when you change the shift times?? Requesting the pcm to shift faster is asking for more line pressure. That's how the pcm makes the shift times happen.Originally Posted by 97rs4life
2000 GTP- S2X, diamond forged 9.5:1, balanced, Lucas 42.5#, GenV w/N*, stage 3 heads, custom PCM, ZZP SS IC, TOGS, MPS 3.0, Intensified 3.69's tranny - low 12's!!!!
Is the 'performance' section for this WOT shifting? I wouldn't mind have those numbers quicker but i like the factory shifts for daily driving.
1997 Camaro RS
T3 Turbo intercooled.
Nevermind, i see where it differentiates WOT shiftingSometimes i'm not the brightest bulb
1997 Camaro RS
T3 Turbo intercooled.
My girlfriends 04 GT grand prix is non responsive to any stimuli. I have tried lowering shift time. I have tried changing motor force, and line pressure. No matter what I have moved on the HPT, nothing has made this stupid car shift any harder. I think it hates me.
Have you taken Torque Management out? That made it lag for me before shifts, and basically make noise.
OO GTP, with the electronic trannies, the PCM doesn't increase line pressure to quicken the shifts. Solenoids are used to engage the clutches and bands, during a shift, one solenoid releases and another one engages.
Shortening shift time just decreases the interval between the first one disengaging and the second engaging.
As a quick tutorial for those of you new to these trannies, I'll spill a bit of my experience (one full rebuild, one partial rebuild to replace a broken input drum, and a parts swap to repair a broken band in a 4L60E).
Lots of line pressure is bad, very bad. The more you increase line pressure, the harder you slam parts together.
The PROPER way to do it requires a few parts and some reprogramming:
1 - Use larger apply pistons, they provide more holding force, but the piston isn't slammed into place by higher line pressure.
2 - shift fixer kits, a couple of companies sell them, and they fix a number of known problems with the tranny, and also allow you to adjust fluid flow to certain parts to make them apply quicker, firmer, etc.
3 - DO NOT go using super-stiff accumulator springs, they are there to absorb shock at apply; stiffening them excessively will cause broken parts.
4 - Adjust the tranny shifting tables...I used the '04 GTO tables for time and pressure, and they work great.
5 - Definitely get an aftermarket torque converter. It doesn't have a to be a super-high stall one (I have a 2800 stall), but it will make light-years of difference in the way that it feels.
6 - IF YOU DO THE THINGS I HAVE LISTED ABOVE, THEN DO THIS TOO -
Do not use the Dexron Transmission Fluid, it slips too much, and if you have shortened your shifts, you run the risk of having clutches and bands slip when shifting at high rpm. It has happened to me. I now use Red Line Racing ATF, it is basically a Ford Type F fluid, but I can't say for certain that non-synthetic Type F is the same (i.e., I if you go the cheap route, and buy the cheap fluid, I can't guarantee that it will behave like the Redline).
Dexron is designed to allow the clutches to slip when engaging, that's what makes for the nice, soft granny shifts. The Racing ATF is designed to not be slippery, it actually has gritty stuff in it, and when the clutches lock up, they lock-up, like right now.
DO NOT put Type F in a stock tranny, I haven't tried it, but I'm pretty sure it will tear up the friction materiels (clutches and band) because of the slow shift times. By the way, the Redline Racinf ATF provides all of the same lubrication, etc., that the Dexron does, I spoke with the engineer at Redline and confirmed that. I have been using it since my last time with the tranny out, in the fall of 2004, and it has been running like a champ.
Lastly, don't let a tranny shop guy talk you into a whole bunch of really cool parts that will make your tranny shift so hard "that you'll spin the tires going into 4th on the freeway".
The main things that you will need for any rebuild, as long as the tranny hasn't grenaded, are clutches, the metals that go between the clutches, a band, replace the seals, wash the case, inspect all the hard parts, and a new or rebuilt torque converter.
Hope this helps, John
I will agree to a certain extent. Yes shift solenoids such as the 1-2, 2-3 are used for the shift, but line pressure is what makes the shift happen in a shorter/longer period of time. That is one of the reasons we have to do a trans adapt pressure learn when installing a new tranny after a failure. When the clutches/discs start wearing, the pcm raises line pressure to accomodate for the longer than desired shift times and on the new tranny, you don't want that kind of "commanded" line pressure.
I agree ENTIRELY with the remainder of your post. Redline is the BOMB, and the less time the clutches have to "slip" the longer they will last.
2000 GTP- S2X, diamond forged 9.5:1, balanced, Lucas 42.5#, GenV w/N*, stage 3 heads, custom PCM, ZZP SS IC, TOGS, MPS 3.0, Intensified 3.69's tranny - low 12's!!!!
ok, dont put Redline Type F in a stock tranny because of the slow shift times.
Well, what if you have a stock tranny with programmed faster shift times?
00GTP, the shift timing is actually set using the solenoids. The PCM will use the line pressure to make the pistons move faster, to make up for larger apply distances as a result of wear, but it's going to be relatively small changes, compared what people are doing with shift kits, etc.
Boosting the line pressure like the shift kits do is just a band-aid, and that's what I want people here to understand. People get the impression, I had it before too, that jacking the line pressure up is the only way to quicken shifts. They need to know how to do it properly, now that we have the ability, and get a tranny that both shifts better, and doesn't destroy itself.
My tranny had the torque converter clutch slippage problem, and the PCM's band-aid for that was to max the line pressure. It made for some wicked shifting on the freeway, but that, along with the overheating caused by the slipping TCC, also resulted in ripping out the teeth in the back of the input drum that hold the 3/4 clutches in.
Slow 6, take a whack at it, if you have reprogrammed the shift times yourself, then you SHOULD be alright. However, I don't know how well stock, used frictions will react to the Type F fluid, in terms of how well they will stand up to it.
They may be fine, but, as I said, the Type F actually has a gritty material in the fluid, to help make the fluid less slippery. That material may actually chew up the stock frictions in your tranny faster, due to the fact that your frictions are "old".
My tranny is now basically a 4L65E in terms of hard parts, all aftermarket for frictions, I have different accumulators springs and pistons, and I completely re-did my shift pressures as well. I was dealing with a basically new transmission, as well as the non-stock parts, when I started using the fluid.
Also, don't shorten your shifts up too much, you can actually cause them to bind, i.e., both gears are momentarily engaged at the same time.
Also, one other thing, if you drag race, and decide to use the Redline Racing ATF, it is heavier, and will change your converter stall speed.
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