ive been looking into this for a while now...but i just wanted some clear numbers.....is it true that line pressure builds from idle to 1800rpm and then dont increase anymore?? or what are the rpms? cause im starting to feel guilty about crusing around town at 1600rpm locked....what about if u dont tow? and have stock power? will driving at 1400rpm hurt my truck?.....i visited DTT as well and i understood that its extremely hard to overpower the lockup system once at max line pressure and that failures occur due to leakage not overpowering the lockup clutch

another issue i wanted clearup on...what is line pressure dependent on??? is it throttle or rpms??? because if its throttle and i get a 4k gsk then im using less throttle to rev to 2000 and then my line pressure would be lower than what they used to and id be hurting my tranny no?...but if its controlled by rpms then we should all get a 4k gsk kit and actually benefit the tranny

what about increasing the line pressure on my 95?? how much?

please feel free to educate me as much as possible ...i need lots of info

 

Here are some of the answers.
Line pressure is mostly dependent on the throttle position.

The 4 k gsk won't have anything to do to it. It only allows the Cummins to rev farther.

You can most likey raise the line to 70 psi without it causing seals to go, but it is a risk.
Those that have GSK say it is the best thing done to it.
It won't de-fuel at 2500 rpm.

 

Here are my latest pressure test results.......granted for an aftermarket trans with higher pressures, but it tells you a trend between TV opening and throttle position. Note some of the tests are at idle, and the TV valve controlled by hand. You can see the rise in pressure. Then another test at 1600, study the pressures, for the trend will be the same for yours albeit lower......



Pressure Test Results

Stall Test: Idle 75 psi, WOT 120 psi

Test #1:
Accumulator port @ 1000 rpm manual first gear
no TV opening 75 psi
full TV opening 120 psi
Rear servo port @1000 rpm "L"ow range
no TV opening 75 psi
full TV opening 120 psi

Test #2:
Accumulator port @ 1000 rpm manual 2nd gear
no TV opening 75 psi
full TV opening 120psi

Test #3:
Accumulator port @1600 rpm "D"rive gear OD locked out
no TV opening 85 psi
TV opening at downshift threshold 130 psi
full TV opening 140 psi
Front servo port @ 1600 rpm "D"rive gear OD locked out
no TV opening 85 psi
TV opening at downshift threshold 140 psi

Test #4:
Rear servo port @ 1600 rpm "R"everse gear
no TV opening 215 psi
half TV opening 315 psi
full TV opening 365 psi

Test #5:
Governor test port "D"rive OD locked out variable speeds
25 mph 40 psi
30 mph 55 psi
35 mph 65 psi
40 mph 75 psi
50 mph 80 psi
55 mph 80 psi

Hope it helps

Chris

 

thanx guys im studying im studying ....whats with the reverse gear? thats alot of pressure ....am i reading wrong or is the dif in psi between 1000rpm and 1600rpm very small....so its dependent on throttle huh....so babying it is the worst thing u can pretty much do huh

 

Just baby it til it gets to operating temp and let the Cummins drink.

 

So now lets put that into the real world. You have a 12v with injectors and pump work. Power available at 10% throttle is much more than before. 5% throttle moves you out pretty good (rpm wise) and before you know it, the converter locks with low line pressure, low throttle position, and more power. The lockup clutch won't take that for long. Then folks that were crusing along at 45 mph then romping on it with all that power was stress too. So first came higher pressures, and lower stall converters, then came billet covers with more surface area, then billet 3 disk.

 

does the line pressure reach its peak?? is it 1800rpm?

does this low line pressure affect my gears when i not locked up? say im just going at 1200rpm in a plaza in 2nd gear...should i try and avoid that?

 

Pressure is boosted in reverse, because in reverse, often you are asking a lot of the truck, (moving loads, trailers, etc.) and the gearing is often not low enough. I am surprised the pressures were not boosted in manual low. I was taught that they were.

 

so the tranny has a better chance/is happier if i generally have my foot in her?

 

To a point. Also depends on when you decide to plant the go pedal.

Planting it off the line and holding it is a bit easier on it (w/ stock tranny), to get up to speed. If you ease into the throttle 'til you lock-up in O/D (especially during lock-up), then mash it, you run the risk of slipping the lock-up clutch. Even on a stock engine. I could pretty easy. Not to mention after the fuel mods.

New tranny is great! Can't slip this one.

 

im really looking into getting the 4k gsk this summer .....when i give her gas and get it up to 2600rpm it shifts so hard!!! with lots of rpm drop....i can only imagine what the shifts are with a 4kgsk at 3500rpm....i know everyone says its so much more driveable with the gsk's but i thought maybe it would totally take the low line pressure problem out of the equation since ur spending alot of time driving over 2000rpm.....am i somewhat accurate? or will the line pressure issue not change whatsoever if i get the gsks.....it would be nice to take advantage of the TC stall with the gsks and have a firm lockup at high rpms

know what i mean?

Andrew

 

Line pressure is primarily dependant on throttle position, not engine RPM...

From what I understand, the GSKs generally benefit folks because it allows more power to be made at higher RPM, which is closer to the stall speed of the stock torque converter.

 

The good folks at BD have a handy gadget to increase lockup pressures by rotating the throttle pressure lever after lockup. Go to www.bd-power.com and click on Ram Diesel. It's called the PressureLoc. Won't take the place of a performance transmission, but it's ideal to use with mildly bombed engines.

 

The GSK's are also a benefit because of the too weak throttle vlave spring in the valve body. Under full TV opening (which occurs at full throttle), the shift pattern is set to occur AFTER the engine runs up against the governor. The GSK's open up the rpm potential of the engine, thus allowing the shift, rather than hanging gears due to lack of engine rpm. A heavier TV spring will allow a shorter shift pattern, but also effects downshifting when decelerating....it's a trade-off. A gsk covers it nicely without sacrificing drivability.