Originally Posted by
XtremeRevolution
Alright, so I have a very, very strange problem that perhaps some of you can help me with.
1995 Regal, L67 engine swap, 3.4 pulley, headers, CAI.
1999 Monte Carlo PCM
2003 Buick Century 4T65E + HD trans, 3.29FDR, 86k miles
A friend of mine finished the swap for me recently, and due to problems tuning (partially due to rotten vacuum hoses and also due to insufficient fueling), he left me with his HPTuners interface so we can get the tune working.
The transmission doesn't catch 1st gear. Its that simple. Plus, it occasionally slips at WOT at higher RPMs in 2nd and 3rd. When colder, it will stutter while accelerating from a stop in 1st gear or simply not catch on until a higher RPM, but after you abuse it for a while, the slipping becomes worse.
I went to a transmission shop and they pulled a code: P0748 - pressure control solenoid electrical. They tried to convince me that the sprag assembly is broken and that's why it doesn't engage first gear. The clutch pack isn't bad because if it was, the clutches would be burning against each other and my fluid would smell. It does not smell.
If I manually downshift into 1st gear when slowing down and coming to a stop, at exactly 10mph (as is in the tune), every single time, the car will give a a light jolt engagement into 1st gear, and when I accelerate from that stop, I have perfect gear engagement and can roast my tires all day long. If I know I'm going to come to a complete stop, and I downshift into 1st gear after I've already stopped, I will have 1st gear when I accelerate again. If I do not downshift into 1st, I have no first gear, and upon acceleration the car barely moves.
I've already tested the PCS. Resistance is 5.3ohms, and there is no wiring fault between the 20-pin trans connector to the PCM on the PCS high and low wires. This transmission was bought with a 6 month warranty from a company that parts out auto insurance auction cars. This particular transmission had 86k miles and the salesperson said that this transmission was road tested before being pulled.
I have heard that the PCS is different between the years 2002, 2003, and 2004, and that the 2003 transmission has an electrically different PCS. As a temporary solution, we've disabled the P0748 code to prevent the car from going into limp mode, as it is perfectly driveable so long as it doesn't do that. I'm wondering if the 99 Monte Carlo PCM doesn't know what to do with this transmission.
My guess right now is that there isn't enough line pressure to engage the clutches, and I'm considering altering the Force Motor Current tables in order to increase line pressure. I don't know how this PCS differs from the 98-02 versions.
Any light anyone can shed on this issue would be very much appreciated. I'd like a more intelligent answer than just "you need a rebuild now" because as I mentioned, if I manually shift the gears (using the shifter linkage), everything works like a charm, and the car goes like a bat out of hell, which leads me to believe that the problem is not mechanical.
Thank you in advance.