Road race guys, Transmission questions

[rat]

There is an scca road course thing in one of the parking lots in a couple weeks. And i was thinking of trying it. Speeds are suposed to be under 60mph. I don't plan on doing this very often(probably just this one time), and don't plan on compleatly revamping my truck just for this use.


Now, my question, should i alter my shift points for this? I have an automatic. And i was thinking it might not be a bad idea to have it hold gears for longer so that when i come out of a corner it isn't down shifting and upseting my chassis. It sounds like it is going to be a lot of 1st and second gear running, i can run 2nd gear all the way up to 70mph i think.


I can change my shift points to whatever i want, so let's hear some opinions.

The truck:
4.3 Automatic 3.42 Rear end
Mild cam
Zq8 Suspention

[Sparky2263]

If you're road racing, your gonna want to be shifting manually. Corner entry from high speed will dictate downshifting to take advantage of engine braking. Otherwise, you're gonna have brake fade real quick.

[rat]

Hm, that sounds scary. Due to the fact that if i go to far and pop it into the wrong gear(reverse is what i am worried about). Plus with the column shifter this isn't an ideal situation.

I was thinking i can program the second gear position to stay in first gear no matter what the throttle angle to stay in first til say 25mph(even at 0% throttle). Then i will get the engine braking bennifits, and coming out of the corner in the correct gear.

[Sparky2263]

If it downshifts on corner exit, you're screwed (and looking back at where you just came from).

I got an idea. Take a look at the description of manual second (below). The only difference is noted, that the PCM will not allow manual 1st because it won't energize the 1-2 shift solenoid. You take the O/D lamp output, wire it to the 1-2 solenoid and VOILA! pushbutton shifting between 1st and second only via the O/D off switch (shifter will stay in manual 2nd range).

Whatcha' think?




Manual Second Gear

A manual 3-2 downshift can be accomplished by moving the gear (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860212/56231659) selector lever into the Manual Second (2) position when the transmission is operating in third gear. This causes the transmission to shift immediately into second gear regardless of vehicle operating conditions. Also, the transmission is prevented from operating in any other gear, first, third or fourth. The following information explains the additional changes during a manual 3-2 downshift, as compared to a forced 3-2 downshift. Some vehicles in manual second gear will start out in first gear, while other vehicles will have a second gear start. Refer to the owners manual for specific applications.

Manual Valve
The selector lever moves the manual shaft and the manual valve into the manual second (2) position. This allows the line pressure to enter the D2 fluid circuit.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly
The D2 fluid is routed to the TFP manual valve position switch where it opens the normally closed D2 fluid pressure switch. With the D2 and the D3 pressure switches closed and the D4 pressure switch open, the TFP manual valve position switch signals the PCM that the transmission is operating in manual second.

Third and Fourth Gears Prevented

2-3 Shift Solenoid (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/96356796/56220167) (SS) Valve
The PCM energizes the 2-3 SS valve and the AFL fluid pressure holds the 2-3 shift valve in the downshift position. This electronically prevents operation of the third and fourth gears.

2-3 Shift Valve Train
The D2 fluid is routed between the 2-3 shuttle and the 2-3 shift valves and causes the following:


Regardless of the operating conditions, the D2 fluid pressure holds the 2-3 shift valve in the downshift position against the AFL fluid pressure.
The 2nd fluid is blocked from entering the 3-4 signal fluid circuit and the 3-4 signal fluid circuit is open to an exhaust port at the valve.
The 3-4 clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56222273) cannot apply with the 3-4 signal fluid exhausted. Therefore, third and fourth gears are hydraulically prevented.
The 2nd fluid feeds the servo feed fluid circuit, but the 2nd fluid circuit has no function in manual second.
The AFL fluid is blocked by the 2-3 shift valve and the D432 fluid circuit is exhausted through the valve.
The overrun fluid is exhausted through the 2-3 shuttle valve.
1-2 Shift Valve
The 1-2 SS valve is OFF, the signal A fluid exhausts through the solenoid and the spring force holds the valve in the upshifted position.

First Gear (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860212/56231659) Prevented
The prevention of first gear is controlled electronically by the PCM through the 1-2 SS valve. The PCM keeps the 1-2 SS valve de-energized, regardless of the vehicle operating conditions when the TFP manual valve position switch signals manual second gear range. This keeps signal A fluid exhausted and the spring force holds the 1-2 shift valve in the upshift position.

Overrun Clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56222273) Remains Applied

Overrun Clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56222273) Feed Checkball (#5)
Orificed D2 fluid pressure seats the #5 checkball against the empty overrun clutch fluid (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860772/97115202) circuit. This is done simultaneously with the overrun clutch fluid exhausting so that there is a continuous fluid supply to the overrun clutch feed fluid circuit.

Overrun Clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56222273) Piston
A continuous supply of fluid pressure is routed to the piston in order to keep the overrun clutch plates applied.

Torque Converter Clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56227962)
The converter clutch (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/56222273) is released prior to downshifting into manual second-second gear (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860212/56231659). Under normal operating conditions, the TCC (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860072/96356796/56220622) will not apply in second gear.

Pressure Control (PC) Solenoid Valve
Important: Some vehicles in Manual Second Gear (http://motoralldata.com/alldata/MOTOR~V33961540~C37356~R0~OD~N/0/77993956/78154671/92727705/92727707/34853741/34860071/34860212/56231659), at a stop, will start out in 1st gear, while others will have a second gear start. Refer to Vehicle Owners Manual.

The PCM output signal to the PC solenoid valve increases the operating range of torque signal fluid pressure in manual second. This provides the increased line pressure for the additional torque requirements during the engine compression braking and increased engine loads.

[20Xtreme02]

Is this Autocross that you're trying? I've been comtemplating that too. Let me know how it goes and what you think.

[rat]

Is this Autocross that you're trying? I've been comtemplating that too. Let me know how it goes and what you think.
I think that is what it is called. It is with cones in a parking lot. I'l let you know what i think about it though.

[rat]

Well, that was a blast. I think i was the second slowest vehicle there, but i was the only truck. I got faster on every run, i think my slowest time was 1:14, best of mid 1:08. The fastest car was around .57 something, an evo.

I ended up just leaving it in third.

My rear tires must hate me now, traction was an issue, however i was able to keep it going in the direction i was trying for. The guy that rally's normaly had the rear end out more than me, but his was a lot more controled(he made it look good), i assume his suspention setup had a little to do with that. I let 5psi out of the back, helped a little. It pushed when off the gas, and oversteared when on the gas, fairly neautral. I think poly bushings, and new shocks would help, lowering may help a bit as well, but i can't afford to go any lower due to the fluffy white stuff we get 4 months out of the year.

I don't think the roots blower is going to help my traction problems, but oh well. Now i just need to try the 1/4 mile stuff...

[Sparky2263]

Now i just need to try the 1/4 mile stuff...

That's what I'm talkin' 'bout........