I have 3.73 gears right now on my A4. How bad should I feel about letting it shift into OD? What's this myth that OD can't be used? What's the basis behind it? I mean I instinctivly feel the same way but is it truely a logical practise to avoid OD?

 

Overdrive creates heat. Overdrive is no 2 pairs of gears like the regular gears, it works with planetary gears.

Personally, I think that if it isn't a hard shift, and isn't for prolonged periods it should be OK. But I'm not mechanic.

 

i have heard this as well and it does make sense, but i have no clue if its true or not. i do know that the only time i use OD is when im on the freeway. i figure theres no need to have the tranny shift into OD all the time driving around the city.

 

I have a freind who ran 9.90 on a stock gn block and he would go into OD. He said going into OD would give him some more mph. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Steven

 

From what I just experienced at top speed and seen in the PCM tables, the stock program does not let you go into OD at WOT. As long as you have your throttle to the floor, it should stay stuck in 3rd. If you lift off the accelerator for the normal shift tables to take over, it will be allowed to shift into OD.

GM has my stock WOT shift speed set at 254 MPH and the Normal tables are set at 254 for throttle positions at 50% and greater. My Superchips programming left it the same way. And for the quarter-mile, this is what I'd want. The car would shift just as I went thru the traps, but I didn't realize it was ONLY because I was starting to ease the throttle. <img border="0" alt="[whiner]" title="" src="graemlins/gr_cry.gif" />

When I had the 2.73's in there and no SC, I ran 142 MPH while still in 3rd gear (ran out of straight road). With the SC and 3.73's, I thought for sure I'd fly. I got to over 130 MPH at greater than 6000 RPMs and was stuck. Like a fool, I kept it there knowing it should shift any moment...

Now, I think I messed up my motor. I raced it shortly after that. (I was on my way home to race a Firebird with a 455 CID and wanted to see how it would top out with the SC). An hour or so after the top speed run, when I got in my hometown, I got on it and when I got off the throttle, the car cut off. It acted like a car that flooded out, but I got it started back up after some cranking.

I beat the 455 Firebird easily (he wasn't built up like the other 454's I ran). But, on each run, I was was blowing some smoke. When I got home that night (two hour drive), I'd lost coolant. I haven't been to the track in a while. But, on the measured quarter mile at that certain location <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> , my trap speed was nine or ten MPH lower than it used to be.

All that talk about how I'm running hotter than I was last year... well, it may not just have been the heat; I'm seeing white smoke on a cool morning, and if I WOT it now, it even spray's water onto the underside of the hood.

I've parked it and if GWP is finished R&D on my 422, I asked them to go ahead and ship. I didn't mind them keeping it as long as they liked to tweak and tweak. But, since I'm definitely on the bench, Kenny is willing to go ahead and send me what he's got. <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" /> (Thanks, Kenny.)

I will start taking it down this weekend so I can get the SY3500 changed over to a PY3400E before the motor gets here.

Well, I raced the car before the SC from about 30,000 miles until I put the SC in at 66,000 miles and now I've parked it at greater than 80,000. How far could I have gotten it to go if I hadn't been stupid? <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />

<small>[ September 01, 2002, 07:46 AM: Message edited by: Black LS1 T/A ]</small>