a4 drag racing
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Joined: Mar 2011
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From: Maryland
I have read that leaving the tranny in OD will yield more consistent times than D, but it seems like a back and forth topic. For what it's worth I just left mines in OD when I ran it down the track this past summer, car ran great.
Ive done both before. never really noticed a difference. I believe the only time it might affect you is if youre trapping high enough to where the car will want to shift into OD. I'll have to pay closer attention next time and see if it makes any kind of difference
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From: Gainesville, Florida # of drag strips runs: ?!?!?
I run mine in overdrive. I used to run it in drive all the time until it hit the rev limiter on the two – three shift a few times. A former administrator here swore by running it in overdrive and claimed that it pushed more fluid through the lines to make the shift better. I run it overdrive ever since then and after 350+ runs never hit the rev limiter again.
That's on a completely stock transmission and converter with over 177,000 miles FWIW...
Derek
That's on a completely stock transmission and converter with over 177,000 miles FWIW...
Derek
Joined: Aug 2007
Posts: 24,241
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From: Turnin' Wrenches Infractions: 005
Quite the opposite. It uses more fluid in D hence the reason you hit the limiter because the excess fluid takes longer to get where it needs to go. Mine does the same thing, the 2/3 is a tad lazy in D when compared to OD. I tune my tranny for shifting in D to solve this issue. My trans builder said race in D, I think it is something about a low roller sprag engaging in D but not OD or something of the sort. I'm no tranny builder so excuse if my specifics on trans internals aren't spot on.
Mine was tuned and raced in D. RPM told me it would be stronger. It was bracket raced in the 10.5 second class and shifted at 7000rpm. Never hit the limiter,very consistant bracket car.
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TECH Fanatic
Joined: Jun 2006
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From: Elgin, Il
Shouldnt matter. Automatics wouldnt go in to 4th gear in the 1/4 mile anyways unless you got a stupid short gear in it. Ive never hit the rev limiter racing an auto, why would you? You should be shifting before the limiter. If you tune the shift points higher, then tune the limiter a little higher too.
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From: Gainesville, Florida # of drag strips runs: ?!?!?
Quite the opposite. It uses more fluid in D hence the reason you hit the limiter because the excess fluid takes longer to get where it needs to go. Mine does the same thing, the 2/3 is a tad lazy in D when compared to OD. I tune my tranny for shifting in D to solve this issue. My trans builder said race in D, I think it is something about a low roller sprag engaging in D but not OD or something of the sort. I'm no tranny builder so excuse if my specifics on trans internals aren't spot on.
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From: Gainesville, Florida # of drag strips runs: ?!?!?
I've only had the nuts to try it once.... 
I've run a 4L60 in all my LS cars and have had two real good trans builders. I have broken the sprag in my old 9sec Red Firebird 8 times on launch and i've broken the sprag twice in my 10sec Silver Firebird. That is when i used to run in OD and eventually found out that wen you run in OD it puts alot of stress on the sprag. If you run in D it uses an overrun clutch along with the sprag in low gear so its much easier on the sprag. I've never broken the sprag since running in D for the last few years. I bracket race every weekend (Fri & Sat) and usually make over 200 runs on both my GTO and Silver car each year.
I was told to start in first and shift using a light. It was explained that;
In manual low, the low/reverse clutch is engaged and aid the low roller clutch in holding the rear planetary stationary. Additionally, the overrun clutch in the input drum is engaged and aids, albeit slightly, the forward sprag in driving the forward sun gear. The only real disadvantage of launching in manual low, other than having to move the shifter multiple times, is that when you click 2nd and the PCM commands a 2nd gear shift, that low/reverse clutch has to release and get out of the way immediately so the rear planetary can turn. On a high RPM, high line pressure shift like a WOT 1-2, you may get a slight tie up as the band engages and the low/reverse releases.
On The Tree
Joined: Sep 2008
Posts: 148
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From: nashville
Race mine in D. I bracket race my gto, over 2000 passes in 5 years, Stock tranny lasted till i put in 3600 stall after 2 1/2 years. Reason i don't use OD is at finish line, if i rip on the throttle it shifts into OD and lose to much momentum.
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Shouldnt matter. Automatics wouldnt go in to 4th gear in the 1/4 mile anyways unless you got a stupid short gear in it. Ive never hit the rev limiter racing an auto, why would you? You should be shifting before the limiter. If you tune the shift points higher, then tune the limiter a little higher too.
^ very good thread.
So what if you do have a car that will go into OD in the 1/4? Can you launch in D then shift into OD and still have the overrun clutch along with the sprag? Or is there no more overrun clutch along with the sprag after manual shift into OD?
So what if you do have a car that will go into OD in the 1/4? Can you launch in D then shift into OD and still have the overrun clutch along with the sprag? Or is there no more overrun clutch along with the sprag after manual shift into OD?
I launched mine in d and when moving shifted to OD. Sometimes in D I would hit the limiter on 2-3 hence me shifting it. After that no more problems. Not the correct thing to do but worked for me. Never broke it.
