OD or D

[Slow91z]

I'm sure this has been brought up before, but what is the difference between running the car in OD as opposed to D...I know it locks it out of Overdrive, but I have always heard that while drag racing to put it in D because it's easier on the tranny...this makes no sense to me...is it fact or fiction??

 

[d0n_3d]

D = use this when racing up to around 115 mph or so, then if you HAVE to, shift into OD

OD = economy gear, used for daily driving above the speed of around 40 mph...do not leave in OD when racing

 

[Slow91z]

But why can't I leave it in OD...it won't go into OD unless I'm going a lot faster in the Quarter then my car is capable of right now.

 

[d0n_3d]

if i recall...for some reason my car would shift from 3rd to 4th at around 90 mph or so at only 4400 rpms or something like that...that's why you would leave it in D (at least in my case...but then again my tranny was screwed up)

yes that does make sense, if your car doesn't even shift into OD at WOT before the end of the 1/4 mile then it doesn't matter if it's in D or OD...but to be safe i would leave it in D anyways if racing...on a stock tranny if it shifts into OD at such high rpms and high speeds it's MURDER on that gear and it WILL go out on you alot sooner than normal...ask me how i know that!

 

[denn454]

i've raced in both d and od with the close to the same times, i heard the shift points are different but i'm guessing thats a line of bs, knowhing who it came from it probably is.

 

[1KWIK6]

Leaving it in D or OD doesn't make much difference. Most stock GN BRF's will shift into OD around 100-103 mph. If you trap faster than that, you would benefit from holding it in D. Stock, there are only 2 clutches for OD! Additionally, the manual boost valve raises the line pressure when you manually select 1st or 2nd gear. I usually stage with the selector in '2'. I let the tranny shift 1-2 on its own, then I manually shift into 3rd at ~5,000-5,250 rpm. After I cross the traps, I shift into OD and coast down.

-HTH-

Ron

 

[Slow91z]

Originally posted by 1KWIK6
Leaving it in D or OD doesn't make much difference. Most stock GN BRF's will shift into OD around 100-103 mph. If you trap faster than that, you would benefit from holding it in D. Stock, there are only 2 clutches for OD! Additionally, the manual boost valve raises the line pressure when you manually select 1st or 2nd gear. I usually stage with the selector in '2'. I let the tranny shift 1-2 on its own, then I manually shift into 3rd at ~5,000-5,250 rpm. After I cross the traps, I shift into OD and coast down.

-HTH-

Ron

Really?? now that's good info...thanks everybody for the input.

 

[WE4]

Actually

Od is taking off on the sprag. But , you are not using the OR clutch in od.
I always would let go of brake and shift into od and let it shift itself. Also, on a footbrake car, I would suggest you use od for a 26" tall tire and a D with a 28" tall tire. I personally would use OD on both applications.
Trans would rather be in od if possible. You can always very easily add a third clutch to od if needed, however two is suffecient for alot more than you would think. There is actaully more clutch suface area on a 2 pack OD clutch than is in the WHOLE forward clutch combined.
Again, if the OR clutch is on you are dragging it in 1,2,or d.

Bruce
WE4
PTS XTREME

 

[Slow91z]

The Bruce has spoken...OD it is.

 

[1KWIK6]

Great information as usual, Bruce! One question, though. Please reread my post above where I explain how I launch and leave the selector in '2' until I manually shift into 'D' at ~5,250 rpms. If I were to leave the selector in 'OD' from the start, it would shift the 2-3 @ 4,900-5,000rpm's (which slows me down). How would you remedy that situation?

TIA

 

[WE4]

Well

two choices. Play with govenor, or do as you have been doing. That is fine. I was just asked an opinion question and gave my take. If that is what your car likes, by all means, keep it up!

Bruce
WE4
PTS XTREME

 

[d0n_3d]

so you are saying that i should race my car in OD??? i have a te-44 turbo, 50's combo...i just had my tranny rebuilt by vince janis and is it going to be ok to let it shift into OD at that high of rpms and speed? i know with a STOCK tranny the OD gear is very weak and does not like getting shifted into OD at high rpms...

i am running 26" tall slicks as well...

 

[d0n_3d]

i just did some searching and i see the best thing to do is just leave it in "D" until you hit 5000-5200 rpms and then if you still haven't crossed the finish line manually shift it into OD...also if you have a TCC switch...flip it ON about 2 seconds after you hit 3rd gear...

if you leave it in OD from the start...it has a tendency to shift early into OD like at 4400 rpms or something...i know that is true because my car did that all the time when my tranny was stock...don't know what it will shift at now but i am not gonna chance it...

basically just max out your rpms at every shift (stock motor cars 5000-5200 rpms)...

now if i had 28" tall slicks i wouldn't have to worry about shifting into OD because i would be crossing the finish line at or near 5200 rpms in 3rd gear...