The Elvis8tor Z28

iTrader: (3)

I hear it’s better to drag race the car in OD, because in D the over run clutch is on and it decreases the line pressure in the 2-3 shift point, and in time they say it may contribute to 3-4 clutch failure.

Example:

So is this true???

I’m thinking I should run my car in OD in all conditions. Because in Pontiacs it goes (1, 2, 3, D), so OD in Camaro’s is really “Drive“.

I don’t think it will hurt anything running my car in OD all the time.

What do you guys think about all this???

35th SS

iTrader: (2)

tried it before in OD.not good.always in D for racing 1/4mi.might try search for more info.burnt my 3-4 clutches when tranny was stock due to n2o.now upgraded to aftermarket parts inside.my 02.cent good luck.

RPM WS6

iTrader: (3)

I say use OD for everything. Just don't let the trans upshift into OD while doing a WOT run. That's the only thing I could see causing an issue.

Here's a great thread about this. The last 2-3 pages of the thread pertain mostly to OD vs D.

https://ls1tech.com/forums/automatic-transmission/562732-effect-rpm-s-4l60e.html

The Elvis8tor Z28

iTrader: (3)

At about what speed would that happen? I have 2.73 gears. I don't have to worry about it up shifting into OD in a 1/4 mile run do I?

Is there ANY harm whatsoever in running my Camaro in OD ALL the time.

It won't be ANY slower in OD will it?

I'm thinking about getting a B&M Deep Trans Pan to help keep my transmission cooler. Will that help a lot?

The reason I'm asking all these questions is because I want to take care of this car PERFECTLY!

BlackHawk T/A

iTrader: (3)

Was that on a stock transmission or a built one?

Computer controlled line pressure or vacuum modulated?

It seems this discussion may never die because of all the conflicting information. I was told that yes the overrun clutches come in in 3 but not at WOT. One thing you could do is bring it down to 3 to get out of overdrive, and when you go WOT bump it back up one notch. It won't shift but it will take you out of manual 3 which was used only to bring you down one gear. This is only done though because most builders I have seen information from all seem to agree that 4-2 is hard on the transmission, though I don't know if the rules apply to a built unit.

If you are racing the car from a stop, please just leave the car in OD. That is one of the only things you can't really debate. The other stuff applies to getting on it from a roll.

AutomagicLS1

iTrader: (18)

I always leave mine in OD when racing. Sometimes in the city ill leave it in 3

Red2000SS

2.73 gears make for a high ratio - I ran the numbers through one of the gear calculators on the web. Assuming a shift point of 6000rpm here is were each gear would top out:

1st: 55
2nd: 104
3rd: 168
4th: 240

Of course in a 1/4 mile WOT run, the torque converter is not going to be locked up so maybe drop those numbers by 10-15%.

Even so, there is NO WAY your car is ever going to need to shift into OD(4th) unless you plan on blowing through the traps @ 140-150+ mph

I have 3.23 gears in my car it never shifts into OD in the 1/4 mile.

performabuilt

iTrader: (25)

Of interest are the two links bellow , it is true that in the D or 3 position that the overun clutch does come on and apparently this causes a line presure loss on the 2-3 shift which may cause premature 3-4 clutch failure, you can note thats its on in this link,
www.performabuiltautomatics.com/dthird.html
and you can note in this one below that it does not come on during the 2-3 shift in the OD position
www.performabuiltautomatics.com/odthird.html
just a little information .
However it may be advantage to launch in the D position since the overun clutch being on in first will help to support the Input sprag but it turns off imediatly on the 1-2 shift.
So it would seem the best scenario would be launch in D then as soon as it shifts to second move to OD ,

Coonass350

iTrader: (19)

well everytime i race the 1/4 mile i just start out in 1st then upshift manually into 2nd,3rd, and then OD..is that bad on the tranny???? if so i had no idea

performabuilt

iTrader: (25)

well as i said thee is a distint line presure drop on the 2-3 shift when done manually , Its assumed this is because theres not enough fluild volume available to maintan presure and apply the 3-4 cluthc and the overun clutch at the same time ,I see not problem with shifting manually but i would do it like this
1-2 then time it before the 2-3 shift and jump to overdrive ,
I have considered and would like to see a presure test done on a trans shifting manually with the overun clutch feed blocked , this it would seem would eliminate that issue and at the same time for those who love to shift manually make this a non issue, Though the downside would be no overun or braking effect in any of the lower gears other than second when downshifting on decel

Coonass350

iTrader: (19)

oh okay i gotcha now, appreciate it

RPM WS6

iTrader: (3)

I wouldn't say most. Seems like quite a few have confirmed the oppsite. Here's how it was explained to me:

A 4-2 is easier than 4-3-2 because with a manual 4-3 shift, then auto 3-2 shift the band must release for 3rd and the overrun clutch apply, then the 3-4 clutch must release for 2nd, then the band must reapply for 2nd. However the auto 4-2 does not require the band release or the overrun clutch, only the 3-4 clutch release (multiple events vs one).

SSPEEDY

iTrader: (4)

If you're running a very high stall it'll be way before 140. Stock I remember my car would shift into 4th at around 135 (i may be off a little bit). After the stall, it would do it in the mid 120 range.

SSPEEDY

iTrader: (4)

I wish Vince@FLT would chime in

RPM WS6

iTrader: (3)

I think he means 140 in a 2.73 car. That would be about right actually.

performabuilt

iTrader: (25)

A little informations for those interested. (in od position)
1st=forward clutch, input sprag and low roller clutch holding
2nd=forward clutch, input sprag holding and intermediate servo appled(band on)
3rd=forward clutch, input sprag holding, 3-4 clutch on (direct drive through 3-4 clutch)
and intermediate servo released (band released vis 3rd clutch oil)
4th=forward clutch on, input sprag freewheeling, 3-4 clutch applied, overdrive servo
applied (band holding)
of note on down shifts.
4-3= The overdrive servo releases band (only change)
3-2= 3-4 clutch releases and intermediate servo comes on applying band

The operation on downshift with the least going on would be the 4-3 shift and in the same way the 2-1 shift since everything goes off except the forward clutch .
All these statements are true in the OD position

Now a 4-2 shift is a bit more complicated ,
4th servo releases band. 3-4 clutch releases,intermediate servo applys band so the band actually goes off and on momentarily during the shift some of you may have noticed on some cars not all that there can at times be a momentary rev bump on this downshift which can happen if the fourth servo and 3-4 clutch release before the intermediate sevo reapplys band , In bad cases it can feel like 4-1 then back to second quickly

Just a little info for anyone interested.

RevGTO

iTrader: (12)

Finally, an authoritative answer to the question that has so vexed this forum??? Even if the band releases and reapplies on the 4-2, I still can't see what is to be gained by a manual 4-3 followed by an automatic 3-2.

RPM WS6

iTrader: (3)

Understood.

However, 4-3 would not be the end of the scenario in a roll race situation. As stated by RevGTO:

After the manual 4-3, we'd be forcing an auto 3-2 going into WOT. So what we really need to debate is the following:

Is it easier to do a 4-2 while going WOT, or 4-3 manually under no load, then 3-2 while going WOT.

Also keep in mind that the overrun clutch will be applied in 3rd if we manually downshift to 3rd prior to WOT. That means less fluid pressure holding the 3-4 clutch while going WOT for the 3-2 downshift possibily causing slippage, correct? Hence the reason why we prefer OD for the 2-3 upshift, because no fluid pressure is lost to the overrun clutch.

The Elvis8tor Z28

iTrader: (3)

Will that put ANY extra wear on the transmission, or harm anything?

Because that sounds like a good idea!

performabuilt

iTrader: (25)

Ah the manual 4-3 probably would not be the same , since the 3-4 clutch is not being applied its allready applied and alls happening then is the 4th servo is releasing and the overun clutch being applied so since you wouldnt have two pistons trying to apply at the same time there probably wouldnt be that preasure drop present in the D 2-3 shift or the manual 2-3 shift ,Though I havent actually done a presure test on this it would make sense on the theory that the drop is due to the simultanious overun and 3-4 clutch engagment.
So Ideally which Im sure after one learned thee car on a roll launch it would be best to pull from od back to whichever gear you choose the upshift but always making sure you rather than allowing the 2-3 shift to happen in the D position quick skip the shifter to the OD position .
In otherwords when your talking a manual pull down the only thing you would need to avoid would be is the upshift back into 3rd when in the D position and you will be fine,

As for would the skiping D hurt anything no it wouldnt but it would avoid that presure drop on the 2-3 shift