130mph, 26" tall slicks, what diff gears should I have?

[Brett SS]

Hey guys,

Last time out I ran 10.75 at around 129-130mph with 26" tall slicks but that was with 4.11 gears and shifting into overdrive before the line. Would I also run out of 3rd gear with 3.73's if I only want to rev to around 6700rpms?

I would like to hear from people running similar mph etc and see what rpms they are crossing the line at. I don't want to go to the effort of swapping back to 3.73's if I am only going to have to swap later on. I can also look at swapping to a 27" tall drag radial or 27.3" tall slick if needed as well to give that extra head room at the end of the track.

[LS1TOY]

http://www.hotrodpitstop.com/tools.html

Have a look. Might help you out
Jake,

[Brett SS]

http://www.hotrodpitstop.com/tools.html

Have a look. Might help you out
Jake,

Thanks for the link, with guessing a 7% converter slip it said I would be right on the 6700rpm limit I wanted with 3.73's and 130mph. Have people found that this works out about right?

[ittwgn]

try this one cheers
http://www.wallaceracing.com/gear-speed.php

[dogsballs]

brett what did you end up doing with this?

i'm in a similar predicament. running fraction slower 11.4@122 with 1.63 (first outing so a bit to improve), 4.11s and 4500 convertor with 235/60/15 just hitting 4th over the line. we've got first change at 41kmh and limiter at 6900. going to push 2-3 shift a bit higher and leave it in 3rd, however not super keen buzzing the limiter.

the calc's above suggest going to a taller tyre
anyone go from 235/60/15 to 255/60/15's

[Brett SS]

hey mate,

I've ended up buying some M/T 28x9" slicks and going to run them with the 4.11's. Hopefully that will be enough to stop me hitting overdrive but it will still be close.

One thing that is helping me out is that I lock up my converter at the top of 3rd which gives that extra few hundred RPM's in that gear.

[dogsballs]

yeah, dale from CHE suggested that. we had a go at doing it, but with EFI live a little tricky as you have to estimate speed, which then we didn't know. but now would be 120mph or ~180kph. also bumped in Jason from Dominator when i was down at DTM automatics last week and asked about this and he said it can be done, just really shortens the life of the convertor.

PM'd M12 about this and he thinks persist with 235/60/15 as it throws everything else around, not beneficial with this hp.

so going to bump the 2-3 shift kmh, then leave it in 3rd maybe try the convertor lock-up as well.

[HRT 8]

DB, the TQ as Jason would have indicated doesnt like being locked up under WOT.
G&D used this technique on a mates car (trapped at 123mph with 3.9's) some time ago with an u/k convertor. Worked quite well and the convertor is still going strong AFAIK, although very little/no track use now.

[dogsballs]

thats the thing, we're trying to push the envelope of these things. heck, we need to push things a little, to make the improvements. i know this thing wouldn;t be making the hp without 100thou off heads and resulting 12.0:1 comp, but pretty much everyone said don't do it. same as a 6900 rev limit. same with the lock-up convertor thing, there are some dyno operators who run it in 4th to get good numbers. suppose they are covering their back in case it goes boom!

[STATIE]

Lot of debate about the lockup either at the top of each gear or just the top end of third - me personally - done it for years - never cooked a converter - it works.
One thing I will say is though - certain converters wont like it.

[IJ.]

thats the thing, we're trying to push the envelope of these things. heck, we need to push things a little, to make the improvements. i know this thing wouldn;t be making the hp without 100thou off heads and resulting 12.0:1 comp, but pretty much everyone said don't do it. same as a 6900 rev limit. same with the lock-up convertor thing, there are some dyno operators who run it in 4th to get good numbers. suppose they are covering their back in case it goes boom!

Could always buy one of these if you're "serious"

" MegaRaptor-2L " This is our 10 1/2 inch Billet Converter with a Billet Clutch Apply Piston that will not flex. It has a very large carbon clutch with 29.258 square inches of clutch lining. The torque multiplication rates can be ordered in 2 to 1, 2.5 to 1 or 3 to 1. The torque multiplication of this converter will deliver an increase of up to 50 horse power to the rear wheels. The MegaRaptor-2L with its carbon fiber clutch will withstand power levels of 1000 horse power. This 10 1/2 inch converter can be ordered with stall speeds of 2000 to 5500 RPM. Fits 4L60E, 4L65E and 4L70E transmissions, 1998 on with a LS1 type motor. Will not fit 2005 Corvette, Call. Cost $795.00

[dogsballs]

thats a big convertor!!

[blnls1]

Hey Brett ss and dogballs,

I know this is an old thread. But how did you guys end up with tyre, converter, and gear choice?

I'm fairly new to the drag scene and only have a handfull of passes under my belt with a best of 10.91@127mph with lowerd rear springs 3k converter and 3.7:3's and 235/60/15 MT drag radials. I'm going to switch to a 26x8.5" slick and front runner's and throw some 90/10's in the front and some standard FE2 springs and shocks in the rear. but am looking for a solution to not hitting 4th gear before the line. So just wondering what worked for you guy's?
Cheers.

[blnls1]

Dogballs,

Dont recommend 4.11's.....................Dont want to regret selling you that diff!!! Maybe wouldn't have lasted many passes anyway being pintara gear's.....

[ittwgn]

hi mate if you were going to stick to a radial would of said step up to a 255/60/15 et street which is 27 inch !!!would help on the launch with more sidewall!!!! going full slicks !!! either step up like me and brett ss did and fit 28x9 slicks which actually measure 27.3 inch!!!!! or 3.45 diff gears!!!! with 26 inch radials i was maxing out 3.73s at 6500 rpm at 134.8mph fitted 28x9 slicks went 140.8mph then went 3.45s went 142.8mph limited testing cheers