What rpm for 1-2 shift?

MilesnMiles · Post by **MilesnMiles** » Sat Sep 22, 07 6:23 pm

Whilst racing today, I noted that the 727 shifted 1-2 at something around 4700-5000rpm. Is this how it should be given that the botton end is only good for about 5,500rpm(?)?.
wondered if the convertor could be slipping allowing the engine to rev highly without transmitting the power. Even so, got a spirited wheel chirrup between shifts.

Dave-R · Post by **Dave-R** » Sat Sep 22, 07 6:56 pm

In drive the transmission will shift when it feels like it. You can alter the exact rpm by lengthening or shortening the kickdown lever. The longer the lever the higher it will rev.
But axle gears and load on the engine will effect what rpm it shifts at too.

5000rpm is nothing. Even for a stock engine. If you are looking at a factory tach it will not be reading right anyway. Most are WAY out.

This chart shows what MPH you would expect a trans to shift at in "drive".

MilesnMiles · Post by **MilesnMiles** » Sat Sep 22, 07 7:22 pm

actually Dave, now you mention in, its probably in the kickdown lever as 1-2 is quite a gap before it shifts. Certainly going a lot faster than 30-40mph

Tach is autometer, big aftermarket jobby.

Anonymous · Post by **Anonymous** » Wed Sep 26, 07 2:19 pm

yea have a play about with the kick down.
i was revving the scamp to abou 5500 at the pod and it was fine

MilesnMiles · Post by **MilesnMiles** » Mon Oct 01, 07 10:20 pm

Mick, i stick it in 2nd which provides a 1-2 shift and then manually shift it from 2-3 at approx 4,500-5,000rpm (depends if i bottle out!), this gave me a recent best of 14.3 with the same traction problems that you mention

Dave-R · Post by **Dave-R** » Tue Oct 02, 07 9:17 am

You need to hold it in first as well to get a better 60ft time and that way you will get a much better ET. If it is auto downshifting to 1st anyway you are not gaining anything by starting in second.

MilesnMiles · Post by **MilesnMiles** » Tue Oct 02, 07 7:11 pm

Mick, a tad shy of 98mph terminal, and the gears are open with a stock convertor. Motor is rebuilt with hypertumlarky pistons, XE262 cam, rebuilt and lightly ported heads, plus the usual ignition, inlet, carb stuff and TTI exhaust. Tyres are also 225 x 15 rear. I cant get traction if i wind it up!

Dave, racing last week I started car in postion 2 (Drive 2) and it starts in first gear and upshifts automatically into 2nd at about 5,000rpm which chirrups the wheels and then i manualy shift into top when i'm ready.

Dave-R · Post by **Dave-R** » Wed Oct 03, 07 9:40 am

MilesnMiles wrote:Mick, a tad shy of 98mph terminal,

You should be able to run a 13.9 with that mph.

MilesnMiles · Post by **MilesnMiles** » Wed Oct 03, 07 1:51 pm

Thanks Dave, whats missing currently besides, tyres, traction control, convertor, technique

?

Dave-R · Post by **Dave-R** » Wed Oct 03, 07 2:17 pm

Because of the gear ratios you need to shift at a higher rpm on the 1-2 shift than on the 2-3 shift.

Try taking her up to 6000rpm on the 1-2 and 5500 on the 2-3.

Or. Put your engine spec into desktop Dyno. Hit the "print screen" button on the keyboard and paste the resulting image into whatever image viewing softwear you use so you can save it.

Then send the gragh to me and I will tell you what your ideal shift points for each gear should be.

MilesnMiles · Post by **MilesnMiles** » Wed Oct 03, 07 2:22 pm

I'll have a look at the Desktop Dyno, dave. That aside, my rods and bolts are stock, probably not wise for 6,000rpm?

Dave-R · Post by **Dave-R** » Wed Oct 03, 07 4:04 pm

I don't see why not. They used to put the red line at 6500 on these cars.

I have always revved that high on my 440. Even before I fitted new bolts.