Crossing Line In Overdrive

[1234me]

Is it ok to cross the line in overdrive?

If I put 4.1 gears in I will be crossing in 4th gear.

does this mean that with 4.1 gears I will be slower than with standard 3.45 gears

I have 309 rwkw BA 4 speed auto

[turbotom]

Bear in mind that each gear shift takes a finite amount of time....

In modified autos, its not much, but still significant.

The time taken to shift is a period you are NOT accelerating, but maintaining velocity (the academics will say you are losing speed, but it won't be significant)

If you are only requiring 4th gear for the last 10 metres or so, you'll probably post a similar time holding 3rd.

If you can safely increase your upper rpm limit, there is some more room to hold 3rd gear over the line for a better time.

Ideally you would want to negate the need to make an additional shift from 3rd to 4th. Also, there is a heck of a lot stress on the gearbox changing into 4th at full noise.

The torque is applied via the band to the drum on the 3-4 change, and there would be a heck of a lot of slip changing into 4th at that load.

Maybe if running taller slicks, which balloon out at speed, then the 4.1 gears might be beneficial for traction and holding a higher trap speed in 3rd, but the 3.45 diff with a high stall converter and some sticky 17" MT tyres will get you down the quarter mile pretty briskly.

just my viewpoint.

tom

[Ninka]

Pushing you luck, as 4th was never meant as a power ratio.

Mine with 340 rwkw started slipping in 4th, so I had to get off the accelerator, and 3rd was too short, even with 3.45 ratio, so you are fu*ked

4th may hold for a while, but don't expect it to be too long

[MYWPN]

remember 4th is only used as an overdrive so its not made to take alot of full load power runs, so I would be trying to gear it for top of third gear (higher wall tyres, rev limit etc)

Edited 22/03/07 08:13 AM by phase3ute