Upgrading the 410 Final Drive Ratio

[David C]

That's a really good result but very puzzling. I have always been told that there was only one overdrive ratio for the 46RH of 0.69:1 Yours seems to be 0.77:1 which is much better. Next time you are under the car please can you look out for a serial number? I will do a bit of research and try to find out where to look.

[David C]

I just calculated the ratio including lockup and it comes out at 0.68:1. Starting to make more sense...

[David C]

Further investigation tells me that there was only one ratio for the 46RH and this was indeed 0.69:1

This suggests that in Andrew's test there was far more slippage at 1850RPM than at 2400RPM. If anyone out there understands torque converters, slip, stall speeds etc they are probably marvelling at my lack of understanding and screaming "of course!" at the screen. If so, please enlighten us. i need to understand in order to arrange automatic switching of overdrive and lockup. It seems to me that in Andrew's example that switching in overdrive without lockup will introduce significant slippage with attendant heating of transmission fluid and loss of MPG.

Andrew -if possible at some stage please can you briefly switch in lockup only at both 1850RPM and 2400RPM and let me know how much the revs drop?

[AndrewA]

Of course re lockup and hunting for numbers if necessary!
May not be today as it entails trip to motorway - half hour each way - as no way can I (or even wish to try to) maintain steady 70 mph on New Forest roads !!

[Kevin H]

Given that comments relating to air conditioning have nothing to do with the 410 final drive ratio, I have transferred those comments to this new thread http://www.bristolcars.info/forums/8...ditioning.html