Upgrading the 410 Final Drive Ratio

John Keighley · #1 (**permalink**) 04-10-23, 11:42 AM

Thank you Andrew for your reply. This is the information I am looking for. sounds as if the 2.8 ratio may be what we need as the car generally will do longer runs. Fuel economy in the car's original state gave us 21-22 mpg but I hope we can improve on that, particularly as the tank is not that big!
Many thanks!
John K.

AndrewA · #2 (**permalink**) 04-10-23, 02:20 PM

Well if you think of anything you need - let me know. Re the attachment, Kevin who kindly looks after this forum will probably sort it out for you if you ask nicely!
I think - but could be wrong - that once you go into the 2's as it were on the ratios you need a different carrier to the 3's - worth checking.

David C · #3 (**permalink**) 04-10-23, 02:41 PM

I have just spotted that you say the fuel tank is not very big. Has your car had a smaller tank fitted? The standard tank seems huge when I'm paying to fill it!

David C · #4 (**permalink**) 06-10-23, 03:56 PM

Thank you for that. Loving the exhaust manifolds. Who made or supplied those?

I'm still keen to see some pictures of aircon compressor mounted on 410 engine as this is very different from the 411.

Thomas591 · #5 (**permalink**) 06-10-23, 04:07 PM

Uups, sorry that was a bit stupid from my side, of cause I am aware that your engine is different. Sorry for that.

The exhaust manifolds are from Spencer Lane Jones.

Regards

Thomas

AndrewA · #6 (**permalink**) 06-10-23, 04:21 PM

Updated figures (!) with GPS and a co pilot/scribe/second pair of eyes.
No o/d or lockup 72.1 mph 2400 rpm
O/d only 71.4 mph 1850 rpm
o/d and lockup 72.1mph 1650 rpm

David C · #7 (**permalink**) 06-10-23, 05:48 PM

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.

John Keighley · #8 (**permalink**) 10-10-23, 11:16 AM

Quote:

Originally Posted by David C

I have just spotted that you say the fuel tank is not very big. Has your car had a smaller tank fitted? The standard tank seems huge when I'm paying to fill it!

David, it's a standard tank - 18 gal but given the distances we sometimes travel, the contents disappear rapidly.

AndrewA · #9 (**permalink**) 10-10-23, 01:31 PM

Sorry to fail you but it's been wired that you can't engage lockup unless overdrive also engaged - I did try.

David C · #10 (**permalink**) 10-10-23, 08:02 PM

No worries, Andrew. Having had a bit more time to think I'm not sure how much it would tell us. I was thinking of the torque converter purely as a fluid coupling but there's more to it than that. At lower speeds my understanding is that input RPM and output RPM can be quite different with attendant torque multiplication but I don't understand is how this relates to efficiency and therefore MPG.
Enough pontification, it's time for me to hurry up that gearbox installation and then report before and after EFI MPG figures.

Sam410 · #11 (**permalink**) 17-10-23, 02:41 PM

My 410 has a 2.88 LSD axle. I am not sure if this was from new or from when the car was restored in the early 90s by Spencer Lane-Jones (it was his own car, not a customer restoration). Sadly my rev counter is wildly inaccurate so I cannot report accurate figures. I saw 24mpg on one trip this summer, but 21-22 is more common on a long steady run. Spencer also told me he fitted mildly faster cam, and the engine was rebored so I think is about 5.5 litres now. Still on the standard carb.