420G Auto upshift info required

[acbautomotive]

Hi All
I was recently doing some tuning work on a 1968 420G with High comp engine and triple SU's fitted with the Borg Warner model 8 Auto box.
Following the tune up I took the old girl for a drive but was very surprised at the high level of revs for the relatively slow speed, I wondered if the car was actually changing up to its top gear. I would be very grateful if anyone could provide me with typical upshift details for each gear, ie 1st up to X RPM at Y MPH etc.
Thanks in advance. Tony

[oldtimer]

Tony ,
Have just looked in my 4.2 mk 10 service manual which I am reasonably sure has the same set up as the 420G.

Tis a bit late for the 'ole boy so shall continue tomorrow

Yes, I have the change points

Oldtimer

[oldtimer]

To continue,
This service manual refers to BW type 8 Auto box

selector throttle upshifts downshifts
position position 1 - 2 2 -3

D1 - min 6-7mph 10-12 mph
full 31-36mph 54-58 mph
kick down 42- 46mph 66- 73 mph

D2 min --------- 10-12 mph
full --------- 54-58 mph
kick down --------- 66- 73 mph

I have not included the downshift data.

Performance Data at the front of the manual refers to 3 different axle ratio, I seem to recall that axle ratio 3.54 was common across several Auto models. There should be a tab under one of the axle rear cover retaining bolts, this has a number something like 13/ 64 ( now that's a real guess) but 13 refers to teeth on pinion and 64 teeth on crown wheel but you probably knew that.
Divide 64 by 13 will give the axle ratio fitted.

That's ya lot for tonight- time for bed

I hope that answers your question

Oldtimer

[oldtimer]

Sorry the format changed when I pressed SUBMIT
I hope you can make sense of it - come back if not

[acbautomotive]

Many thanks for your great reply.
Based on a high diff ratio and your change up data, I could well have been at the point of up change in second at 4000 rpm and only be doing 50MPH.
I will get this 420G back in to verify this. I was probably just not going fast enough !!
It was a joy to spend the day with this lady...........
This car came in with emissions CO of 12% and still ran. It was much happier at 2.5%.
H Carbons went from 1600 to less than 200, Although the cold start device on the triple SU's is quite maintenance free, it does not exercise the jet movement as on manual choke cars,
Many thanks for taking the time to provide the info on this vehicle and completely answered my question. Hope to meet you at Kemble at some time.
Tony
Thanks Tony