Help with gearbox ratios please

[ronmidg]

Struggling to understand T4 gearbox final drive ratios (cos I have 2L motor on a 3 rib box in the bay and its slower than my stock 1.6 split)

Have copied this from the parts emporium gearbox codes and ratios page


17/18/2000 4th gear 0.89:1 with Final Drive 7.34:1

Reverse 3.80 upto chassis 2112276560 then 3.61

Final drive 5.375 through chassis 213 2300 001 then 4.857 from chassis 214 2000 001

there are three final drives mentioned 7.34, 5.375, 4.857

Do any of these numbers relate to the 3, 4 and 6 rib gearbox descriptions that are used on the forums?

if the 7.34 is 3 rib and the 4.857 is 6 rib it implies a 51% increase in speed at same rpm, so my current 49 mph at 3000 would become 74, is this consistent with what other people find with the 6 rib box?

 

[ronmidg]

more information

the 7.34 is tooth numbers not ratio so all the above is rubbish.

Haynes lists two ratios for the 72/79 transporters CA 8/43 teeth 5.375 ratio, and CN 7/34 teeth 4.86 ratio.

My next Haynes is the water cooled 82 to 90 which lists 4.57 and 4.86 no teeth numbers.

so is 4.57 the 6 rib CP gearbox? and 5.375 the early 3 rib? in which case the swop would increase speed at a rev number by 17.6%, giving 57.6mph at 3000rpm, that is still slower than the split :?