gearbox ratio

scottyboy · 09-06-2005, 01:34 PM

Is there any way i can work out what ratio my gear box is? it on an xr2 and i was told when i bought it it's a sportsmaster if that helps? its a 2 hole deep water pick up box if that helps too?

Jon Fuller · 09-06-2005, 01:47 PM

most probably 1.87:1,but could be 2:1

the original 1986/7 XR2 (clamshel model) was I think 2:1, after that model, the std was 1.87:1, but some people re-ratioed the later model to 2:1

BluFin · 09-06-2005, 01:53 PM

If you got a good eye and ident the shaft, put it in fwd gear and turn the crank two revolutions see where the shaft ends up,
2:1 easy. 2 crank , 1 shaft
1.75 easy, 2 crank 1 3/4 turns shaft
1.87, my eys are shagged I couldnt see it !!!! but if it anint one of the other two !!!!! must be then 1.87

roofer · 09-06-2005, 05:33 PM

my box's a sportsmaster ive just changed the gears from 1.87 to 2.1.

BluFin · 09-06-2005, 06:35 PM

Quote:

Originally posted by BluFin
If you got a good eye and ident the shaft, put it in fwd gear and turn the crank two revolutions see where the shaft ends up,
2:1 easy. 2 crank , 1 shaft
1.75 easy, 2 crank 1 3/4 turns shaft
1.87, my eys are shagged I couldnt see it !!!! but if it anint one of the other two !!!!! must be then 1.87

Did I just work that out ass about face....... I deal with this later

BluFin · 09-06-2005, 11:13 PM

Sorry rotate the crank 7 times & you can see the angular rotation on the prop shaft. 7 is good as the % are higher and easier to determine

ratio crk trns psft rev

2 7 3.5
1.87 7 3.743315508
1.75 7 4

Jon Fuller · 09-06-2005, 11:34 PM

You been on the meths again John?

I reckon, rest your forehead on a broom handle, and walk round & round the handle till you fall over, that means it's a 1.87:1

BluFin · 10-06-2005, 07:56 AM

Meths is very groovy, stains your mouth barney Purple.

I'm going to try again as that cut & paste was shite.

Take out the plugs unless you are trying for a work out of biblical proportions. 2:1 is easy turn the crank twice & the Propshaft should make 1 turn.
To se the difference in the other ratios. you need more than two turns of the crank unlless you can eyeball the dfference between 1.06 & 1.14 turns of the shaft.
I would look for about 7 turns on the crank so a 1: 87 would show 3.74 turns
1.75 will show 4 turns of the shaft

Matt · 10-06-2005, 09:19 AM

Yeh. My 85 150 xr2 was 2:1. Also had the old preload pin on the top of the driveshaft.

Quote:

Originally posted by Jon Fuller
most probably 1.87:1,but could be 2:1

the original 1986/7 XR2 (clamshel model) was I think 2:1, after that model, the std was 1.87:1, but some people re-ratioed the later model to 2:1