4.88 vs 4.1

[rynoki]

I'm currently driving a 1988 (YN65 series) Hilux with a VP V6 engine and a T700 auto transmission. My diff ratios are 4.88 and I have 31in tyres. This set gives me roughly 3000rpm @100kph. I get 200-250 km's per tank.
My question is, will changing to 4.1 diff ratios give me a lower rpm @100kph and improved fuel ecomony?

Further down the track I'm looking at fitting 35in tyres with a body lift. Will this negate the change in ratios?

All feedback welcomed.

[hdj105]

I'm currently driving a 1988 (YN65 series) Hilux with a VP V6 engine and a T700 auto transmission. My diff ratios are 4.88 and I have 31in tyres. This set gives me roughly 3000rpm @100kph. I get 200-250 km's per tank.
My question is, will changing to 4.1 diff ratios give me a lower rpm @100kph and improved fuel ecomony?

Further down the track I'm looking at fitting 35in tyres with a body lift. Will this negate the change in ratios?

All feedback welcomed.

In a car the engine runs at 1800rpm @ 100km/h as a comparision.

Lower rpm will help fuel consumption to a point, however after that point it will work against you again, and finding that point may take some effort. If you are going to change to 35's I'd definately leave the 4.88 diffs until then.

Do you know if the torque converter lockup clutch is operating?

[rynoki]

Do you know if the torque converter lockup clutch is operating?

I have a suspicion that it is not. I have a Marks adaptor shift display in the cab that will display an "L" when it is locked. This I have not seen illuminate, even at 100kph.

[hdj105]

Do you know if the torque converter lockup clutch is operating?

I have a suspicion that it is not. I have a Marks adaptor shift display in the cab that will display an "L" when it is locked. This I have not seen illuminate, even at 100kph.

OK well that would be a good place to start. Fuel consumption will be slightly higher as you won't be getting 1:1 drive through the TC.

[rynoki]

Ok, regards for the heads up Hdj105, I'll have it checked out.

[surfseller06]

Have you thought about running it on gas? Don't no if it's the same in Vic. but in QLD you get back $2000.00 rebate.How big is your fuel tank? When I run on petrol I get around 300km to 350km per tank (65litre tank).I also put free whell hubs on,makes a small difference.I wouldn't recommend switching diff ratio's if your thinking about 35's..Mark

[rynoki]

Hi Mark,
I have thought about putting it on duel fuel, the $2000 saving is too good to ignore. I'll get the body lift first however so the gas conversion fittings will be correct the first time around.
I originally got a duel fuel quote before the government rebate was announced a couple of years ago. I think it was around $2000 then. You can bet it won't be now.

[surfseller06]

Yeah I got a quote for $2100, before the rebate I paid $3000. so only out of pocket a grand so it was not to bad.It pretty much works out to half price driving when on gas so it does 'nt take to long to get your money back..