Speedo, lets try to stump the experts with this one :huh2:

[Sir Plug]

Hello all,
Just a random "problem" that no local mechanic can make sense of here so let see how you lot all go with it,

2 hilux surfs, both 2l-t (both non efi in other words) both have R150f gearbox and yet mine does 2900rpm at 100kmh and my mates one only chugs along at 2400-2500rpm at the same 100kmh speed.
The only difference between the trucks is ones a 1990 and the others a 1989 but I doubt this matters much.

Weird of what? Wheres the logic in this?

PS. they both also actully 100kmh as verified with gps.

Cheers, not really important just bugs me not knowing why my trucks sucking through so much more diesel than mates on long runs because of this.

What mechanic have you been taking it to........go and see Scott at Rakaia Service Centre.

[Kiwisurfing]

still confused about this gearbox slip thing if anyone can shed some light on this for me? would have thought its a manual so once in gear thats it and its directly connected to the wheels, asides from the clutch of course but I just had it replaced 2000kms ago so bairly run in yet.

[Sir Plug]

When you say you both have the same gearbox, are you going by the tags on the engine bay or by the gearbox numbers, themselves??

[Albannach]

I was hypothesising that something in the gearbox was 'slipping' (assuming it's an automatic) too much. Apparently, our automatic gearboxes are similar to a pressure regulated variomatic gearbox, that is that rather than changing gear positively, the gears slip in gradually. Too much slip will give a higher engine speed for a given road speed, in the same way that a slipping clutch on a manual gearbox would allow the engine revs to rise, but not the road speed.

The OP's issue is the final drive ratio, it's different on both trucks, therefore different engine speeds for similar road speeds.

As for the speedo; the ECU controls that, not the 'speedo drive'.

EDIT: Just noticed that both trucks are probably cable driven speedos. I assume the speedo drive gearing will be different, a quick check of an EPC would be prudent.

[Kiwisurfing]

Have gotten gearbox info from engine bay tags, supposibly both should be 5 speed manual R150f boxes, mabey ill have a look at actual gearboxs tomorrow but they should be origional. the older one (1989) does have a rather bad speedo wobble under 30kmh so mabey the speedo is way out, but that would also mean the 2 different gps units have a different actual 100kmh speed?

Argh might just chalk it up to my trucks dam old and unpredictable, mabey even the engine rpm sensor in one of the trucks is giving up to, its old mabey we just leave it at that

[Sir Plug]

The OP's issue is the final drive ratio, it's different on both trucks, therefore different engine speeds for similar road speeds.

Correct......I believe this truck started life as a petrol................

[Kiwisurfing]

Blooming heck you are on to it
Yes my truck did start life as a petrol v6 sucker, hence the 4.5 diffs
But anything and everything from the donor 2.4 came out and into my truck right down to the loom and dash so speedo shouldnt have been giving me troubles with acuracy and gps matches it.
The engine bay tag info is from the donor as mine dosent mean stuff all anymore but to clarify the donor matches the other truck I mentioned before

[Sir Plug]

Blooming heck you are on to it
Yes my truck did start life as a petrol v6 sucker, hence the 4.5 diffs
But anything and everything from the donor 2.4 came out and into my truck right down to the loom and dash so speedo shouldnt have been giving me troubles with acuracy and gps matches it.
The engine bay tag info is from the donor as mine dosent mean stuff all anymore but to clarify the donor matches the other truck I mentioned before

Do you know what size wheels and tyres the old truck had, was the speedo drive calibrated to match said tyres, are the transfer box's the same?? First thing to check in daylight is that you have the right gearbox.......

[Kiwisurfing]

Ild say the donors speedo drive was tweaked

well you guys are great, I never would have thought my diffs would have had such a difference in engine speed vs road speed but proven me wrong.
cheers all for youre help now im going to save up for some bigger tyres just because I know it will handle it now.

On another note bigger tyres will bring revs down a little would this save me any diesel or would the extra load take away any benifits from lower engine speeds at 100kmh having to turn bigger tyres?

[Rustinho]

Ild say the donors speedo drive was tweaked

well you guys are great, I never would have thought my diffs would have had such a difference in engine speed vs road speed but proven me wrong.
cheers all for youre help now im going to save up for some bigger tyres just because I know it will handle it now.

On another note bigger tyres will bring revs down a little would this save me any diesel or would the extra load take away any benifits from lower engine speeds at 100kmh having to turn bigger tyres?

Bigger tyres will kill your fuel consumption figures.

I used to get early-mid 20s mpg and now I get about 17mpg.

(used to get up to 10.6 km / litre, now 7.2 km / litre to give you a rough idea)

EDIT: I should add that tyres went from 265/70/15 on alloys to 33/12.50/15 on steel modulars.

Also, now on my "to do" list is a set of 5.29 gears to try & recover some of the characteristics lost in going to 33s! They seem to be about US$100 a pop so not overly expensive...

[Kiwisurfing]

cheers for that rustinho, bit of a shame about the fuel consumption but im still going to have to get some bigger tyres anyway, currently running stock size 30-9.5.15s which are way to narrow for the heavy beast and keep digging down into shingle and river beds.
And as you guys probbly know once youre dug into soft shingle its rather hard to get out again ha ha I was lucky there was a farm nearby and payed the farmer to tow me out with his tractor