[Cwils1992]

Just bought a '97 "coily" Sierra with '99 baleno engine in it. Great 4wd rig but need it As a daily driver as well and it's geared too low. Runs at 4200 rpm at 100km/h... It's got a '91 rebuilt transfer case with 4.16 reduction gears in it and running 30" bighorn tyres. Trying to find a way to keep great 4x4 capability while making it less rough on the engine for everyday use.

Cheers

[greenzook89]

That's actually pretty good. Mine revs at 3600 rpm @100 and its painfully slow in 5th. Suzuki engines love the revs, I wouldnt stress too much.

[Cwils1992]

Gotta take it on a long trip and sus out fuel consumption. Travel a fair bit and not keen on forking out $90 every 350km. Was thinking would changing diff ratio's even it put a bit?

[atari4x4]

the only logical solution to your problem is to fit bigger tyres... it's a win win situation.

[greenzook89]

Cwils1992 wrote:

sus out fuel consumption. Travel a fair bit and not keen on forking out $90 every 350km.

Even revving at 4200 you shouldn't be using 90 bucks worth of fuel for 350 kms. I get 9l/100 on mine highway driving (including staying in 4th as 5th is useless on hills) and only costs me 50 bucks to fill up from empty.

[alien]

are you sure the RPM reading is correct? wouldn't be too hard to put the wrong resistor in there during the conversion and have it read wrong...

perhaps the tyres are worn? a brand new 30" already measures 29" - take a lot of tread off and you'd be down to a 28 almost =)

[Cwils1992]

Atari Spoke to a few tyre shops and they reckon I'd be pushing shit uphill fitting bigger tyres because of the added width. For only about 300 rpm drop roughly. Nah tyres on it are over 80% tread and I'll look into the resistor although going on noise and feel I reckon the rpm would have to be pretty close. Greenzook it's got a custom 65litre fuel tank in it.

[alien]

what rims are you running for the tyre shop to be concerned about width?

as far as RPM goes - if i wasn't looking i'd swear 4500rpm sounded like 6000rpm in my sierra... most i've revved mine is around 7000rpm and the limited never kicked in or anything... it sounds remarkably the same from about 4500 onwards.

are you sure the tcase isnt a NT one with lower gearing?

[JrZook]

$90 of fuel = how many liters?

Assuming fuel is around $1.55/L thats equivalent to ~58L which is roughly 16.5L/100km. Unless you are flat to the floor everywhere, towing a trailer or have been driving in the sand for most of those 350ks there seems to be a possible issue.

Running 30's with a G16B and 4.9:1 tcase my onroad fuel economy was routinely around 10L/100km.

[alien]

i'm suspicious of my sierra's fuel economy at the moment - i THINK the choke is stuck on as its quite flat up to 3000+rpm and using more fuel than normal. Hopefully caused by blocked coolant hoses and not something more serious.