Td42T, 5th gear overdrive help

G'day, been trying to find information for this for a while but can't seem to find anything for the TF plenty for ZD,

I have a GU ute on 35s with 4.6 diff gears, around town on the 95L tank it gets about 850-900kms but on the highway I get around 300-350kms I had the fuel pump replaced as mine was shot and that didn't help.

the only thing I can think off is around town it gets babied and I change around 15-1700 rpm and tops out at 70-80km/h, yet on the highway its non stop at about 2300 for 100km/h I'm looking at the 5th gear overdrive however its only a 10% reduction in TD42's and that hardly seems to justify the $1700 for the gear + $155 for the extended spline.

Has anybody done this on a td42T did the 10% make a massive difference I was really hoping to have it sit around 1800 but that seems like a bit of wishful thinking at the moment?

you have 4.6 gears, and in fifth at 100kph your doing 2300 rpm? Surely not. Mine in 5th sits on 2400 with 4.11's. I had 4.3's prior and it was doing around 2600 rpm. Somethings a miss there.

I'll double check on the weekend its in getting a service at the moment, but yeah still need it to come down, it revs way to damn high lol

I'd be getting the speedo checked aswell.

there could be other issues at play . what engine mods do you have , snorkel , 3' exhaust , airbox , bigger turbo / intercooler . is the IP standard . has it been tuned on a dyno ,a dyno can help show up other components that are not working right/efficiently at higher RPM .

Snorkel and 3" exhaust thats it, the no other engine mods didn't want to muck with that too much.

speedo was checked at engineering and also do a bit of traffic work so have checked it against calibrated speed devices

Something is not right. TD’s will happily sit at 2300 all day long. They hate anything under 2000rpm, but you have 4.6 gears so this will change a lot.
Mine is tuned at 170rwkw and 700nm on 33’s with 4.11 diffs and at 100kph it does 2400 rpm. I will see around 16L/100 on the highway. When I had 35’s it was just under 2200rpm.
Fuel usage will only change if I’m hauling a heavy load.
Get a gps app on your phone and see what speed it says compared to your Speedo.


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