Diff ratios

[jrmc47]

Hi all has anyone used the 6g74 auto diffs in a 4m40t manual...any problems? How does the diesel go with the V6 ratios?
Cheers in advance

[erad]

I don't know specifics, but if you look at the red line o-n the tacho of a petrol vehicle and compare it with the diesel equivalent, you will see that it is 6000 R/min vs 4000 r/min (give or take a few RPM. This means that the diesel engine would be screaming flat out at something like 100 km/h. it would get to 100 very quickly however. In other words, the vehicle would be horribly undergeared.

[Martynhpajero]

The diesel diff ratios are 4.9.
The auto petrol diff should be 4.63.
Should drop a couple hundred RPM at 100kmh. I'm going to do the same to my NL 2.8 at some stage. I have a factory locker from a NJ exceed in the shed...

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[jrmc47]

The reason I ask is because i am doing central Australia with a camper trailer and I know you shouldnt tow in 5th gear so a drop of a couple of hundred rpm in 4th will be ideal I think

[jrmc47]

I should add that I did convert mine from V6 auto to 4m40T auto ...so retains the v6 diffs cos they are the same ratio as the auto diesel ones...its twin locked so I dont want to have to change them when I convert it to manual...if that makes any sense at all

[pharb]

Manual box behind the TD had a higher 5th gear as well as the 4.9 diffs.
I think 0.76 vs 0.81 (don't quote on the 100ths!!).


I can't recall what engine revs at 100km/h in my 4m40t. Tacho hasn't worked for about 5 years. Also have 32" tyres with corrected speedo, so a bit hard to compare with factory specs.

[pharb]

Have done 2 trips from central Gippsland to Kunnanarra towing 1.5t camping trailer, and maximum GVM (and a "tad" more).

Towed in 5th gear wherever it would pull 5th gear. Sat on around 90km/h outside of Vic where I wouldn't hold up traffic.

Averaged about 14L/100km for the trip.

The gearbox is nearly as big as a Patrol 'box, and a huge improvement on the 'boxes in the Gen 1s.

Gearbox is still quiet. Syncros fairly tired.

[Martynhpajero]

Mine with 265/75/16 tyres revs at 2750 at 100 kmh GPS speed.
I don't think it's a drama towing in fifth. That manual gearbox is pretty solid. Towing a camper trailer I usually only changed down to fourth when the EGT's were getting too high.

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[jrmc47]

Have done 2 trips from central Gippsland to Kunnanarra towing 1.5t camping trailer, and maximum GVM (and a "tad" more).

Towed in 5th gear wherever it would pull 5th gear. Sat on around 90km/h outside of Vic where I wouldn't hold up traffic.

Averaged about 14L/100km for the trip.

The gearbox is nearly as big as a Patrol 'box, and a huge improvement on the 'boxes in the Gen 1s.

Gearbox is still quiet. Syncros fairly tired.

thats what I am going to do as well ...my camper is 1.5 tonne tare too 2 tonne loaded...just took the donor car for a quick drive and the box is whisper quiet...synchros are excellent...so pretty happy
how were your EGT's?
cheers

[pharb]

EGT???

No idea. Would need a guage for that.

EGTs must of been acceptable. It's still going 7 or 8 years later

[Meth'd_up_Mitsi]

If it's still stock boost and fueling then high EGT's shouldn't never be an issue.. I've got the boost wound up and fuel turned up so my EGT's do get quite high. But I've got water meth injection that knocks up 300°C out of the temps..

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[jrmc47]

If it's still stock boost and fueling then high EGT's shouldn't never be an issue.. I've got the boost wound up and fuel turned up so my EGT's do get quite high. But I've got water meth injection that knocks up 300°C out of the temps..

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Does the water /meth injection do anything for engine temps as well?????

[Meth'd_up_Mitsi]

As in elevated temps over normal? Never.. engine always sat on normal temp. Water meth injection is unbeatable when it comes to towing. I could tow a 4wd on a car trailer up the gateway bridge in 4th no worries and EGT's would never get above 350-380°C. Would do it in 5th but it drives the cylinder pressures thru the roof.

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[jrmc47]

Surely someone has done this...come on guys

[jrmc47]

As in elevated temps over normal? Never.. engine always sat on normal temp. Water meth injection is unbeatable when it comes to towing. I could tow a 4wd on a car trailer up the gateway bridge in 4th no worries and EGT's would never get above 350-380°C. Would do it in 5th but it drives the cylinder pressures thru the roof.

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can you give me a bit more info on the water / meth please?