NP DID Auto 75 profile Tyre size and torque converter

[bernardpotatoe]

Hello All,
I have just upgraded from a 99 NL manual petrol to NP DID auto. I had 265/75-16 Toyo OPAT AT's on the NL and found them very good. The spare of the NL is still new and I have it. I was going to purchase 4 more the same to fit on NP (was a Toorak tractor with HT's (bald)), but have read somewhere about the torque converter lock up having issues with the larger diameter tyres. My brother has a petrol NM auto with 265/75-16's and seems to have no issues.
Thanks in advance
Bernard

[Muzza]

[QUOTE=bernardpotatoe;469]Hello All,
I but have read somewhere about the torque converter lock up having issues with the larger diameter tyres. My brother has a petrol NM auto with 265/75-16's and seems to have no issues.

There has been many posts on this, heres a summary
1 Larger tyres will cause the vehicle to have reduced lock up time
2 Fuel economy will be effected
3 Spare wheel cover wont fit
4 Its a diesel issue only, this is due to the high torque and high gearing the DID has, Locking up and loading the transmission at low RPM ( below 2000) will cause damage due to torque harmonics (this is a major issue in line haul trucks)
cheers
Muzza

[psproule]

5 75's are outside the 15mm allowable legal increase in diameter and could possibly void your insurance in the event of an accident. List them on the policy.

[Adza]

Depends if your state has adopted the new-ish code.

[nj swb]

5 75's are outside the 15mm allowable legal increase in diameter and could possibly void your insurance in the event of an accident. List them on the policy.

Don't leave home without it!

[allanmac]

As Muzza, said I have also heard this from many people & it only relates to the diesels for some reason. By the same token, I have just fitted some 75 profile tyres on my NL & can notice the difference even with the small diameter change. My 'play tyres', same size, are on 16x8 steel rims & the loss of power is quite evident, but I didnt expect to suffer the same with my standard alloy rims.

Anyway Bernard I agree that Opats are a very good tyre & I have 4 x 265/70/16 for sale in the 'Market Place' if you are interested.

Cheers

[brett]

The reason for the 75 series tyres causing problems with the DID auto's is the gearing, the Auto DID has the tallest gearing of all models, I'm not sure why it is so high, compared to a landcruiser TD the pajero's gearing is much higher, in the manual the DID is doing just over 2000 rpm at 110K in 5th, the landcrusier which has more torque is doing over 2500 rpm.
The auto has a 5th ratio of .731 the manual is .76, the final drive for the auto is a tall 3.917, the manual is 4.1. then compare this to the petrol final drive of 4.3 you can see why the DID auto's have trouble with larger tyres.
As an example with 75 series the auto petrol is doing 2074 rpm but the DID is doing 1890 which is below the max torque figure for the engine. I notice a difference with the manual and 75 series tyres and I wouldn't want any taller gearing.

[bernardpotatoe]

Thanks for all your replies, I've gone safe and got Bridgstone Dueller D694's, 265/70-16. Now just have to get bush to see if the NP DID auto is anywhere near as fun as the NL Petrol Manual was (plus have to arrange bullbar for the winch, roof racks as my ARB full lengh is no good, new rack and fridge mount for the rear, suspension upgrade, the list goes on and on!).

[psproule]

Adam, the NCOP is still in draft and has not been ratified in any state. There is a bit more info from someone who went to the horses mouth here.

[kibz]

Is it possible to change diff ratios without side effect to the auto? i.e. run the manual DID diff ratio or petrol diff ratio.
Would this bring the torque ratings back into line with factory ratings of the motor/auto?

Cheers
Kibz

[mal&glo]

Hi bernardpotatoe

Future mods all sound great, pity your front axle mass will be over Mitsubishi max permitted of 1200kg by about 40-50kg before anyone gets in it - makes it unroadworthy, voids warranty, renders it uninsured. Probably will go 130kg or more over by the time a couple of full size people climb into the front seats when winch bar and winch fitted. (Mitsubishi's std. person apears to be 68kg)

Sorry about harping on about this mass/weight thing but will continue to do so until Mitsubishi sort things out and issue sensible mass figures.
Not picking on you specifically, just noted future mods and posting this to make you and anyone else aware of the ridiculous mass specs for NP DiD's

A lot of guys on this forum and others and seem to worry about the 15mm thing with tyre size but are unaware/oblivious/don't care about this other mass problem which is in my opion can lead to much more of a drama if things go wrong.

Mal

[nj swb]

Hi bernardpotatoe

Future mods all sound great, pity your front axle mass will be over Mitsubishi max permitted of 1200kg

Where did this number come from? Last I saw, the Gen 2 front axle was rated for 1600kg, the rear 1700kg. Are you saying the NP is lower?

The max GVM is typically limited primarily by suspension; what the springs can support, and the ability of the factory shock absorbers (tuned more for comfy ride than load carrying) to adequately control the laden vehicle. Hence bernardpotatoe's desire to upgrade his suspension along with the remainder of his modifications.

For an insurance company to deny a claim they need to prove that the accident could have been avoided had the "unroadworthiness" not been present. What's GVM for NP? 3000kg? Can an insurance company prove that the 3100kg GVM vehicle could have avoided the accident had it only weighed in at 3000kg?

I agree that most owners give no thought to GVM when they load their 4wd to the tips of their roof racks. But Mitsubishi owners are not the only ones in this category, and recreational 4wders are not the only guilty group.

[psproule]

Mal had his weighed against the front and rear maximum axle weights. Total GVM for an NP is 2850 or so KG. Slightly less for a 3.8L. Depending on the base model and the factory accessories it carries maximum payload can come down to 250kg or so - and that needs to include people!

Mal - your findings are one of the reasons I am putting a Smartbar on our new NP and am particularly weight concious when loading. I would also suggest perhaps that it is not just Pajeros that have this as a problem although I cant back that up with figures. I tried once but it seems that a lot of the detail at Redbook is actually wrong, and then the detail between my owners manual and the Mitsu website is different again. Three different sets of figures.

Pat

[pjchris]

Where did this number come from? Last I saw, the Gen 2 front axle was rated for 1600kg, the rear 1700kg. Are you saying the NP is lower?

The maximum front axle load for a Gen 3 (NM/NP) is listed in the manual as 1200kg.

Peter

[marquis]

Hello All,
I have just upgraded from a 99 NL manual petrol to NP DID auto. I had 265/75-16 Toyo OPAT AT's on the NL and found them very good. The spare of the NL is still new and I have it. I was going to purchase 4 more the same to fit on NP (was a Toorak tractor with HT's (bald)), but have read somewhere about the torque converter lock up having issues with the larger diameter tyres. My brother has a petrol NM auto with 265/75-16's and seems to have no issues.
Thanks in advance
Bernard

Bernard,

I have the DiD Auto NP and yes the torque convertor does not lock in 5th for long (ie it locks - speed decreases slowly from 100kph to 97kph then unlocks). If you drive in 5th unlocked it will burn the auto fluid in the tranny. I drive in 4th and the auto has no problems locking the TC contin. even up most hills.

To give you some idea what 265/75's are like - the vehicle feels like it is towing a trailer. Fuel ecom will drop from 9L/100km to 11.5L/100km (ie with loaded vehicle + roof rack - 12.8L/100km driving at 95kph).

Please note that at 10 to 80kph on bad tracks I obtain the same fuel ecom. (Just completed the Ficke River Track NT - wow good camping spots but the track is dodgy in places)

Next time I will look at 245/75? (about standard size) for my NP just so I can drive in top and have much better fuel ecom.

Cheers