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Discussion Starter · #1 ·
Been giving this a lot of thought and wondered has anyone looked into putting a modern 6 speed auto behind a 4.2td?
All the modern diesels run better with the auto due to quick shifts smaller gaps between gears.
I wonder which transmission would best suit the td42.
I think this could give a vehicle more performance gains than most engine mods.
 

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nissan
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I think this could give a vehicle more performance gains than most engine mods.
I'd say that about a 4 speed auto upgrade but I doubt that you will see much improvement with a 6 speed auto over a normal 4 speed. Where 6 speed autos really shine is with vehicles that have low air resistance and low road drag. The super low top gear revs can manage to keep the slippery vehicle rolling with not much throttle but I don't think that will be the case with a Patrol. Ask people with factory 6 speeds how they go while towing and they will tell you that the higher gears never get used because there is too much load for the engine to be comfortable at such low revs. I expect it will be the same in a loaded Patrol that weighs about the same as a Falcon with 1.5t camper trailer.
 

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Discussion Starter · #4 ·
I can see the towing would need to keep lower gear but I recently drove from sydney to adelaide and wished for another gear the whole trip.
Because a auto changes quicker and seamless you don't spend all that time between gears changing up or down.
I can't get across a set of lights without changing to 2nd.
 

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I'm not familiar with the Ford boxes but that ZF looks like it would be suitable. My 6 speed auto experience is limited to a Commodore SS with a 6L80
no doubt anything could be adapted if you have the dollars.
wasnt there a guy trying to put either a zf or 6l80 behind a zd a year or so ago?
quite a lot of the barra turbo guys are doing the zf6 speed and love it. same low rpm top gear but a much better spread below it.

OP
imo, spending potentially 20+k to put a 'fancy' auto behind a td is a little bit silly.. Would it be nice? sure. logical, not really.
re4 it (5k ish) and spend some dollars on power upgardes if you want to go a bit quicker.
 
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nissan
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Because a auto changes quicker and seamless you don't spend all that time between gears changing up or down.
I can't get across a set of lights without changing to 2nd.
I have no criticism about you wanting the auto but as simcoe points out, the benefits of a 6 speed over a 4 speed are not going to outweigh the costs.
 

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Marks Adaptors puts the GM 6L80 into manual landcruisers. I wonder they are quicker or more economical. The standalone controller PCS TCM 2650 they use is meant to require a mountain of work to get it tuned because the 6L80 is mechatronic.

A Ford 6R80 is not mechatronic and is meant to be relatively easy to tune with the “Quick 6” TCM.
 

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I can see the towing would need to keep lower gear but I recently drove from sydney to adelaide and wished for another gear the whole trip.
Because a auto changes quicker and seamless you don't spend all that time between gears changing up or down.
I can't get across a set of lights without changing to 2nd.
Unless you are fully loaded or on an incline you should be able to start off in 2nd. I have pulled a 28ft van and started off in 2nd on the flat.
 

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Discussion Starter · #11 ·
Yes i can do that as well but what rpm are you doing at 110kmh? My truck is doing 3000rpm. A vehicle with a 6 speed auto would be doing 1600rpm. Big difference on fuel
Marks Adaptors puts the GM 6L80 into manual landcruisers. I wonder they are quicker or more economical. The standalone controller PCS TCM 2650 they use is meant to require a mountain of work to get it tuned because the 6L80 is mechatronic.

A Ford 6R80 is not mechatronic and is meant to be relatively easy to tune with the “Quick 6” TCM.
That sounds like it would work. Even a auto out of the landcruiser would be a good option. My mates does 1500rpm at 100kph.
 

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CRD Wagon
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Yes i can do that as well but what rpm are you doing at 110kmh? My truck is doing 3000rpm. A vehicle with a 6 speed auto would be doing 1600rpm. Big difference on fuel

That sounds like it would work. Even a auto out of the landcruiser would be a good option. My mates does 1500rpm at 100kph.
RE4 ZD with 285s seems to spin about 2K at 100. Dunno about the TD but ZD is lugging and IMO not in a good way at those revs at 100.
 

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GQ Dual Cab. TD42Ti with fruit.
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First thing is, a TD42 at less than 2000rpm is not good, even if you have 750nm and 200RWKW. At 100kmh your EGT's are higher than if you were at higher revs. Higher EGT's indicate more fuel usage, not less. Personal experience here, not heresay. I can do back to back runs between 4th gear and my overdrive 5th in my manual, and the results are the same every time. With a load on or up hills etc it is even worse. Incidentally, my overdrive 5th gear is the same ratio as the Jatco 4 speed auto.

However, I think a nice auto behind your TD42 would be great!!!! I am slowly working towards installing an RE5 Jatco, the 5 speed tiptronic box found in the 4.8 Patrol.
 

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I agree the auto is a good idea but not the 6 speed for the reasons given. 1600 rpm sounds like a good idea but if that is not anywhere near peak torque then i won't be the fuel benefit you think. My understanding is that the most efficient cruising rpm is near peak torque. I had a 6 speed manual LS1 Commodore and sure it was OK in top cruising on the flat on the highway but you still needed to change down as soon as there was any load. I imagine a 6 speed auto in a TD towing will be a complete waste of a couple of gears most of the time.
 

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GQ Dual Cab. TD42Ti with fruit.
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Yep, and it's not only to do with the turbo either. Your injector pump is driven by the crank, and at lower engine revs, you also have lower pump revs. It is most efficient above 2000rpm. Oldmav tells me that 2200-2400 is ideal.
 

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RE4 ZD with 285s seems to spin about 2K at 100. Dunno about the TD but ZD is lugging and IMO not in a good way at those revs at 100.
I have a 42 with RE4 and 285s, about 2100 I think at about 100 clicks, pretty much perfect I reckon, drives beautifully at that level, but wouldn't want any less revs I think so not sure about going back to 35s.


Yes i can do that as well but what rpm are you doing at 110kmh? My truck is doing 3000rpm.
Holy crap! Try taking it out of second gear, should help :)
 

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I have a 42 with RE4 and 285s, about 2100 I think at about 100 clicks, pretty much perfect I reckon, drives beautifully at that level, but wouldn't want any less revs I think so not sure about going back to 35s.
Same here. 2050 rpm with 285s and 4.3 diffs and TCC locked. EGTs are around the same temp as they were with the manual box at 2250rpm cruising at 100kmh. Hit a hill the TCC unlocks and the revs come up where you want them. I dont think you can compare the manual box that has no slip in the clutch, to an auto with a torque converter that has slip until the TCC locks. The recommendation on my heavy duty torque converter is no more than %50 throttle when the TCC is locked.
 

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Every dog has his day
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I leave mine locked on slight hills, and I probably go 75% throttle at a guess.

The mob whole built my converter do a triple plate lock up that's good for over 1000nm, if I have to take box or engine out for any unrelated reason at some point I'll get that done.
 
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I leave mine locked on slight hills, and I probably go 75% throttle at a guess.

The mob whole built my converter do a triple plate lock up that's good for over 1000nm, if I have to take box or engine out for any unrelated reason at some point I'll get that done.
Do you know what the standard lockup clutch is good for?
 

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Every dog has his day
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Do you know what the standard lockup clutch is good for?
Not sure but I’ve been told it’s good for more than you’d think provided you’re gentle on throttle and don’t just stand on it suddenly. If I get time this week I’ve been planning to pop in to see the bloke who built it as he’s a bit if a legend with them and ask the question
 
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