Thread: Towing with the ZF4HP22

Thanks for the replies guys

OK, so towing in 4th/D is not a problem (ie:the box is up to it).

Those of you with oversize tyres are running bigger intercoolers and remaps. Those with std size (or close too ... 245/70) tyres running std tunes are doing OK .... towing more weight than me.

It seems my 265/70's with std tune just doesn't have enough oomph when shifting up to 4th due to the engine revs being just too low (need to try travelling at a bit higher speed before selecting 4th) ... the 6% extra tyre size beats me. MAF of late only shows a max reading under full boot of around 400 ... I have a new MAF to fit (believe the current one is the original with 180k kms on it). May improve things ?

I know it can do what I'm asking as I've towed a car float at about 2.25T several times (but on the prior 255/70 sized tyres being about 3.5% over), with std tune, and it coped well. Comfortable at 90 in 4th, 3rd lockup for hills ... able to hit 120km/hr with a little bit of effort on the flat open highway ... Won't do that at the moment.

I think in my current setup I've overdone it on the tyre size .... ???

Transmission cooler to go in in the next couple of weeks. Fit the new MAF and see how we progress from there ... don't want to do a remap until I can fix the broken exh' studs and fit a pyrometer ... that's a way off yet.

Also ... Is the oversized LT230 sump a worthwhile addition for towing my 1.5T camper ??

Thanks

Hi Kev
Just reading your post , with broken exhaust studs you may well be losing boost , also Maf reading low may be related , as you say , try new Maf, either way this seems more of an engine tune problem than a tyre size issue , 265/70 /16 shouldn't be a problem.

I think boost is ok at 1.28-1.32 bar on the nano when I give it the loud pedal.

Sent from my iPad using Braille

On the Pommy D2 forum I'm on they report lower TC temps towing large vans with the larger Transfer sump.
And Mattg, Tombies D2 wasn't exactly stock

Originally Posted by Fluids

Thanks. What size tyres ?

Sent from my iPad using Braille

255/65 on 16" rims.

I could travel faster, at least on big highways, but the advantage of having the box locked up in third rather than fourth is that 3rd is direct drive, and it places the least stress on the box. And I'm not keen to have the box reconditioned again while I own the car.

ok,, I'll ask,,

is direct drive in an auto a real thing?
or a hangover from manuals where the 5th gear used to hang off the end?

where is direct drive on an 8 speed?

[and Pinelli I understand about rebuild costs
]

I think the TD5 pulses kill more auto's than anything else(except lack of maintenance)

Ok, I'm no expert on gear boxes, manual or auto, but the gear ratio in 3rd is 1:1 (if you trust Wikipedia )


This animation from youtube [ame="https://www.youtube.com/watch?v=Y1zbE21Pzl0"]youtube animation[/ame] shows 3rd with lots of locked gears, so pretty much a direct drive.

I reckon that the torque converter is more likely to be locked up more often if you drive in 3rd rather than D, so that if nothing else will save damage to the box.

where is direct drive on an 8 speed?

AFAIK 8 speed transmissions are not really 8 speed, but combine 2 or more gear sets to get the 8 speeds, which has only been possible since computerization. eg 4 may be 1plus 2.
If you can find the combinations of gears that give the 8 speeds then you may be able to find out.
Regards Philip A