Max Power?

[Viggen]

Im pretty sure that Ashcroft builds a hybrid trans like this.

 

[rovertech]

I am not sure where you are getting this?

please link me to instances where people have toasted a 4hp22 from adding more power to the engine because I know of people that have bigger cams and headers and rimmer super chargers and such and have not had trans failures due to the increased power.

Auto trans fail from heat...keep them cool and they dont really fail that often. The torque convertor absorbs lots of the shock loads that would otherwise break components in a auto box. The TC takes those shock loads and slips and turns them into heat. So if you are adding more power and plan plan to use the trans hard look to increase the cooling of the unit and you then improve its ability to handle the increased power you are sending through it.

This isnt a rover thing its a car thing. ZF's are some of the best auto box's there are.

I have also had good luck with stronger clutches in the 22. I know Overfinch had had issues with finding a transmission to use for the SBC they were installing in the P38's. From what I understand the GM transmissions they were using didn't hold up as well as hoped and they reverted back to using the ZF. I may be wrong on that though. In either case I agree with Thom upgarde the clutches install a larger cooler and you should be good to go. I have installed modified 4.6's into trucks with standard 22's with no issues.

 

[R_Lefebvre]

Auto trans fail from heat...keep them cool and they dont really fail that often.

That's not the only failure mode.

Auto trans also fail when too much energy is dumped into the clutches on shifts. There are a number of factors affecting how much energy they have to absorb on a shift. Engine power is one of them, obviously. But also the speed of the shift. Trans are programmed with a certain time period built into the shifts, when the clutches are allowed to slip, in order to make shifts softer. This is another way that a bigger engine will destroy an auto trans. It can be fixed with higher energy clutches, which it sounds like that's what in the 4HP24. It can also be fixed by firming up the shifts. Less slip, less energy dumped into them.

Overheating the oil will make this situation worse, but overcooling it won't help if you're really overdoing it.

They also fail from even the smallest bit of water getting in.

ZF's are some of the best auto box's there are.

Pfft! From what I read when looking at repairing mine, the American auto trans repair industry does not share your enthusiasm.

http://www.transtec.com/rebuilder_news/3rd_q94r-n.pdf

Overall length is increased not the case length. The difference is in the bell housing to accommodate a larger torque converter. The oil pump and other internals are different but case length is unchanged.

Ok, I'll buy that. Sounds like the clutch diameter increased too, however? From the above link:

It sure surprises me that the “huge” - 3.94"
O.D. - friction will burn so easily. This friction is the main
thing ZF changed when they came up with their “heavy
duty” 4HP24. The frictions on that one are 4.92".
Apparently, the European Wizards finally realized that
they needed something bigger than motorcycle-sized
frictions to handle a 12-cylinder engine.