Outer Limits 4x4 Board

I've just taken this quote from the Chopped thread:

justinC wrote:Getting back to what Hardy said about lower first gearing and stall speeds, I got my 4HP22 converter stall reduced to 200rpm less than standard V8 RRC, and this will help a lot to keep it cool. Les Richmond automotive have done this aswell as the lower first gear ratio mod, ( I think using a BMW 5Series planetary set?) and have had good success I believe running behind big output V8's. I'm running a turbo intercooled Isuzu 4BD1 and this has already overheated and broken 2 ZF autos. This will be the third box, and I'm using a temp gauge on this one!!! I'm also going to detune it a bit.

JC, do you know why the ZF's broke? Was it mechanical or did it relate to the tranny running hot? What power/torque figures are you pushing through it? I'm wondering as I've had a power upgrade on the TD5, but am really unsure of the consequences on durability with the Zf22. An additional cooler has been fitted already to keep temps down as the light was coming on to regularly. Also where/how did you do the mods on the torque converter. In its current trim there is a big rev difference between unlocked while booting and locked.

Also keen to hear more about the lower first gear mod

I would say hey cooked a clutch pack or two - I had an illustrated article once on the common zf4hp22 failures - I will see if I can find it

Tom

dont know if this will help but I just broke my zf auto in my defender im running a 4.6v8 and the planetary gears shit it self. At the moment its getting rebuilt again (the box was rebuilt 12months ago) but this time Im using the planetary gears from a v12 jag and replacing all the clutch packs with heavy juty items and drilling out the oil wells to keep it cool. IM also putting a 30% 1st gear reducution in ,dont know the out come just yet hopefully this weekend can keep you posted if you like the guys that are doing the rebuild inform me that it will be difficult to break this one

Tom was right on the money. When I pulled it down, the clutch packs looked like they were from a well abused clutch from a dirt bike!!! There was a lot of discolouration etc. The rear planetary housing/ support was also cracked through, and the lock up clutch was trashed.

This box came from behind a grunty 4.6 John Davis stroker motor previously in the RR before the diesel conversion. It had its fair share of towing and offroad work etc, but the light never came on...I suspect that to produce an early up shift for the diesel engine, which put out a lot more torque than the 4.6 BTW, I had to play with valve spring pressures in the valve body, and I think I mucked up some where along the line, producing too much slippage and heat in the process.

I am now fitting a rebuilt box back in with a 200rpm less stall converter, from Manuel Automatics in Melbourne.(Thomastown, 03 94664499) and theoretically this should help with less slippage/ heat. I am also installing a temp gauge, and if necessary a bigger cooler if the box still needs it.

I think to some degree torsional vibration will be a problem, but this will be reduced as much as possible with careful idle speed adjustment. I hope.

The lower first gear mod was also done by these guys for Andrew at Les Richmond automotive, and seems to have been a hit with those who are using it .

I'll keep you all posted once it's back up and running again.
JC

So given that I'm in Lebanon and I need to modify my ZF, what parts would I need and where from? my mechanic has been on Rovers for 27 years, so he knows his stuff, but what parts, and where from? (I'm ordering the MD4.94L today, do they have anything to help out in the ZF department?)

Thanks as always guys...

I was under the impression that we're running the ZF 4HP22 which is rated to 380Nm, but the ZF 4HP24 which is fitted behind the 4.6V8 is rated to 500Nm, but is essentially the same transmission with a few different internal parts, including a bigger oil pump.

Are the differences in these known foir upgrades, or can the ZF 4HP24EH from the 4.6V8 be fitted to the TD5 in place of the 4HP22EH?

Slunn,

I think that the 4HP22 can be modded to the 4HP24 spec, and at the same time a different 1st gear ratio etc can be fitted. It requires a bit of case machining to fit the gear train etc in, but the whole change over is expensive anyway, so a small amount of machining is nothing.

Ask Andrew at Les Richmond what they did to some of his g'boxes, or talk to Manuel Automatics about strengthening your box. They are very helpful but very busy. Tony has been very patient with my incessant phone calls and enquiries while I worked out what to do with my ZF.

JC

No worries at all. Thanks for this JC.

So if i run a massive oil cooler that be enough to stop most of the breakage? can i damage a zf with not enough oil temp?

Andrew,

Yes, most trans destruction is from overheating, especially with 'small ' engines like rover V8's and Tdi's.

Structural failures and spragg clutch failures can also happen, but usually through abuse and/or high power and torque applications.

Got mine running tonight, now its time for a few valve body tweaks to get the shift points right.

JC