Thread: Isuzu and ZF

Originally Posted by bob h

Hi to all, thinking of changing the 3.5 out of my 88 rangie to a 4Bd1T and still keeping the 4 speed ZF box. Is this possible or is there a better option? Nothing wrong with the 3.5, just thinking of cheaper running costs long term.

Thanks Bob

Been there done that Bob, after lunching 3 ZF's behind mine I went to a 4spd LT95 manual. When it was going it was the bees knees, but let me down on a few occasions and that was that. The torsional vibration IMHO is too much for the clutch packs and at one point I completely stripped off the converter lock up clutch material. The ONLY way I would consider going back down that road is to use a 4HP24EH from a P38a and a compushift shift computer. At least these boxes have decent clutches and sprags factory, and the converter lock up clutch is way bigger friction area.

JC

Originally Posted by justinc

Been there done that Bob, after lunching 3 ZF's behind mine I went to a 4spd LT95 manual. When it was going it was the bees knees, but let me down on a few occasions and that was that. The torsional vibration IMHO is too much for the clutch packs and at one point I completely stripped off the converter lock up clutch material. The ONLY way I would consider going back down that road is to use a 4HP24EH from a P38a and a compushift shift computer. At least these boxes have decent clutches and sprags factory, and the converter lock up clutch is way bigger friction area.

JC

Thanks JC, I guess that a rethink is the go. What would be a good 5 speed and t/c combo? Bob

Originally Posted by bob h

Thanks JC, I guess that a rethink is the go. What would be a good 5 speed and t/c combo? Bob

If you are fitting a turboed Isuzu, then you should carefully think about trans options. Dougal and John (Bush65) are both running Isuzu boxes, but have found a few issues with the shifting arrangement etc but have overcome it eventually. There is little doubt the Isuzu box is the best option for outright strength and ratios, but is a little complicated.
I have gone for LT95 with .996:1 TF case ratios, Taper roller conversion to transfer case as per Military spec,(My G'box was ex 6x6 Perentie) and 33" tyres.
Apart from reverse gear which is very high, in fact I have to use low range when backing my trailer(A good idea anyway I reckon), I am happy with the ratios and fuel economy / highway performance. Offroad it still has good engine braking with the 33" tyres, and I have heaps of diff clearance, even though it would be better without the Salisbury diff in the rear.
I can cruise at 110km'h and get 15l/100 towing, or around 12l/100 without the camper on. I can get to the fuel governor on the flat in top gear, and still idle around in 4th at 50km'h all day.

I guess I am saying that I would either pick a LT95 or a Isuzu box, but the simplest solution is LT95 as a bellhousing change will allow easy fitment.
The LT85 Santana 5spd isn't as tough in 5th gear at all, I have seen a few fail with a torquey 4bd1T in front of them.

JC