Looking for opinions on auto trans and engine upgrade for my OKA 4x4 . Its a little known truck made in Australia, more in the IVECO Daily, Mitsubishu Canter, Isuzu NPR truck category. Depending on model Gross weight is 5200 to 6000 KGS.
MIne came with the underpowered Perkins 4.0L Phaser 110T, best versions of this engine (intercooled) scrape out 130 HP and 300 FT LB.
Manual 5 Speed Spicer T5 transmission and a NP 205 Transfer case.
Dana 60 front and Dana 70 back axles, final ratio 4.88. 36 inch tires,
My plan is to install an auto, have secured a 4L85E from a 2008 GMC Duramx LBZ 3500 motorhome. Ultimately would look at an Cummins IS 4.5L common rail diesel for the engine , used a lot for Nissan Patrol engine upgrades, tuned up would be 330 HP and 660 FT LB . A few OKA owners put 4l80E trans in usually with a Cummins 6BT engine as well, and most of them didnt work out too well ended replacing with an Allison 1000 (way more expensive solution). One of the biggest problems seemed to be mainly with the torque converters, even with the 13.5 inch HD units HM-160/4461,
The 4l80s seemed to work out behind the low powered Perkins , needed decent trans oil cooling, some fitted 2 coolers. I know some of these 4L80s were built to Stage 3 specs. Behind the 6BTs, torque converters shredded the lockup clutches within 5000 kms, triple stack was better, but then also had oil leaks from the snub shafts cracking. Shredded lockup clutches contaminated the transmissions. Pretty sure stall speed on converters were 1800 to 2200. However the 6BT makes 660 FT LB at more like 2500 rpm plus.
Trying to figure out why these trans/converters failed so bad, vehicle weight is not far from a GMC 3500, final gearing close enough, bigger tires should of helped the situation. Have attached specs for 2008 GMC 3500 models with an LBZ engine, you can see the vans only were derated to 460 FT LB from 660 FT LB as they had the 4L85 fitted and the rest had an Allison 1000, my understanding is the Allison wouldnt fit in the van chassis. 4L85E specs are hard to find and define, but I have to assume mine is only rated for 460 FT LB and not the 660 FT LB the so called "superamatic" 4l85E has, so need to look at strengthening the box, from what I researched weakest links are the roller and sprag clutches, so maybe upgrade the roller clutch and the sprag to 34 element. Pretty sure my 4L85 has hardened input shaft and heavy duty clutches in addition to the 5 planetary gears. But the "supermatic" 4L85E also runs a modified valve body which from what I have read runs a higher line presuure, so maybe a Transgo HD2 would also work here for me.

To sum up what upgrades does the GM Performance "supermatic" 4L85E have that the factory supplied 4L85E doesnt ?




DURAMAX LBZ

DURAMAX 4L85E CONVERTER


ISB 4.5L DYNO





OKA 4X4 1996 XT MODEL

 

Welcome.

I'm certainly not an expert on your questions, although I have rebuilt a few 4L80e units in stock-ish form as a hobby.

I'm just subscribing for the content 👍

 

In 2008 were they still using an LBZ in Australia? It should be an LMM.

Sounds pretty sweet