OKA 413 _ A New Hope

19 Apr 2021 07:45 #81 by Alister McBride
Alister McBride replied the topic: OKA 413 _ A New Hope
Hi Deano, great job!

Wondering where you got a divorced 29 spline input shaft from? Usually they are 32? The 29 is a mated input usually...

Assuming you kept the angle of the 205 the same as the trans output and then matched the pinion angle to that also?

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  • Dean and Kaye Howells
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19 Apr 2021 11:29 #82 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 413 _ A New Hope
You're right on the money here Alister, actually 32 spline, my mistake. Ian Jones did the swap over and was busy with the digital angle gauge when fitting it. The wedges on the rear axle tilt the diff assembly to the correct angle. Depending on the vehicle the rear mounts may also need altering as well.

It wasn't a simple "out with the old and in with the new" upgrade, there was a fair bit of measuring involved with Ian working to a 1 degree tolerance (or better) to get the desired result. I'm glad I didn't have a go myself as there's no way I would have achieved the same result.

There is a marked improvement in drive-ability (available power) and decreased noise level with the NP205 as opposed to the old 'cloverleaf' HD150 transfer case. Cabin noise level is significantly decreased to the extent that I can now clearly hear air induction noise in the B pillar snorkel which will now need more sound deadening. :)

By far the most obvious improvement is the increase in available power, particularly when accelerating from low to mid engine revs in 4th or 5th gear. ie. at low engine power levels with little or no turbo boost, very noticeable and makes for easy/lazy driving/cruising. The ability to slowly accelerate from say 1000-1200 rpm or so in 5th gear after being too lazy to change down while driving through a small 'fly speck' town is greatly improved :)

Along with the NP205 a 'new' waste-gated HX35 turbo was fitted and a less aggressive factory Mopar viscous coupling and 37" AT's on alloy rims which all contribute to a better driving experience.

The drive to Wompinni was the road test after the various changes were made and I was interested to check fuel consumption. On the way up I tried various rev/speed combinations to get a feel for the upgraded Oka and achieved 16.5 litres/100 Km over the 800Km's from Gippsland through Melbourne and up the Calder Hwy to the other side of Wentworth. Not a bad result considering. With existing wheels/diffs/gearing 1800 rpm is about 90-95 kph with 1950 rpm giving 100 kph. I gave the new turbo a bit of a try out on the hills which was maxing out at 29 lb. boost with the boot firmly planted. Certainly no problem holding 95-100 kph on hills (watching EGT's) if I wanted to. On the 'other tank' which included choofing about Wompini on Safari :) and home via Hattah Lakes NP and back down the Calder Hwy and through Melbourne to home and a return trip up the highway to the Yarragon weighbridge I did 1000.3 Km to the servo and refilled to the mark with 148 litres, so 14.8 litres/100 Km. Not bad :) :) :) This was sitting on my preferred cruising speed of 90-95 kph or around 1800 rpm.

Deano :)

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