Author Topic: Converting From Isostatic back to Gear Lever Arm  (Read 4073 times)

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brook308

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Converting From Isostatic back to Gear Lever Arm
« on: August 12, 2014, 06:10:34 PM »
Hi All,

Just thought I post this for those of you who are converting from Iso Static shift to the old lever arm.
I have done this on twinspark 75 transaxels a few times with no problems but I have now found one retro fit conversion that did give me some grief.

I have converted my sons 85 GTV6 from it's standard open diff 4:1 Isostatic transaxel to a transaxel from a 75 3.0L Potenziata. The Potenziata gearbox is the same as any 3.0L 75 gearbox except it's final drive is 3.72:1 vs 3.5:1.

The gotcha is when you convert from Isostatic to non isostatic the gear selector lever arm and shift rod do not clear the rear v6 doughnut.

It will clear a rear 2.0L doughnut ok but will not clear the 3.0L.

There is a way to make it fit but it involves moving the gear selector arm down a couple of splines and also cutting and welding the shift rod, and you also have to grind some material from the gearbox shift arm so you can still get 5th gear.


Jekyll and Hyde

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #1 on: August 12, 2014, 07:01:39 PM »
The non isostatic version in the early GTV6 has less offset on the cast elbow (part with splines on gearbox) than the 4 cylinder, and a different rod between there and the bottom of the gear lever.  Not an easy thing to find though, given there weren't that many GTV6s without isostatic, and GTV6s don't often tend to get wrecked.
« Last Edit: August 12, 2014, 07:09:03 PM by Jekyll and Hyde »

brook308

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #2 on: August 15, 2014, 08:58:55 PM »
The non isostatic version in the early GTV6 has less offset on the cast elbow (part with splines on gearbox) than the 4 cylinder, and a different rod between there and the bottom of the gear lever.  Not an easy thing to find though, given there weren't that many GTV6s without isostatic, and GTV6s don't often tend to get wrecked.

Yes that would be the way to do it.
I have managed to modify the cast elbow, a two litre shift linkage and a isostatic gear lever but it was lot of mucking around to get a good change.

jazig.k

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #3 on: August 15, 2014, 11:15:26 PM »
What's the benefit in going back? No rebuilding worn out parts to trying to find NLA ball joints? Been 8 years since I drove a non-iso gear shifter so I don't remember any feel change.
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Mick A

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #4 on: August 16, 2014, 08:00:26 AM »
I think it's more a personal preference thing rather than a "this is better" or "that is better" thing.

LaStregaNera

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #5 on: August 16, 2014, 08:26:52 AM »
When they were new the isos were great - 30 years on, and a rebushed non-iso is better than a flogged out iso, and a modified non-iso is even better...
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brook308

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Re: Converting From Isostatic back to Gear Lever Arm
« Reply #6 on: August 22, 2014, 06:02:10 AM »
What's the benefit in going back? No rebuilding worn out parts to trying to find NLA ball joints? Been 8 years since I drove a non-iso gear shifter so I don't remember any feel change.

We'll my sons Iso fell apart mid hilclimb so luckily there was an angle grinder at hand to get to the Iso from above. A cable tie fixed it temporarily and he never missed a run. But for racing purposes the non iso is the way to go, much simpler and less likely to fail.