Amigo differential question

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rat76
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Joined: Sat Jun 02, 2018 8:44 pm
Location: NE Oklahoma
Isuzu vehicle(s): '87 P'up 2.3 L, auto, Webber carb, Trooper rear axle, ex class C motorhome

Amigo differential question

Post by rat76 »

I'm researching a differential swap. I've got a '90 Trooper rear axle in my Pup & would like to replace the 4.56 gears with 4.3, I notice that Amigo 12 bolt carrier assemblies have an extra gear attached to the ring gear and what looks like a speedo drive on the front of the carrier.

What is this & will it affect the fit of a '92 Amigo Carrier assembly in my Trooper axle assembly.

Thanks in advance
Jim
oldestisuzuist
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Re: Amigo differential question

Post by oldestisuzuist »

That's probably a ABS tone ring & the ABS sensor you're looking at. As long as the added parts don't make the assembly too large to physically fit into the Trooper axle housing (and I don't think they will) the Amigo 3rd should work in the Trooper axle, the rear ABS just won't function.
The downside is that's a lot of money for very little gear change, a 2" larger rear tire diameter will give the same effective final drive as 4.30 gears. Unless the Amigo also offered something like LSD I couldn't justify the change.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.
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rat76
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Posts: 21
Joined: Sat Jun 02, 2018 8:44 pm
Location: NE Oklahoma
Isuzu vehicle(s): '87 P'up 2.3 L, auto, Webber carb, Trooper rear axle, ex class C motorhome

Re: Amigo differential question

Post by rat76 »

There is one other factor. The cutest set of 14 inch dualls I ever did see. They don't make 14 inch tires big enough any more. :wink:

smokie dualls 1.jpg


DSCF2248.JPG


I'm going to wait til I get the 5 speed in & see what my highway speed is. I'm considering the 4.3 as I think I'd like a little lower gearing than the 4.1. If I can run a comfortable 65 with the 4.56 gears I've got I'll leave well enough alone.

Thanks for the info, ABS wasn't even on my radar. :lol:
oldestisuzuist
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Joined: Tue Oct 07, 2008 9:10 pm
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Re: Amigo differential question

Post by oldestisuzuist »

My Trooper has the same tranny OD & differential gear ratios but has 31-10.50x15 tires (actually 30.5" in diameter) & runs about 2800-2900rpms at 65mph. A 26" tire will turn at least 3250rpms at 65mph, probably a bit more because of the actual loaded radius. RPMs & MPH for a given gear ratio (tranny & differential combined) change between 3% & 4% for each 1" change in tire diameter, so you can get a good idea of your highway rpms for whatever tire diameter you are actually running, then decide if you really need a gear ratio reduction. My point is the difference between 4.56 & 4.30 gears is probably not cost effective since the 4.30 gears will only lower the rpms about 200 at 65mph. A more cost effective method might be increasing tire diameter since tires eventually have to be replaced anyway. You can still get 14" tires up to 27" in diameter if this is enough change from your current tire size.
One other bit of news- the speedo drive gear inside your new manual tranny is sized for 4.10 differential gears & a particular size tire, so your speedo reading will most likely be off with the 4.56 gears & what ever tire size you have. Before installing the tranny carefully pull out the speedo gear (don't break the aluminum bracket that bolts the cable into the tranny), read & record the numbers on the end of the nylon gear (these will be either a 5 or 6 gear pitch plus a 15 through 21 two-digit tooth count). To correct your speedo reading you will have to replace the tranny speedo gear with one that has the same pitch but the correct tooth count- provided one's available. Check the gear numbers in your auto tranny also, I think the gears & cables are interchangeable with the manual trannies. After determining how much your speedo is off post back all the info for help on getting the right gear to correct.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.
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