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rear end swap

M

mrmojo32

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LOUISIANA
I have an 89 GMC Jimmy with a 350/4 speed to 10 bolts front and rear. I am also running 35" tires. I am in Louisiana so all the off road is mud.

I am thinking about upgrading to a 14 or 12 bolt. I have 2 questions:

What gear ratio does everyone recommend?

If I went to a 12 or 14 bolt, what years would match mine? Also, are truck rear ends the same as for Blazer/Jimmy? I have never done an axle swap so I am wondering what will bolt up easily.

Thanks for any feedback in advance. :rolleyes:
 
wont comment on the rest as i still have my 10bolts but a 12 bolt isnt much of an upgrade. Go 14 bolt.
 
14 bolt all the way. 12 bolts are not really strong enough to make the swap worthwhile. any 3/4 ton 14 bolt from 73-87 will be almost bolt in, minus the conversion u-joint and new u-bolts. there are other years that fit I think but I dont know which ones.
 
ok

So truck axle assembley's of those years fit my '89 Gmc Jimmy... right?

Also any ideas on gear ratio with the set up I have and goign mostly mud?
 
Go with the 14b. The years listed will work. A ff from a 3/4 ton suburban or truck will be a direct bolt in, a 1 ton will require moving the spring perches. As for gears it depends on your tire size. If you stay with the 35's then 4.10 to 4.56 will work. If you plan to go bigger you will need lower gears. I run 39.5's with 4.10's for now, I am waiting to upgrade to a 5.13 ratio for some get up and go. Your front 10b will need to be changes out to an 8 lug setup or use a spacer/adapter for the rear to go with a 6 lug pattern.
 
what ratio are you running now? most of the stock 14 bolts I have seen in my area were 3.73, 4.10, or 4.56 ratios. 4.10 would probably be the best of both worlds if you are still driving it on the street since you do not have an overdrive. I know a lot of people will disagree with me but a 700R4 would be nice with 4.56 gears. that way you will have a really deep first gear(3.06:1) and overdrive to compensate for the 4.56. Look for a 3/4 truck and get both axles. the dana 44 is worth the proper bolt pattern alone.
 
I have 10 bolt now and I think it is 308. The transmission is a sm264 or something. It is a 3 speed standard with a L gear. The .350 motor has only slight modifications.

fall2006010.jpg
 
That's a nice lookin' truck man. I'd say go 14 bolt. I don't own one, but i do own a 12 bolt, and I hate it.
 
Rims

I wonder if I will be able to find those kind of rims in 8 lug pattern. I know the rear axle is shorter than the front so maybe an adapter would be better.
 
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