131" wheelbase J20 under 119" J10

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j10builder
Posts: 92
Joined: Tue Mar 12, 2019 5:28 pm

131" wheelbase J20 under 119" J10

Post by j10builder »

I've got an 1981 J10, (119" wheel base) truck, with stock 4 speed manual etc. I also have wrecked, late 1980 model J20 (131" wheelbase) truck. My intention is to put the 4 speed manual w/granny (T18), transfer case and axles from the J20 under the J10 with a 4" lift kit (I'm open to suggestion for this as well). I know others have done this. I want to benefit fro your knowledge. What pitfalls should I avoid? Is there a particular lift kit that would make this easier? Do I need to move shackles or spring mounts on the axles? Any and all advice is appreciated. Thanks
'81' J10 w/all the good same year J20 stuff

XSapper
Posts: 148
Joined: Sat Jun 30, 2018 10:25 am
Location: Northeastern, KY

Re: 131" wheelbase J20 under 119" J10

Post by XSapper »

Swap out the steering box too.
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Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: 131" wheelbase J20 under 119" J10

Post by Cecil14 »

The only differences between the J-10 and J-20 will be springs, axles (brakes, etc.), transmission/t-case, and the steering box. Everything else is the same. You will likely need a different rear driveshaft, but you should be able to carry the front shaft over from the J-20. You could have the J-20 rear shaft cut down.

For lift kits, there's a ton of them available. What are your requirements? Do you want it to stay 3/4 ton rated? If so, none of the off-the-shelf kits are going to be for you, as they're all built around 1/2 ton spring rates. You'd have to go custom springs, if you want to keep the load rating. If you don't care, Skyjacker offers a kit that is well regarded. BJ's Offroad has another kit, Rusty's, Rough Country, Hell Creek, BDS, and others as well I imagine. I would personally avoid any kits with rear blocks, go with an all spring kit.


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank

Topic author
j10builder
Posts: 92
Joined: Tue Mar 12, 2019 5:28 pm

Re: 131" wheelbase J20 under 119" J10

Post by j10builder »

Thanks Xsapper and Cecil14 That's exactly the info I was looking for! If anything else comes to mind that I might need to do please let me know. A buddy of mine told me to keep gear ratio's in mind. I'm not sure what the final gearing on the J20 T18 and Dana 60 comes out to be but I assume that since they're from the same vehicle I ought to be able to keep up good highway speed?
'81' J10 w/all the good same year J20 stuff
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Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: 131" wheelbase J20 under 119" J10

Post by Cecil14 »

The J-20 probably has something around 3.73:1 gears. You can adjust your highway rpms a bit with tire size. If you want decent highway cruising, choose a little bit taller tire. Use this calc to compare:

http://www.grimmjeeper.com/gears.html


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank
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