J20 tech questions

[superdave]

I'm trying to sort out some questions on my 77 J20 parts truck and how some of the parts compare to my 77 Wagoneer.

First is the steering gear box- I've seen some use the J20 box as an upgrade- is it just for the different gear ratio (more turns lock to lock), making it easier to turn big tires, or is it a bigger stronger box?

Front axle- the J20 has a higher capacity rating. It has bigger breaks and its 8 lug, but what about it earns the higher rating? Stronger shafts? Tubes?

Suspension- did the J20 use the exact same springs as the waggys or were they stiffer for increase payload? I have no idea if what I've got is stock, but the distance between frame and axle is a little higher on my J20. Also, take a look at these rear blocks. Factory? Also including a pic of the truck for reference. Not sure if anyone can tell if it looks stock height with no bed and cut fenders...

Thanks for any help.

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[Cecil14]

Compare the piston relief on the steering boxes, the J20 box (if it's still stock) has an enormous piston which gives it a lot more assist. I had one, I swapped to an S10 box and will not be going back. If you're running giant tires and trying to turn on high traction surfaces, the J20 box may be for you. If you want road manners, the S10 box wins hands down.



This is why the J20 front D44 is rated higher than the J10/wag/chero version. I can't remember where that pic came from, but it is not mine and I certainly can't claim credit for it. Great reference, though.

The J20 was a 3/4 truck, I believe the lowest GVW I've seen on those is ~6800lbs. For reference, J10s/wags/cheros were usually around the ~6200lbs mark. The J20 could be had in configurations up to 8400lbs GVW. Your vin will indicate which version your truck was from the factory. The blocks you have there are not stock, I don't believe blocks were ever stock on these. The J20 springs, even the softest ones, will likely rattle your teeth out in a wag, but they will have higher spring rates.


aa

[superdave]

Thanks Cecil. Cool pic of the axle tube cross sections. Makes a lot more sense now. I should have mentioned my J20 is an 8400 GVW.

[Cecil14]

The only difference I'm aware of between the different GVWs is the springs themselves. The front springs are the same dimensions between any vehicle of a given year, the rear springs will swap between long wheel base trucks of a given year as well (and many between years, but best to ask for confirmation there, a lot of weird changes at different points).


aa

[Stuka]

For '76+ J20's, the rear springs are the same dimensions as wag/cherokee/J10. However, '75 and older J-Trucks, they used different springs for short and long wheelbase. Short wheel base J-trucks, as well as wag/chero used 52" rear springs, and the long wheelbase J-trucks had 57" long springs. In '76, AMC switched everything to the longer 57" spring, but changed the mounts to the box mounts, instead of the post mounts.

J-Truck frames also get WAY wider than Chero/Wag frames. The front axle will bolt into a waggy, but the rear axle will need new spring perches. Also, you need a fair amount of lift to use the axles as they are much wider (About 8.5" wider in back, and 5" wider in front)

[superdave]

Thanks for the info guys. This thing is pretty cool.

[XSapper]

You are going to end up building a J20.

[1979bettywhite]

You are going to end up building a J20.

[superdave]

You are going to end up building a J20.

Lol can't get nuthin past you guys

[XSapper]

You are going to end up building a J20.

Lol can't get nuthin past you guys

I know what it's like for the parts vehicle to become the next project.
The J20 I am working on had a dump bed on it. It had been removed and replaced with a wooden flatbed. a lot of work ahead on it. I think you should find or make a dump to put back on it and fix it up.

[superdave]

You are going to end up building a J20.

Lol can't get nuthin past you guys

I know what it's like for the parts vehicle to become the next project.
The J20 I am working on had a dump bed on it. It had been removed and replaced with a wooden flatbed. a lot of work ahead on it. I think you should find or make a dump to put back on it and fix it up.

Ya know, I never realized I needed a dump truck until I parked one in my driveway. Who needs mulch?! I'll drive! We'll see, I told my wife her Christmas present would be getting it out of the driveway.

[XSapper]

Lol can't get nuthin past you guys

I know what it's like for the parts vehicle to become the next project.
The J20 I am working on had a dump bed on it. It had been removed and replaced with a wooden flatbed. a lot of work ahead on it. I think you should find or make a dump to put back on it and fix it up.

Ya know, I never realized I needed a dump truck until I parked one in my driveway. Who needs mulch?! I'll drive! We'll see, I told my wife her Christmas present would be getting it out of the driveway.

A little bit of prep work, cheap home brew paintjob, patch the floorboards and then park in the backyard while you find or make a new bed for it. You told her you would get it out of the driveway, not get rid of it!

BTW whoever trimmed the fender flares did a pretty good job, it looks way better than the ones that remove them.

[superdave]

Haha I just need to find someone else with that same attitude

[XSapper]

Haha I just need to find someone else with that same attitude

Good luck finding a member of the opposite sex that will go along with things us guys like to do.

[superdave]

I'm content with a wife that allows it, she doesn't have to go along with it.

[fsj454]

J20 front dana widetrac 44 8 lug has the thickest axle tube size available . If you want to custom cut a axle housing .. If you cut a NT 44 thin tube to fit a cj you cut one side .If you take a widetrac dana 44 j20 8 lugger bigger tubes you have to cut each side to fit twice the work but 10 times beater. I use dana HD60s in all my custom builds . But j20 front 44 widetracs 8 lug are VERY STRONG HOUSINGS . I am hording one in my piles for future billed .