J20 Steering Gearbox Questions

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The PIG Smith
Posts: 506
Joined: Sat Sep 03, 2011 10:54 pm
Location: Fort Wayne, Indiana

J20 Steering Gearbox Questions

Post by The PIG Smith »

Way back in the day, on my 1986 Grand Wagoneer, the power steering gearbox leaked like Niagara Falls around the pitman arm.
It was a lifted rig and I think at some point in time, the steering took a hit and the sector shaft was damnaged, causing the seal to be compromised.
From advice I was given over on the Mothership, I purchased a Chevy S10 powering steering gearbox.
I replaced the OE unit with the newer S10 unit.
The S10 unit had three mounting holes, but it had a quicker ratio that provided a better driving experience.

Now, on my 1986 J20, while driving, it seems like turning the steering wheel takes more turns than I think it should.
I feel like I driving a school bus.
I really don't know if this is normal operation or not.

From what I was able to research, the ratio of the J20 power steering gear box is 16:1
I do know that the J20 has a larger bore (worm gear) than the standard Wagoneer, Cherokee and J10. (3/4 ton vs 1/2 ton)

My questions are:
1. Should a good working J20 powering steering gearbox takes a lots turns of the wheel from lock to lock?
2. Is there a GM/Saginaw powering steering gearbox from a 3/4 ton/1 ton rig that would have a quicker ratio than the OE Jeep unit?
3. Is there a recommended aftermarket, 3/4 ton rated, quick(er) ratio power steering gear for the J20?
Bryan Smith
Fort Wayne, Indiana
2017 Jeep Grand Cherokee Limited
- 75th Anniversary Edition - 1941 Trim Package - Recon Green --Daily Driver
1986 Jeep J20
- Super clean rig from the AZ/CA state line -- Current Project
1982 Jeep J10
- Has become a Long Term Project.
1981 Jeep J20
- Commercial flat bed - Lost in a Divorce --gone
1987 Jeep J20 Pioneer
- Former Rick Bielec aka Ricbee plow rig. Major rust!! --gone

IFSJA Member #1933 Joined November 30, 2001
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Yeller
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Joined: Thu Apr 01, 2021 7:54 am
Location: Rogers County Oklahoma

Re: J20 Steering Gearbox Questions

Post by Yeller »

I'm with you, the 4 turn (16:1) box wears you out LOL

as for a direct replacement with the larger bore I'm not sure of any off hand without going to AGR or PSC who are getting new castings produced with the larger bore piston. Design wise, the only difference between a J10 and a J20 is the size of the piston inside the box, otherwise they are exactly the same. That being said, unless you are doing a lot of heavy hauling any of the later 3 bolt boxes will work, I seriously doubt you'll notice a difference. I know steering input wise my truck was the same feel going from stock tires to much larger/wider 33's, even off road never felt like I needed more, I wouldn't give a second thought to using the S10, Jeep YJ, XJ, ZJ or early TJ box, there are probably 100 other applications too, that box design was very popular in lots of vehicles from the mid 60's through early 2000's. Borgeson also makes new boxes to replace the earlier ones with a 12:1 ratio, just not sure they offer the larger bore. The popularity of that box is why the bigger power steering companies are able to purchase new castings with multiple piston sizes, which of course are always an option.
The bus I ride is so short it is a yellow Smart Car full of squirrels, monkeys and clowns.

1970 J2500 Resto Mod
https://www.fsjnetwork.com/forum/viewt ... 12&t=21395

1974 Bronco “Broncno”
https://classicbroncos.com/forums/threa ... st-3411909

sierrablue
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Re: J20 Steering Gearbox Questions

Post by sierrablue »

The ZJ box should be plenty strong--they put lots of 3/4 ton steering (pretty sure the box is, and the lower steering shaft DEFINITELY is, among other things) on those ZJs (and I have no idea why). It's a quick ~12:1 ratio box (< three turns lock to lock), and bolts right into the factory spot--and it's valved such that you get MUCH better feel; it gives the steering a much tighter, more modern feel. I believe the bolts are metric, and the hoses may be metric, but otherwise it's a bolt-in swap.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
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Yeller
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Re: J20 Steering Gearbox Questions

Post by Yeller »

sierrablue wrote: Sun Dec 18, 2022 8:42 am The ZJ box should be plenty strong--they put lots of 3/4 ton steering (pretty sure the box is, and the lower steering shaft DEFINITELY is, among other things) on those ZJs (and I have no idea why). It's a quick ~12:1 ratio box (< three turns lock to lock), and bolts right into the factory spot--and it's valved such that you get MUCH better feel; it gives the steering a much tighter, more modern feel. I believe the bolts are metric, and the hoses may be metric, but otherwise it's a bolt-in swap.
FYI: YJ, TJ, XJ, MJ and ZJ all use the same box.

Hit or miss on metric vs standard bolts, most are standard. They do have metric oring fittings, but there are adapters to get to inverted flare or JIC. I typically convert them with adapters to JIC.
The bus I ride is so short it is a yellow Smart Car full of squirrels, monkeys and clowns.

1970 J2500 Resto Mod
https://www.fsjnetwork.com/forum/viewt ... 12&t=21395

1974 Bronco “Broncno”
https://classicbroncos.com/forums/threa ... st-3411909

sierrablue
Posts: 1208
Joined: Wed Nov 30, 2022 8:02 pm
Location: MN/CO

Re: J20 Steering Gearbox Questions

Post by sierrablue »

What I've read indicates that the ZJ has a different box--could just be that the ZJs are all consistent though.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
User avatar

Yeller
Posts: 1521
Joined: Thu Apr 01, 2021 7:54 am
Location: Rogers County Oklahoma

Re: J20 Steering Gearbox Questions

Post by Yeller »

sierrablue wrote: Sun Dec 18, 2022 3:23 pm What I've read indicates that the ZJ has a different box--could just be that the ZJs are all consistent though.
Maybe, maybe not, they will all bolt in place of each other. Tire sizes were similar, axle size were the same, overall vehicle weights were similar so there’s little reason for them to be different, there are lots of things that can be manipulated within them to tune the steering feel but basic design is the same. Jeep used the same basic steering box from the Kaiser era through Chrysler era, there was no real steering changes until the early 2000’s.
The bus I ride is so short it is a yellow Smart Car full of squirrels, monkeys and clowns.

1970 J2500 Resto Mod
https://www.fsjnetwork.com/forum/viewt ... 12&t=21395

1974 Bronco “Broncno”
https://classicbroncos.com/forums/threa ... st-3411909

sierrablue
Posts: 1208
Joined: Wed Nov 30, 2022 8:02 pm
Location: MN/CO

Re: J20 Steering Gearbox Questions

Post by sierrablue »

That's not entirely true. The XJs have differently valved boxes, and the ZJs are valved differently from those. This changes the feel as you drive them. There's a reason the Firebird guys (who have Saginaw boxes) all want the ZJ boxes. Actually 2: feel and radius.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
User avatar

Yeller
Posts: 1521
Joined: Thu Apr 01, 2021 7:54 am
Location: Rogers County Oklahoma

Re: J20 Steering Gearbox Questions

Post by Yeller »

That’s the reason for maybe yes maybe no. I’ve built a lot of steering boxes and mixed and matched a lot of valving, changed ratios and refit the tolerances on the rack, ect. yes there are some differences, but at the end of the day they are the same basic design. For example if you feel the steering is too stiff or heavy you can change the shuttle valve for one with a lighter torsion bar to lighten the steering feel, same if it is too soft. There are 1000’s of combinations possible and never change the housing. From my digging in the past except for a few low volume specialty vehicles they all turn the sector shaft the same number of degrees so to increase steering angle you need to change pitman arm and steering arm ratio, not just change the box. Having built 100’s of steering systems on solid steer axles from scratch changing the pitman arm/steering arm ratio is the only way to change the steering angle of the tire.

The steering ratio is determined by the rack screw. Variable ratio or constant ratio comes from the rack piston and sector shaft. Steering feel is determined by the shuttle valve torsion bar. Over all steering power come from the size of the rack piston and pump pressure. For instance, you want softer, over boosted feel, use a Cadillac shuttle valve, same with more overall power, Cadillac pumps make the most pressure. Still need more power and/or off road a lot, tap the left and right pressure circuits and add a steering ram. Like I said, 1000’s of combinations to get what you want.
The bus I ride is so short it is a yellow Smart Car full of squirrels, monkeys and clowns.

1970 J2500 Resto Mod
https://www.fsjnetwork.com/forum/viewt ... 12&t=21395

1974 Bronco “Broncno”
https://classicbroncos.com/forums/threa ... st-3411909

dyermullet
Posts: 84
Joined: Fri Mar 04, 2022 10:54 pm
Location: Texas

Re: J20 Steering Gearbox Questions

Post by dyermullet »

Yeller wrote: Sun Dec 18, 2022 7:56 pm That’s the reason for maybe yes maybe no. I’ve built a lot of steering boxes and mixed and matched a lot of valving, changed ratios and refit the tolerances on the rack, ect. yes there are some differences, but at the end of the day they are the same basic design. For example if you feel the steering is too stiff or heavy you can change the shuttle valve for one with a lighter torsion bar to lighten the steering feel, same if it is too soft. There are 1000’s of combinations possible and never change the housing. From my digging in the past except for a few low volume specialty vehicles they all turn the sector shaft the same number of degrees so to increase steering angle you need to change pitman arm and steering arm ratio, not just change the box. Having built 100’s of steering systems on solid steer axles from scratch changing the pitman arm/steering arm ratio is the only way to change the steering angle of the tire.

The steering ratio is determined by the rack screw. Variable ratio or constant ratio comes from the rack piston and sector shaft. Steering feel is determined by the shuttle valve torsion bar. Over all steering power come from the size of the rack piston and pump pressure. For instance, you want softer, over boosted feel, use a Cadillac shuttle valve, same with more overall power, Cadillac pumps make the most pressure. Still need more power and/or off road a lot, tap the left and right pressure circuits and add a steering ram. Like I said, 1000’s of combinations to get what you want.
Yeller, you should do a writeup on this. I have had the boxes apart to replace gaskets but never swapped parts.
83 J10
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