4wd front caster

[dennislbrooks]

How much of a positive caster shim (if any) did GM add for the front Dana 44 /Corporate 10 bolt axle that has power steering?

I take the positive caster would reduce road wander if all else is ok also like on a straight axle.

Application could be a 75 K10 pickup. My application is a 88 blazer corporate 10 bolt under my 67 pickup.

[sweetk30]

guys tend to like min of 5*-5.5* and up in the mid 6* range if big tires .

caster helps the wheels go straight .

camber tips them sideways in/out .

toe points them in/out .

the last 2 eat tires if not set correctly .

and i have never seen factory shims in the front on the many many gm trucks i have had / scrapped / worked on in over 20 years .

[57taskforce]

Normally the caster really starts to come into play when you lift it. On higher lifts It can turn into a compromise of caster vs. pinion angle. In stock applications the caster built into the axle should be sufficient. I had a Lift on my Grand Cherokee for a little while. I was always battling caster and pinion angle to keep it drivable and have death wobble or bad vibrations. These leaf spring trucks don’t seem to have near the issues with these things that the Jeeps do. As said above a good median target is 5.5* or so.

[Mike C]

I've taken apart the front suspension on three different factory power steering equiped 4x4 trucks and none of them had any sort of shims. All caster built into the axle and same for manual and power trucks.

[dennislbrooks]

I found this article that supports all your post advice above. It descibes front 4wd straight axle dodges but should relate.

https://www.thurenfabrication.com/te...-handling.html

I do have a slight toe-in that I will put back to straight - zero. My truck drives very well. I just want it to be a little better and I do take it on long truck show trips.

I also brought this up because I have a thread in 47-59 where I just added power steering to my 59 GMC Fleet 2wd straight axle and added a 6 degree shim. I removed the factory 2 degree shim. I see now that it relates little to a 4wd straight axle. Since I put power steering on the 59, making the leap to a 4wd is not as great. Change my pitman arm sector shaft to a 4wd shaft and use the 4wd pitman arm. Not sure on draglink length yet. I have a 12 bolt already in the 59 rear - 3.73 and I have a very good NP208 in hand. I have a rebuildable 4wd 700R4. My Dana 44 front in waiting just at the moment has the wrong gearing - 3.07.

[57taskforce]

Just an FYI 0 toe isn’t the best place to set it. I would opt for 1/16th inch toe in. This will provide you with more stability and predictable handling.

[1976gmc20]

Originally Posted by 57taskforce

Just an FYI 0 toe isn’t the best place to set it. I would opt for 1/16th inch toe in. This will provide you with more stability and predictable handling.

I was thinking the spec was something like 1/4" ......?

[dennislbrooks]

I thot it was 1/8" toe in however some rod builders (not necessarily 4wds) around here say they set the toe slightly out and road wander disappears. May be a little harder on tires.

Dunno

[61K10]

Somebody posted this don't know if its correct.

4x4 caster from factory

63-68 3* 60-62 missing? I put a 4* shims on my 61 44 with power steering. need to reset the toe to 0 as in the post above.

69-76 4*

77-91 8*

[57taskforce]

1/4” is about the most I’d ever go. I’ve run 3-4 of them at 1/16 and been happy with the way they drive. I guess it’s my personal preference. Ive never really had any issues with drivability/wandering on stock height trucks.

[dennislbrooks]

Argh...

According to my 71-78 Chiltons Truck and Van Repair book, road wander can be blamed on 4 things:

Caster ---- 2wd should be positive (corrected) ( only G series vans were about 0 as well as about 0 camber) and close to 6 degrees and even for both sides - different for 4wd

Uneven tire pressure or treads

Worn or damaged suspension components

Damaged power steering gear.


Toe-in is required because of camber. Generally if camber is 0 the toe-in is 0. The purpose of camber is to take some of the load off the outside wheel bearing.

A 71-78 K10/20 is caster 1.5 degrees positive ( no adjustment), camber is 4 degree positive ( no adjustment), toe-in is 1/8 to 1/4 inch., spindle inclination is 8.5 degrees.

Positive caster makes the truck want to steer downhill on a crowned road and steer in the direction of a crosswind.

[Richard]

Originally Posted by dennislbrooks

Argh...

According to my 71-78 Chiltons Truck and Van Repair book, road wander can be blamed on 4 things:

Caster ---- 2wd should be negative and close to 6 degrees and even for both sides - not the case for 4wd

Uneven tire pressure or treads

Worn or damaged suspension components

Damaged power steering gear.


Toe-in is required because of camber. Generally if camber is 0 the toe-in is 0. The purpose of camber is to take some of the load off the outside wheel bearing.

A 71-78 K10/20 is caster 1.5 degrees positive ( no adjustment), camber is 4 degree positive ( no adjsutment), toe-in is 1/8 to 1/4 inch., spindle inclination is 8.5 degrees.

Positive caster makes the truck want to steer downhill on a crownwd road and steer in the direction of a crosswind.

Hmm... are you sure that is what is said in the book?
Not sure I have ever seen alignment specs on any car or truck that call for negative caster setting. A negative 6 degree setting would induce shopping cart type handling. From what I have seen the factory caster setting on solid axle K series is +4 to +8 degrees. More positive caster also introduces negative camber as you turn allowing outside tire to contact road with vehicle weight shift. Wanted to add camber is usually 0 + or - 1 degree, seeing as axle is solid. Any more would cause damage to axle shaft.

[dennislbrooks]

Agree Richard on negative--only slightly on vans if at all. I will correct above and say corrected. Sorry about blurred.


So should I add 4 degree positive caster shims to my axle if only built-in 1.5 degree caster from factory?

[57taskforce]

I would measure the caster angle before I went to town adding shims honestly. That way you know exactly where your at. Not that that the manual is wrong but I’d rather verify first.

[Richard]

Agree with 57taskforce. Have to know your starting point before going to town with shims. Camber is not adjustable. If it is way off axle is bent.
My recommendation, get a baseline from an alignment. Have them adjust toe so all is not lost. Jack up truck, support frame and hang axle to full droop. Disconnect front driveshaft at axle and let hang. If you can get +3 to +5 degrees positive caster without driveshaft bind you should be good. I did get away with clearancing the cv on my 72 3/4 ton a small amount to avoid bind when I had 8" lift front springs on it. While not ideal I ran about 1 degree positive caster using shims on it to avoid cutting and rotating knuckles. On my current build I will shoot for about +8 degrees on my 4 link. Allowing adjustment from +6 to +10.

[dennislbrooks]

I have no lift on my truck. I run negative arch on the front with no lift block. I have a picture of a 67 chevy brochure of a 1/2 ton 4wd. I could not get mine as low as the pic.

The avatar is correct. My 67 year old wife can get into the truck with no step. Yea she still complains.

Does the negtive arch change the caster? Pic is full weighted drop.

Also below (Autozone Repair Guide) is another alignment spec for chevy trucks. Looks like the Chiltons may have caster and camber backwards.

[Richard]

Like I thought, 4-8 degrees. Should be no problem adding caster shims with no lift. As said you still need a starting point. So get an alignment. If only 1.5 degrees or so add a 3 degree shim. Always ran 0 on toe myself for straight axle. On my 72 3/4 ton, 85 1/2 ton and my current 72 1/2 ton.

[Richard]

Wanted to ask. What is the intended purpose of the overload shocks on the front axle. Do you haul a lot of weight in the truck?

[dennislbrooks]

I added them when I changed from a sbc to the BBC. I supposed I could have put in another leaf (this would have effected my negative arch) but the overload shocks which I put the top reinforcement plate on seem to work well with the negative arch.

I also used them as maybe another safety point. My thinking if I broke a main negative leaf it would come down on the stop with the sway bar, leaf attachment, and steering helping hold it in place and the overload assisting in maybe holding it up a little until you can stop.


My axle being a 1988 Blazer which is very likely same 8 degree caster as a 1987 pickup, should have 8 degree caster built in. I did have it aligned but I may need a more informed alignment shop. You may have seen Bethel, Ohio on the national news. That is where probably the best shop around here is to take it to. The truck drives well, It just does not act like my 2006 or 2015 4wds do. May never - dunno.

I have a 2 degree shim I could add for testing.

Thanks for you guys help. It did expand my knowlege on this issue.

[57taskforce]

In my opinion, that comparison is Apple to oranges, the new ifs trucks ride so much more smooth and have very nice road manners. The old solid axles are stronger than the ifs stuff but the trade off is they won’t ever drive quite as good as the ifs stuff does. Even the ford and doges of today don’t behave the same as the gm stuff does on pavement. That’s not to say that you can’t get the solid axle to behave well but it’s not gonna be the same driving experience that the newer stuff is.

[dennislbrooks]

57, Richard - after all my rambling -- the problem appears to be the Toe. I have a lift so I measured the toe as accurately as I could and I consistently got a toe-out reading of 1/2 inch. I adjusted to 1/4 toe-in as to get 1/8 the adjusting coupler slot did not point down as I like.

I took it for a test drive and dang --- what a diffence on wander. I will watch tire wear and adjust if a problem.

I do need to slightly straighten the steering wheel with the draglink now.

57, I agree on the ifs.. This truck now is as fun to drive as my 86 toyota 4wd with a sbc that I used to have.

8-)

[57taskforce]

Awesome! That much toe out probably did make for a handful! Glad you got it figured out. I know some don’t like the “over” assisted 69-72 4x4 Steering feel. I personally enjoy the way my K20 drives, its a different feel than my new trucks but it’s still a pleasure to drive.

[Richard]

Glad you got it figured out!