Builds The Clustertruck Rides Again - Refurbishing a 1975 Chevota (1 Viewer)

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I’m thinking you’re likely on the right path on the pitman arm length being “less than ideal”.

Yeah, I'm just curious as to how much the extra quarter inch before I run out of steering stop would really improve things or if it would be a largely unnoticeable gain.
 
check out the pitman arm for a 98 grand cherokee, longer, beefier, has a nice drop to it.
 
check out the pitman arm for a 98 grand cherokee, longer, beefier, has a nice drop to it.

Google says that looks about right but I can’t actually find any dimensional information on it - length, taper, drop, etc.

Really with my very limited lift and extremely low steering box mount, I only need about 1-2” total drop on the arm to keep the drag link and tie rod parallel. Looks almost like the Cherokee arm might have a lot more drop than that. Naturally no auto part store near me seems to stock it but I’ll keep my eyes open.
 
If you measure the distance between the two steering stops I can tell you easily.

Mike

As in the steering stop on the front of the knuckle and the one on the back? If so, it's roughly 7.6 inches.
 
OK so I'm going to make a bunch of assumptions here just to get us an idea. So it looks like a 0.25* movement in the stop on rear of the knuckle the inside tire is going to get you ~1.9* more steering angle on that side.

Now Ill just assume you get 27.1* on the inside tire now with 95% Ackermann:
1603850727710.png


And with that extra bit ~29.0*:
1603850839559.png


Around 1.2' reduction in steering radius. That pretty significant!

If you want closer numbers I need more data, but I'm sure this is close enough.


Mike
 
OK so I'm going to make a bunch of assumptions here just to get us an idea. So it looks like a 0.25* movement in the stop on rear of the knuckle the inside tire is going to get you ~1.9* more steering angle on that side.

Now Ill just assume you get 27.1* on the inside tire now with 95% Ackermann:
View attachment 2479123

And with that extra bit ~29.0*:
View attachment 2479125

Around 1.2' reduction in steering radius. That pretty significant!

If you want closer numbers I need more data, but I'm sure this is close enough.


Mike
Mike,

Woh. Did you just have that spreadsheet laying around??

I’m not following what some of those measurements are so I’m not 100% sure how close you are on the numbers but it’s a cool theoretical at least!

Good to know a little adjustment goes a long way there.

Have any calculations laying around to determine how much angle is “too much” on a birfield while you’re at it?

I’ll look at this with a fresh set of eyes in the morning
 
We'll do ~26* before:
1603851661748.png


And 0.25 on the one side nets ~3.8* more angle:
1603851731171.png


So its actually a ~2.4' reduction in radius which is huge. Definitely noticeable.

You need to check your felts hitting the shank of the knuckle ball as well. I have RCV shafts/joints and they can handle a lot more angularity than the knuckle balls will allow.

As for the rest of the data I'm not sure what you have for these values:
1603852033053.png


Thanks,

Mike
 
I used to know what RCV rated their axles for angle-wise, but its been a while and I don't want to spread misinformation.

As for the OEM stuff I'm really not sure on that one. Hard to get your hands on that type of data.

Mike
 
Google says that looks about right but I can’t actually find any dimensional information on it - length, taper, drop, etc.

Really with my very limited lift and extremely low steering box mount, I only need about 1-2” total drop on the arm to keep the drag link and tie rod parallel. Looks almost like the Cherokee arm might have a lot more drop than that. Naturally no auto part store near me seems to stock it but I’ll keep my eyes open.
I use that arm on all my swaps. I buy straight from dealer. Not very expensive.
 
@Godfather90 - Not sure what we are talking about at "Kingpin Width" with a measurement like 44.5 I'm guessing the distance between the tie rod ends/steering arms, across the axle? In fact it's really just the "kingpin" terminology that's throwing me off, not sure what we're talking about there. I'm thinking it might actually be the center of the knuckle ball where the trunnions ride?

Also not clear on the distance offset tierod drilling measurement.

Wheelbase is only slightly extended from stock - 91.5, and I've move the rear axle rearward a touch.
Tires are 31's (but somewhere way down the road they will be 33's)
 
I use that arm on all my swaps. I buy straight from dealer. Not very expensive.

Aren't most of your trucks running 4" lifts though? Just wondering if I'd be over-correcting with 2" of lift. Sounds like it fits the box splines. Is there a particular drag link end you use on the other side? I believe my drag-link is right-hand threaded, 11/16-18? Looking on some jeep forums (after which I properly bleached my eyes) it seems like the XJ wranglers might have a similar arm with less drop, since those guys all seem to grab the ZJ grand Cherokee arms to fix the steering angle when they add lift. I definitely need to do more research/find one to measure.
 
We'll do ~26* before:
View attachment 2479146

And 0.25 on the one side nets ~3.8* more angle:
View attachment 2479147

So its actually a ~2.4' reduction in radius which is huge. Definitely noticeable.

You need to check your felts hitting the shank of the knuckle ball as well. I have RCV shafts/joints and they can handle a lot more angularity than the knuckle balls will allow.

As for the rest of the data I'm not sure what you have for these values:
View attachment 2479153

Thanks,

Mike

Ok so assuming the kingpin is essentially the rotational axis of the knuckle ball - some answers to above:

Kingpin width is actually very close. As quickly measured under the truck I got 45" from kingpin to kingpin across the axle, so that could easily be 44.5.
Wheelbase - let's call it 91"
Tie rod end to Kingpin measured to 7.5 just as you have it (FJ60 steering arm)
Tires are 31's

So the only measurement thats still a bit of a mystery to me is the "distance tie rod offset drilling" one. I'm guessing that's a measurement of the "bend" in the steering arm, and how far inboard the tie rod end is from the center point on the knuckle?
 
Ok so assuming the kingpin is essentially the rotational axis of the knuckle ball - some answers to above:

Kingpin width is actually very close. As quickly measured under the truck I got 45" from kingpin to kingpin across the axle, so that could easily be 44.5.
Wheelbase - let's call it 91"
Tie rod end to Kingpin measured to 7.5 just as you have it (FJ60 steering arm)
Tires are 31's

So the only measurement that's still a bit of a mystery to me is the "distance tie rod offset drilling" one. I'm guessing that's a measurement of the "bend" in the steering arm, and how far inboard the tie rod end is from the center point on the knuckle?


The distance I am referring to is the distance the tie rod riling is outboard of the king pin. If the steering is in front of the axle it is supposed to be outboard of the kingpin to create proper ackermann steering. If the steering is behind the axle it will be inboard of the kingpin axis.

45" sounds right for the lower kingpin bearing location. There is a ~9.5* steering axis inclination angle that puts the upper kingpin inboard of the lower.

The tire size should not matter in this case. Looks like the numbers are close enough on this one.

Thanks,

Mike
 
The distance I am referring to is the distance the tie rod riling is outboard of the king pin. If the steering is in front of the axle it is supposed to be outboard of the kingpin to create proper ackermann steering. If the steering is behind the axle it will be inboard of the kingpin axis.

45" sounds right for the lower kingpin bearing location. There is a ~9.5* steering axis inclination angle that puts the upper kingpin inboard of the lower.

The tire size should not matter in this case. Looks like the numbers are close enough on this one.

Thanks,

Mike

No, thank you! This is super interesting.
 
Aren't most of your trucks running 4" lifts though? Just wondering if I'd be over-correcting with 2" of lift. Sounds like it fits the box splines. Is there a particular drag link end you use on the other side? I believe my drag-link is right-hand threaded, 11/16-18? Looking on some jeep forums (after which I properly bleached my eyes) it seems like the XJ wranglers might have a similar arm with less drop, since those guys all seem to grab the ZJ grand Cherokee arms to fix the steering angle when they add lift. I definitely need to do more research/find one to measure.
stock, 2.5", 4" can all work. depends on how your box is mounted. ZJ grand cherokee arm is beefier than the rest and takes the same "jeep" tie rod. It can be reamed out to accept others. I am using on Lynchburg Lemonade with a 2.5" lift
 
Great calculator. Saving that for sure.
 
Have any calculations laying around to determine how much angle is “too much” on a birfield while you’re at it?

with 33" tires and open diff you don't have anything to worry about in this department
 
stock, 2.5", 4" can all work. depends on how your box is mounted. ZJ grand cherokee arm is beefier than the rest and takes the same "jeep" tie rod. It can be reamed out to accept others. I am using on Lynchburg Lemonade with a 2.5" lift

I thought Lynchburg Lemonade was taller! My current arm has a 1.5" drop and it's almost perfect. I don't think I'd want more than about 2" of drop or the drag link will sit lower than the tie rod. Not necessarily a problem except it will get further and further exposed to rocks the lower it gets. If the jeep tie rod is threaded 11/16-18 so I don't have to change out the drag link too that would be awesome - but I doubt I'd get that lucky! Not sure what reaming out a tie rod taper requires but I probably don't have that either.

A 1.5 - 2" drop and a 7" pitman arm would be perfect.
 

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