drag link geometry and Questions

[Blue68]

Guys,
Some time ago, I replaced the front crossmember on my '68 C10 with one from a '75, including the drag link and tie rods. I'm not real sure, but there are a couple of quirky things about the steering that I've been noticing the last two months (finally driving it more). One, when I turn full left/right one of the tires scrubs so hard (like it's gone too far for the radius) it actually slows the truck down. Like when backing out of the drive way, most cars roll, I have to gas my truck. Again, it's only at near full and full lock. Same deal going forward. It also seems to have some slight bump steer. And the drag link/center link actually rubs against the crossmember. The link is level, so I think my pitman arm and idler/follower arm are fine (used to be a manual steer truck, now has power and is lowered as well).

Could someone measure a stock '68 Chevy center link for me?

I'm pretty sure the drag link is off the '75 since the inner tie rods are stock '75 pieces (no adapter sleeves). But I'm thinking the pitman arm and idler arm are '68 pieces. Maybe that's why there's scrubbing?

Any front end geometry wizards out there that could provide guidance?

[68w/sbc406]

i am going to keep my eye on this one, i am doing 81 parts on my 68 and dont want any problems

[Blue68]

Thing about it is I'm not sure why there would be a problem. The idler arm part numbers seem to be the same from '67 - '82, so that shouldn't be a problem. The center link is from the same truck as the crossmember, so the geometry for it should be the same in relation to the control arm lengths and tie rod positions. I'm getting down to the pitman arm being a potential culprit since it seems to be a different part between the the '68 and '75 models. But I don't know what's different about them.

[FirstGen]

hard to say what the problem could be... I just did a 6 lug disc conversion using componets from a 1990 suspension. I used the stock 68 drag link and then used 1990 tie rods (I actually shortened them to give me the proper alignment since it lowered). Have you taken the truck to be aligned yet? If you tell NTB that you work at a dealership they will do a one time alignment for 39 bucks. They will be able to tell you more than likely what if anything is causing problems.

I would say that it is not really un-usual for a truck to need some throttle to move under full turning...

[kwmech]

Are you using the 68 centerlink or the 75? The tie rod ends changed in 71 when they went to disc brake. When I did the disc swap on my 69 1 ton to 78 stuff, I had to change the center link, pitman and the idler.

[Blue68]

I don't think I swapped the idler, looks like it's the same part through '82. Center link has to be different or the inner tie rods wouldn't fit. The pitman is a part I really can't remember what I did about.

I did do some measuring, and measuring from the frame, the driver side of the center link at the inner tie rod seems to be about 1/8 inch lower than on the idler side. Maybe this is why it's rubbing on the crossmember.

So, what/why are the differences between the 68-72 and 73-87 pitman arms when the idler arm part number spans 67-82?

[68w/sbc406]

i got my power steering set up off of an 86 and put it on my 68, havent had any rubbing problems. i cant see how the pitman arm would be messing you up.

[Blue68]

If the pitman arm is lower, it would put the radius arc off relative to the control arms causing bump steer. Also, if it is lower or longer, it could be causing my rubbing against the crossmember. It takes a sizeable bump to get anything that is unsettling so it's not like it's a huge amount.

As for the tire scrubbing at full turn, maybe it's normal. I've driven the truck more in the last two months than the previous 3 years combined. So I may have just missed something there.

[kwmech]

According to the LMC catalog [I do not have my real books at home] the 67-72 pitman is the same which would mean even through disc brake. From 1973 to 87 is a different number. 1/8 of an inch would not make that much of a difference in the geometry in these trucks, the frame could be off more than that just because of its age and mileage.