Idler Arm issue and Thump Sound...???

[blackknight]

This have not been able to have a answer to this prob, so I was wondering if anyone had some input.

I have a 78 firebird. Car never been in a accident ever. I replaced all bushings and steering components about 2-3 years ago With a kit from PST. Polygraphite everything and new steering components. Everything was perfect and went together smoothly except the idler arm. I left the original idler arm in and have been driving fine ever since (20,000miles later).

I spoke with PST and they had no answer for me. I couldn't use there replacement idler arm, because the main body where the grease fitting goes into actually hits the frame and sway bar bushing(standard 1"). The body is substantially bigger then the factory one I have in the car, which is a close fit but doesn't interfere. And i have looked into replacements from like napa and they all look identical to the one PST supplied me with. The one I have works and seems fine but why would the replacement be so different looking and not fit at all!! Is there anyway that i could have a different idler arm then a standard 78? The replacement one lines up perfectly with the holes but cannot go on because it hits the frame and bushing.

Side question*******
I have rebuild just about the whole car minus the body work and a new engine. New body mounts, bushings, steering, brakes, spindles, subframes, gbraces, tranny ...etc

When I go in reverse and apply the brakes...there is a loud thunk noise that seems to come from the front passenger side. Sounds like a large shift in metal almost like you forgot to tighten arm bushings or something. Only happens once, every time i back up. There is no vibration when this happens. Just a loud noise, thump! I have checked everything for proper tightness or play. It made this noise when the car was in factory condition and the sound has remained unchanged as I have done all my projects. I have put like 55,000 miles on since i bought it. Is it the idler arm...haha????

I have beat the **** out of the car and everything has always worked great. Just these two things i have always wondered about...any input would be great, thanks.

[David Pozzi]

Some idler arms are fatter in the pivot area. I've seen the same thing. Usually you have some slop in the bolt holes that allow it to clear the sway bar. The center link should be level, if not, loosen the idler arm at the frame and raise it up till the center link is level then re tighten. Re check toe if you move the idler arm.
Check the subframe to unibody bolts, also the trans mount to cross member. We have had troubles in those areas with bolts coming loose.
David

[BonzoHansen]

I spoke with PST and they had no answer for me. I couldn't use there replacement idler arm, because the main body where the grease fitting goes into actually hits the frame and sway bar bushing(standard 1"). The body is substantially bigger then the factory one I have in the car, which is a close fit but doesn't interfere. And i have looked into replacements from like napa and they all look identical to the one PST supplied me with. The one I have works and seems fine but why would the replacement be so different looking and not fit at all!! Is there anyway that i could have a different idler arm then a standard 78? The replacement one lines up perfectly with the holes but cannot go on because it hits the frame and bushing.
This is my 77 Z28.
https://static1.pt-content.com/images/pt/2011/01/IMG_1665Small-1.jpg

I don't remember seeing an idler arm with grease fittings as you described, if I'm reading it right. Always down like this.

Moog replacement arm, hotchkiss sway bar. Dave is right, some (most) replacement arms are larger at that pivot point. Mine hit the big Hotchkis sway bar. Hotchkis told me to try another brand. Delco and the Spicer brands may have a smaller body, maybe try those. I ended up loosly installing the idler & sway, prying them apart and tightening them down. The bar just touches the grease boot.

[blackknight]

Dave,

idler arm. There is not enough adjustment for the proper fit. It just clearly did not fit. I will see if the recommendations from scott work.
I will check the tightness on those bolts in the early spring when it is not 7 degrees out like today here in NY. Thank you for your recommendations.

Scott,
The Replacement I received looked just like the one you have pictured. Does not fit, not even close. I will look into the other brands with possible smaller Pivot area. Thanks. Maybe one of them will fit, spicer or delco. I also have a front frame brace under the sway bar bushings, so hopefully something clears. If the factory one does, something should.

[SLO_Z28]

For the life of me I cant find it but Hotchkis has a TSB about this. I think the one that classic industries sells has the smaller body. One of the major manufacturers out there sells a idler with the smaller diameter body. Be sure to measure when replacing this, as its placement is very important to steering geometry. It needs to be parallel.