3-Link Rod Ends and Should I be Looking at a 4-Link Instead

[boostin1989]

I'm in the middle of designing a 3-link for my car. For the rod ends I went with Johnny Joints because the car is for the street and I wanted to avoid the harshness of conventional rod ends. It'll have a twin turbo LS (800-900hp), manual trans and a 9" axle. I have two questions:

1. The Johnny Joint through bolts seem really small. The 3/4" shank models I purchased for the lower control arms will only accept a 7/16 through bolt. I've done the calculations and it should be fine but I would like some input on this, they just look small. The single upper link would be the 1" shank model which has a 9/16 through bolt.

2. At this power level should I be looking at going with a 4-link instead? I've been contemplating the torque load path through the axle housing and am wondering if the 4-link would be a better choice.

[Ron Sutton]

Will you be drag racing the car with slicks?

[boostin1989]

Currently I don't plan to but I wouldn't rule it out. If I do then I assume the 4-link is the way to go.

For now let's assume it'll never see slicks (but maybe a 295 drag radial).

[Ron Sutton]

Currently I don't plan to but I wouldn't rule it out. If I do then I assume the 4-link is the way to go.

For now let's assume it'll never see slicks (but maybe a 295 drag radial).


Hmmm. Twin turbo LS (800-900hp), manual trans, clutch drops on 295 drag radials ... and guessing at 3000# plus. IMHO the top link in the 3-link will be marginal. FYI: The top link or links see serious pulling & lifting load. You'd be putting a lot of force on the threads of 1 link & 2 rod ends. A 4-link spreads the load over 2 links & 4 rod ends, so they see half the force each.

I'd offer up the suggestion to consider building upper mounts on the housing & frame for 3-link & 4-link (lower links are the same) ... like I do in my Street Warrior cars. Then you can run the 3-link for street, track days, autocross, etc ... and swap on the 4-link uppers for drag strip excursions.

Just an idea. Best wishes.

[wendell]

Given that I've never heard of a failure in TA running jumbos, I wouldnt sweat it.

[Mateospeed]

As usual, I'm win Ron. If you really care, do both.

I'll also add another point, though - if you're serious about the handling of the car, you won't be dragging it. If you're serious about dragging it, you won't be turning much. The 2 setups are just too different - switching from one type of event to another is just too much of a hassle!

So, take a good look at your wants and desires, and build a 3-link if you're going to ask it to turn, and a 4-link if you're not that concerned about it.

-Matt