Monday, June 12, 2017

Let's get ready to RUMBLE!!!!

Like so many blogs, I haven't posted anything new in quite sometime.
I thought instead of rehashing a rebuild I'd blog about some troubleshooting.
The very first time I drove the car down the main straight at Texas World Speedway, a distinct "rumbling" sound presented itself at around 4500 rpm or so in fourth gear.

I remembering thinking to myself, " Oh Sh!t, what is that? I need to pull into the pits". Then I thought to myself "and do what?". I just kept my foot into it and was kinda curious as to what was to next.
Other issues at the opposite end of the car got my attention and took me out of the race. I'm referring to earlier blog posts about oil leaks and such. So I really didn't spend my energy and thought on the rumble.

In the course of my engine rebuild, I swapped gearboxes and diffs as well as had the driveshaft balanced and new u-joints installed on both ends. I need to write a posting about the headaches I encountered with these seemly benign tasks. So back to the rumble, it is still there.

One thing I hoped would have made it go away was one of my "competition" axels had a loose bolt that holds the yoke on. The axel is designed in such a way that the bolt cannot back completely out as it is under the yoke. The bolt in question holds a flange to the end of the axel and the yoke is then bolted onto this flange which in turn covers up the bolt. Still, loose is NOT a good thing but as I was to find out on my first outing, it was also NOT the source of the vibration.

I'm thinking perhaps and out of round tire or wheel that is not true but I think when I had the car on the dyno, the dyno operator would have said something and in my videos from the back of the car, I see no vibration. So I really don't think it a wheel or tire issue. I was planning on simply rotating the tires to check but haven't as of yet.

My next thought goes to the differential mounts. They are almost rock solid mounts and perhaps I'm just not used to this. Or do I have it too stiff a mount? I know on the factory rubber mounts, the nut bottoms out before crushing the rubber. Maybe I need this gap?

Another area I what to look into is on the rear radius arms. Both arms are custom rods with heim joints. The passenger side I can twist by hand but not the driver's side. So maybe I have an alignment issue or a worn heim joint.

I'll get back with what I find out.

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