Friday, December 2, 2016

Triumph Spitfire Chassis Restoration #14

I have finally defeated my mortal enemy. There are too many posts that covered my differential restoration but they all essentially boiled down to the same problem - the rear bushings. In short, these things go in very tight and are a real bear to get in there. Once again my favorite forum came to my rescue and provided me the correct formula to get the bushings in. Unfortunately, I pressed one through too far, preventing the differential from fitting into its place in the frame. I could not get the bushing pushed back out and I started to tear the whole thing apart in preparation for burning the bushings out and starting all over again.

But, as the saying goes, "the right tool for the right job" saved the day. And, of course, the fact that my garage mate had the 20-ton press that I needed helped! With his help, we were able to position the differential just right and pushed the bearing back the other way just a bit.

A beast of a press. Rated for 30 tons, but it has a 20 ton bottle jack on it.

Another problem that I had was that the mounting bolt would not fit through the bushing sleeves. My guess is that I had mushroomed the ends a bit from all of the banging and pressing and all of the other torture that I put those things through. But, a few quick swipes with a rat-tail file and it was fine.


The rat-tail file I used.

And the bolt goes in.

And, finally, the inner sleeves were just a bit too wide to fit into the frame with doing some serious banging. I assumed this was supposed to be a rather tight fit to prevent the differential from moving around too much back there, but I wanted the bolt to be able to compress the frame a bit to capture the differential instead of it being banged into the frame.

I did some quick measurements of the mounting points in the frame using the "inner" side of my 6 in. Digital Caliper. I then measured the bushing sleeves using the "outer" side of the caliper. I carefully used a flap disk to make the two nearly match.

You can just see the light grinding done to the inner sleeve (and some of the rubber..whoops!).

Quite some time ago I had purchased the polyurethane differential mounting kit (P/N DMK9/U) from The Roadster Factory and I was finally getting to use it. To help me with the weight, I flipped the frame upside down to allow the differential to rest in its mounting points. I placed the upper mounting bushings for the front mounts down and put the differential in place.

The upper (frame flipped here) mount goes on first.

The differential front mounts are like a sandwich of bushings - the lower mount, then the differential mounting plate, then a polyurethane washer, then a metal washer, then the nut. The original metal washers were in good shape and quite a bit beefier than the ones that came with the mounting kit. Given my desire for using original parts as much as practical, I went with them. I didn't believe that the thickness would impact the stack up or thread engagement for the nyloc nut.

Thickness comparison. A bit easier to see the difference in person.

Once I had the differential front mount all sandwiched up, it was time to get the rear bolt in. I used a generous amount of Permatex Anti-Seize and coaxed the bolt through all of the holes using a dead-blow hammer.

Rear bolt in and tight.

Then is was back to the front mounts to get them bolted in.

The passenger's front mount all done up.

After that, I flipped the now much heavier frame over. I touched up the paint on the differential as best as I could since I had nicked it and banged it around so much trying to get the bushings taken care of. After that, I moved on to the front half.

A milestone! The first real part re-installed.

First order of business up front was to get the front suspension turrets back on. I had saved all of the old shims, but bought new bolts given the problems that I had found with the old ones. I purchased Grade 8 hardware (bolts, flat washers and lock washers) because I figured this was high stress stuff and would benefit from the better quality hardware. What I didn't consider, however, was that the bolts were now harder than the threaded holes I was putting them into and, therefore, would more easily strip the threads of those holes.

This is the kind of job where you have to start each bolt, but not tighten any of them until they get set. Then, slowly tighten them all in an alternating pattern. Maybe this is why they were stripped...in the factory by guys trying to get the job done? Anyway, while doing this I thought I had stripped out the driver's side upper mounting hole threads with the harder bolts. While I did do some damage, it was only the first few threads and there was a lot of good thread left.

Upper mounting bolt, with the original shim installed.

Passenger's side mounting bolts.

Finally, I attempted to install the lower wishbone and suspension sub-assembly. Unfortunately, this didn't work out for me. For some reason, even though the hardware that's going back on is the same stuff that I pulled off, it wouldn't fit.

The front (right) stud is in its place. The rear is not...by quite a lot!

Close-up of how far the stud is off. And, yes, I scratched my paint. Not happy.

In discussion with my favorite forum, we are under the impression that the bushings that mount the lower wishbone to the bracket with the stud are not centered about the wishbone. Since I have polyurethane bushings in this application as well, and they are two pieces, I'm not sure that I agree. But, I couldn't see the problem the other night and, not wanting to make a bad decision trying to fix it, I stopped work for the evening.

Both boys are playing basketball again this year and the games are set up such that there is one on Saturday and one on Sunday. I am also helping coach my youngest's team. Given all of that, weekend garage time will be curtailed, but I still intend to go at least most of one of the days. We'll see how it works out.

As I left it. Well, I did put the wrenches away!

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