Project Update for March 18, 2013: I started writing this post two weeks ago but we have been so busy at Vorshlag it took several attempts to finish it (finally posted on April 2nd!). In the end it got pretty big and turned into a four part post. This is because we've done several repairs, updates and testing of new parts and tires on the 2011 Mustang GT since the last thread update. We also ran the red Mustang at another NASA Texas weekend March 16-17th, with another win and a new track record in TT3. As always, any picture in this thread post can be clicked for an "Extra large" high resolution version, so if you see something you like, click it. Let's start with some new Whiteline parts to test.
Whiteline Updates + New Trans Bushing Insert
We finally had time to add the Whiteline transmission bushing insert to the stock Mustang trans mount. The factory rubber trans mount bushing has massive voids that don't help the stiffness of this bushing one bit (see the picture, below left). Air is a terrible bushing material.
Why does this matter? Well the Getrag MT-82 has a remote body mounted shifter, and the drivetrain is mounted on its own bushings. So when the transmission is loaded up (either with lateral g forces or under torque load) it moves relative to the body, and the shifter doesn't always then line up properly when you are trying to shift loaded up. This has been plaguing us for a while, and the "just add an aftermarket shifter" option doesn't fix the fact that the transmission is moving relative to the remote mounted shifter. At the NASA @ MSR-Houston event in January both Amy and I figured out quickly that we needed to shift earlier or later than we wanted to avoid shifting while in a high speed corner - because we would miss the shift every time.
BONK! Frustrating.
Whiteline sent us the first prototype for this brand new KDT928 part, which is similar to other bushing "void inserts" they make for other cars. They were waiting for our feedback before they went to production - we gave them a big "yes, please!". This is an elastomer bushing insert that just pops into place and fills the air gap in the factory rubber bushing. We don't have official pricing yet but I was told the price "should be about the same as similar inserts we make", (so about $35). I have an open order for more, because this thing just flat-out works. Super easy to install (no tools, no effort!) and it firms up the transmission mounting nicely. Now installing this will add a
little extra NVH (noise-vibration-harshness), just in case you are wondering.
Amy picked up the Mustang after we installed the insert and immediately came back after leaving the parking lot and said "Hey, something is different here...?" It isn't bad at all, just a little more NVH, and nothing like going to a full poly trans mount bushing would be. It just removes some of the air gap and firms the mount up a good bit. We should have these in stock before too long and I will post up in this thread when they are ready.
And while I teased the multiple shifter bushings/housings that we acquired and durometer tested last time, we didn't get time to install these before this NASA event. We will have it in this before this coming weekend's Five Star Ford / ECR track event (April 6th). The Whiteline transmission bushing insert alone already made big improvements by itself, but when you squeeze the factory mush bushing in this shifter mount location it just begs for an upgrade.
The other new Whiteline part we tested was a revised set of mounting brackets for their rear swaybars. We had one of the earliest production Whiteline rear swaybars, and as you know if you have been following our build for this S197 Mustang, it mounts very differently than the OEM rear swaybar. Instead of mounting the bar to the body and the endlinks to the axle they swapped it around - the bar mounts to the axle and the endlinks mount to the chassis. Some folks poo-poo this mounting method on the WL bar, but it is in fact a
very common method for mounting of factory rear swaybars on solid axle RWD cars. The side benefit on the S197 is that it opens up a lot of inboard wheel room for wider rear wheels... this is part of how we are able to fit 12" wide wheels under the rear fenders (for a race set-up only - this is
not a streetable size, due to some clearance issues in extreme droop situations with a wheel this far inboard).
Anyway they have now revised the height of the mounting brackets to space it away from the axle slightly, to free up room elsewhere. We installed these new parts and it works great.
Last but not least we inspected the elastomer bushings in the Whiteline Watts Link propeller, which looks flawless after 8 months of hard use. Some new grease and back in it goes. Why did we have the Watts Link off? Read below to see...
Axle Housing Reinforcement + LCA Bracket Welding
So the 8.8" Ford rear axle housing came from the factory in bare steel, and that quickly rusts - even here in Texas. This always bugged me and I wanted to paint the bare metal earlier, but we never had time to yank the whole rearend and do it right. Now, though, we had an excuse... we were doing a differential change (Torsen T-2R), welding the axle tubes and welding the LCA relocation brackets. This made it the perfect time to yank the entire rearend housing, pull out all of the guts, and clean up the surface rust before the welding started.
Left: This picture shows the rusty axle in the first week of ownership, less than 50 miles on the car! Right: Visibly worse last week
The proposed welding of the axle tubes caused a bit of controversy when I "teased" these pictures early on Corner-Carvers. Do the axle tubes even
need to be welded to the center section?, some asked. And if so, what procedure do we use to weld them without causing any added stress? Should there be fixtures, could we "warp" the housing welding these ends? There were force diagrams and equations bantered about... but I just don't think it is all that complicated. It did not warp and we have raced the car since and nothing exploded from added stresses. This welding procedure is common prep on thousands of drag race cars, autocross cars, and even road race/track cars, and I think it is just a small bit of insurance against axle tube movement.
We've been paint-marking the tubes for a while, as they are only held in by a press fit + two small rosette welds on each tube. You look at almost any race-prepped or fabricated housing and the tubes are always welded in place. I'm fairly confident we haven't added some uber-stress riser that will likely crack and make the axle fall apart. It made it through a NASA race weekend, another ECR track day (March 23), and weeks of street driving already without any cracks or issues, but we will keep an eye on the weld, just in case. If the axle somehow explodes from the stresses added by this weld I guess I will have to eat crow. Do all of you need to do this to your S197? Of course not. But with the added lateral loads from 315 mm A6 Hoosiers, the ballasted up 3800+ pounds we race with in TT3, and the lap times we are running now, we felt it was worth the effort.
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