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Shifter mount saga: Part 1 (because of the picture number limits per post, I will break this picture intensive build project into a couple parts/posts.)
Picture 1: finished mount from above.
As many here already know I am helping Gary P. with his F1 restomod build. Gary chose an engine and transmission from a 2007 Mustang GT donor: a 4.6 3V Mod motor and it's companion 3650 5 speed stick. This all aluminum engine and tranny are light weight and powerful, but present some challenges that have yet to be addressed by the aftermarket, i.e. engine mounts, headers, tranny crossmember. Those solutions have been discussed previously. Now another major hurdle to be conquered is the shifter location. Ford's variant on the T-5, the 3650 has a rather unique shifter location/ mounting arrangement to conform to the Mustang's long nose/rearward driver seating location and Ford's desire to reduce NAV (Noise And Vibration) inside the vehicle to as low as possible. Instead of the shifter pivot mount being part of the transmission case and moving the gears using internal shifter rails, like most T5s, they used a separate external shifter mechanism that is attached to the transmission tailshaft housing at the front by a soft urethane bushing at the end of long of arm and at the rear it is bolted to the car's floorpan behind the transmission by a saddle around another large soft bushing. The shifter pivot is suspended between these 2 mounting points and a heavy bar connects the bottom of the shifter to a socket wrench style U joint trunion at the end of a rod protruding from the rear of the tailshaft case. The shifter turns this rod and slides it in and out. This arrangement places the shifter pivot about 6” behind the front driveshaft U-joint, which would place it behind the front of the seat(s) in the F1. It also makes the shifter position and operation rather “vague” due to the soft mounting and one end of the mount moving with the engine/trans and the other end with the body. Not exactly desirable in a hot rod.
Picture 2: Hurst short throw shifter for OEM application showing Mustang mounting arrangement and as modified for our use.
I did a lot of internet searches and found a picture of how someone had flipped the shifter around to mount this same engine and tranny in a F5 Cobra Kit car. Their installation attached the flipped shifter to a large plate and framework straddling the transmission and bolted to the Cobra frame, using the OEM mount points and bushings to mount the shifter assembly to the plate. IMHO a rather large and cumbersome mount that still was detached from the separately moving engine/tranny assembly, but did provide an inspiration for a solution to our dilemma. What if a compact mount for the flipped shifter pivot could be fashioned that mounted directly to the transmission? It would place the shifter pivot about 12” ahead of the Mustang location, nearly in the same location as an original F1 floor shift!
We needed a way to mount it to the tranny, the first and major one of our goals. Examining the transmission carefully it was obvious that there were no case bolts that could be pressed into double duty. Strike 1. A structure that could clamp around the tranny was considered, but rejected as too complex. Strike 2. Then we noticed that there were two cast in horizontal tabs with holes in them sticking out on each side of the transmission, The front two had wiring harness clips snapped into them, the rear ones were bare. These were substantial in design, much more robust that needed to attach wires to and machined flat on the bottom. Checking carefully after removing the wiring clips it was happily determined that the bottom of these 4 tabs were all parallel and at the same height on each side. I don't know their true function, but I'd guess they may have been used to temporarily attach some sort of assembly line fixture to the transmission. They were a bit forwards of an ideal location for our shifter, so we then went looking for a possible 3rd mounting point further aft. There were 2 horizontal stiffening “fins” at the tail end that were almost exactly 1/4” lower than the side tabs that could be drilled and pressed into service with 1/4” spacers. We had found our mounting points! Home run!
Now we needed to fab a mount structure to prove the concept and locate the best mounting point in 3-D space for the shifter to function correctly. I made an oversized plywood dummy mounting plate, and after blocking it in position we fabbed a mounting structure we'll call the beta version, from 1/8” plate and 1/2” x 1/2” square tubing.
Picture 3: beta version mount
This beta mount with the wood plate reproduced in aluminum would have worked but the size and shape disturbed my design sensibility. I could do better.
Picture 4: studying the beta mount for redesigning
Part 2: the redesign
I spent much time the next week redesigning the plate dimension to the minimum necessary. I reduced it down to 6”x 6” from the initial 5.5 x 10.5” of the first dummy plate (after trimming) and increased the thickness to 3/4”. A full size cad drawing was made and I fabbed a new dummy plate from 3/4” MDF with temporary biscuit joint extensions so it could be clamped to the beta structure. Tony B. stopped by Gary's to see what we were up to and to pick up the cad drawing. Tony (tonyb55 on FTE) has his own F1. He is an excellent machinist and volunteered to machine the needed aluminum plate for Gary.
Picture 5: The cad drawing for the plate.
Picture 6: The two piece plate Tony machined with aligning dowels.
Picture 7: The plate joined together. Tony counterbored the bolt holes so allen head cap screws would be flush with the top surface and chamfered the edges for a finished appearance. Beautiful work!
Mount V. 2.0
While waiting on the aluminum plate machine work we used the MDF dummy plate to do the redesign of the beta mount to V. 2.0. Two support angles were cut from split 1”x2” rectangular tubing, drilled and bolted to the dummy plate and the temporary MDF extension was used to clamp it to one side of the beta mount, the other side of the beta mount was partially cut away for working room, and a length of 1” x 1/8” bar stock was tack welded to the remaining upright stubs to support the new upper structure. A pattern was made and a trapezoidal shaped plate cut and tack welded between that bar and the plate support angle. Then the MDF plate extension piece was unclamped and removed, the other side of the lower structure cut down and the new support structure built similar to the first side. Note that the shifter pivot is required to be located offset to the passenger side to operate properly, and the tranny case is nor symmetrical so the two sides of the mount are not mirror images of each other.
Picture 8: The tacked together V 2.0 with the newly machined aluminum plate replacing the MDF dummy. Compare to picture 3.
To complete the mount redesign, the removed upper horizontal and front diagonal tubes of V. 2.0 were replaced and the cut uprights trimmed in the lower structure, new sheet gusseting added to the back end to strengthen and stabilize everything for the “occasional” power shifts Gary “might” throw. The mount was disassembled and removed to the bench where all tacks were fully welded, the welds ground clean and the parts painted before being reassembled for the final time (for now at least) on the transmission.
Picture 9: Driver side view of completed mount V. 3.0
Picture 10: Rear view of mount V. 3.0
Picture 11: Passenger side view of V. 3.0
We are both very pleased with the finished product, it met all our design goals including size, function and appearance. A big thank you to Tony B. for his contribution.
Nice and clever solution to the problem Ax!! Always nice when you have the ability or a friends ability to make parts to overcome the inevitable challenges.
Yes, it's good to have friends, especially when breaking new ground! When I do a write up like this I try to cover the thought process and work that went into it to hopefully inspire others, rather than just post a "Hey look what I can do..." picture.
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