G56 polyurethane transmission mount - Dodge Cummins Diesel Forum
07.5 - 09 3rd Gen 6.7L Performance Parts Discussion Discussion of Performance Parts For the 6.7L Trucks...NO ADVERTISING

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post #1 of 1 (permalink) Old 03-12-2019, 03:54 AM Thread Starter
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Just finished my first test drive with my new SB SDD3250G (Incredible, by the way). When I began disassembly to swap out my smoked up Valair, I discovered one of the trans mount bolts was broken off in the transmission. Previously, when I installed my Valair, I noticed the areas around the two bolt holes on the mount plate for the bushing, were cracked or partially broken. At the time, I threw larger washers in, necause I didn't have the time. This time, I finally came up with a design that costs maybe 50 bucks, depending on what tools you have. I am not posting a writeup, as I caused a little carnage while rushing to get it done, but the design works very well, and the truck hooks up immediately. I can spin tires just by getting into it while taking off normally. Engine braking effect is far more solid, and the transmission doesn't buck or bounce on concrete highways, or backing up. In addition, I won't have to worry about broken bolts anymore. There is a noticeable increase in vibration at idle, but at no other time, under any other conditions. I assume it happened while backing a very heavy trailer. I honestly cannot believe they use such small bolts to the trans. I've done nearly a dozen clutches, and every othr vehicle had far stronger hardware.

I used 1 1/2" x 1/8" thick square tube steel, a set of off the shelf poly sway bar end link bushings from Autozone, (2) grade 10 7 1/6x3 and (2) 3/8x3 grade 10 bolts and split washers. The 7/16 bolts bolt the steel to the transmission... if you drill out the mounting bosses clear through, you will have just enough room to fit the nut on the end of the bolt on each side. I would recommend 3 1/2" bolts, mine just filled the threads in the nuts, when I cranked on it hard enough to slightly dimple the steel (no one was open at this time). The others bolt the steel to the trans crossmember. I would highly recommend the use of a drill press, which I did not have. I used a 3/4 (i think) drill bit for the bushing seat holes to account for the lip on one side. I used three poly bushings on each of the two 3/8" bolts, one above the steel, one between steel and crossmember, and one under crossmember, to completely isolate the hardware. It took a little finesse to assemble it in place, but if your dexterity is decent, it's not bad. Unfortunately, I cannot resize my photos at this time but will provide a facebook picture link soon.

07 6.7 G56 4x4 Crew. Our rodeo rig "Trevor" H&S MiniMaxx, DPF EGR delete
95 F250 351w ZF5 2wd, 300,000 and still going strong "Bessie"
2 palominos, 1 Bay, 1 sorrel.
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