MAV
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Today, I finally finished a project that has been nearly seven years in the making. I ordered my GT350 in September 2015, and before I even drove the car, one of the first mods I considered was to match the 8250 redline with a 4.56 gear. Since no one made any aftermarket gears for the Super 8.8 for a couple of years after the S550 was introduced, and the car was under warranty until last year, this project hasn't been on the front burner until recently.
I recently came across an iron case 3.31 trac-loc on the cheap, so I bought it and also bought a set of Richmond 4.56 gears (part number 49-0214-1), a Ford Performance Torsen T2R differential (part number M-4204-MT), a Ford Performance Super 8.8 bearing and shim install kit (M-4210-B3), and an axle bearing and seal kit (M-4413-B). I also picked up a new 2018+ pinion flange (HR3Z-4851-B) and a rear cover with the cooler fittings to go with my Track Pack 2016 GT350 (FR3Z-4033-B).
Much credit to forum member @JohnVallo for his excellent detailed posts on building and experimenting with several aftermarket ratios for his GT350. Since he goes into great detail about the pros/cons and building of the Super 8.8, I won't repeat that information here with the exception of a couple of pics of the housing and gears along with the final pattern that I settled on.
Those were the initial test patterns, and I added another shim for a total of .037 before the final pattern (sorry, didn't get the coast side - you can see it in the "ghosted" imprints of the compound):
I have only been to the drag strip once making two passes on the stock tires, but the car wheel hopped so bad that I decided not to run it any more for fear of breaking something. The only mods on the rear suspension are a BMR CB005 lockout kit which helped with wheel hop on the street, but not on the track with all the sticky traction compound. I suspect that's when my differential mounting ears shifted as on most cars with the stock hardware and bushings.
Following this thread, I decided to drill out the front bushings to allow for a 9/16 bolt-through. I wanted to keep the stock bushings for NVH reasons (and I don't track the car), but I also wanted to upgrade all four differential mounting bolts. I have seen the spacers that are available for the rear bolts, but since the bushing bolt hole is 17.3 mm, I thought why not just go with a 16mm bolt that is much larger and takes up most of that space?
Some have drilled the ears of the differential cover for a bolt-through design, but that also requires some work on the front of the ears to make a flat surface for then nut to seat. I thought it would be easier to simply drill and tap the ears for a M16-2.0 bolt. So that's what I did. For the stock bushings, a 12.9 M16-2.0 x 100mm bolt fits perfectly to the holes in the bushings and the ears drilled to 14mm and tapped to size.
You can see in the second picture above that the gap is minimal on a 16mm bolt.
For the front, I drilled out the threaded factory bushings to 9/16 and used a 9/16-18 x 4" bolt with a nylock nut for a true bolt-through design as Kelly describes in the above thread. I torqued both fasteners to 150 ft/lbs, and although the M16 bolts could have surely taken a little more, I didn't want to risk damaging the threads in the aluminum differential cover.
In order to accomplish all this, I figured it would be easier to simply drop the entire subframe out of the car. Having a lift meant that it was easier to get under the car to do a lot of work, but not having a multi-extendable transmission jack also meant I had no way of easily lowering the old differential out of the car and raising the new one in. With the cradle on the floor, I could simply use my floor jack to lower and raise the diff into position and also not have to worry about lowering the front of the cradle enough to drill the bushings.
Taking your time to lower the subframe is of utmost importance. I was a bit disheartened at the difficulty not mentioned in any of the "how to" videos online or even some of the write-ups I've seen. The most difficult parts of the project for me were dealing with the parking brake hardware and breaking the axles loose from the hubs. I literally spent half of the three days of this project trying to get the driver's side axle out of the hub, which I never actually did. The passenger's side came out with some PB Blaster and a couple of whacks with the hammer. I ended up taking the driver's side axle, hub, and knuckle out as a single unit.
Ford engineers should be taken out back and beaten with a rubber hose to have designed a splined mating system that is not sealed from the elements. My car has been driven in the rain twice in six years, yet the left side axle is permanently rust-welded to the hub. I use the word "permanently" because I beat on it in the car (with the old nut on it to protect the threads), tried a puller, soaked it with penetrating oil overnight, beat on it some more the next day, pulled it out of the car as a unit as mentioned above, soaked it with more PB Blaster, and eventually hit it enough that it boogered up the threads anyway. Once they were screwed, I *really* starting railing on it with the hammer to no avail. All I accomplished was to make the threads irreversibly damaged.
At that point, I could either try grinding away the old threads or destroy the hub and axle by heating them to the point of damaging the bearing and its seals to break them free. This is what I'll eventually have to do when one or the other goes bad. So, I spent most of the day yesterday grinding bad threads and trying to get the nut to thread on to good threads without cross-threading. It was a mess. It of course cross threaded anyway when I tried to put the nut on today, so I took a 1" impact wrench and stripped it completely pulling the nut back off. Ground down the threads again, and when I put on a new nut this time, it went on with little fuss. Who knows?
The other nuisance is the parking brake clip holding the cable into the bracket. The spring will compress just enough to make you think it's clear, but it's not. Then, there are three "fingers" holding the cable to the bracket. Good luck in compressing all of them to get the cable clear of the bracket. Maybe Ford sells a tool that makes that whole ordeal a lot easier, but I don't have it, and I would have paid dearly to get one.
I guess I should mention the QA1 CF shaft. It was mildly difficult to get tools into the socket screws to get proper torque on them, but not impossible. The biggest pain installing a new driveshaft is the back and forth to set the parking brake to torque the bolts you can get to, and then releasing it to turn the shaft to get to the others, then setting it again, etc. Just a lot of back and forth and time consuming but not all that big of a deal. The QA1 driveshaft is nothing short of a work of art. It's beautiful. So beautiful in fact that I forgot to take any pictures.
I am mildly concerned with my Kooks headers and cat back exhaust not having a heat shield to protect the shaft from baking, mainly at the X-pipe. If anyone has any input on that subject, please let me know.
Impressions:
Phenomenal! The car literally feels 1000 lbs lighter with the 4.56 gears. I've only driven it around town to break in the gears and bed in the new Power Stop Z26 brake pads (SO FREAKING TIRED OF BRAKE DUST!!!), but difference in the in-town driving is amazing. The gears do have some whine, but it's not unbearable. The 3.73s were somewhat noisy with the CB005 kit, but so far the 4.56s are noisier. I read that the stronger bolts could add some NVH, but I don't know how that would be the case. Maybe the CF driveshaft adds some noise. The gear pattern is good, and I'm going to wait to judge it until the break-in period is over and I've changed the oil. It could be that gears that low are just inherently noisier than higher ratios. We'll see. I don't care. Sounds more like a race car.
As John said in his 4.56 install writeup, it is difficult to time the gear changes and clutch releases now. I don't have the sounds that he experienced, but the car is much more sensitive to the timing of the clutch release and rolling into the throttle afterward. There is a noticeable "flare" when shifting, and it *almost* feels like it's part of the tuning of the car. John mentioned that he had previously installed the Steeda clutch spring, and I may need to do that now as well, although I had become quite accustomed to the factory clutch pedal action and had gotten the timing down for smooth shifts. I do think the two piece flywheel has something to do with it, again referencing John's experience and writeup.
Bottom line is that the car is MUCH more responsive with these gears. I'll never know what difference the new driveshaft made because I don't have the reference point of using it with the stock 3.73s, but I'm sure the two together contribute greatly to the increased response. Unless the noise gets worse, I have zero regret in this project. It will be fun the first time I hit redline once the gears are broken in.
I recently came across an iron case 3.31 trac-loc on the cheap, so I bought it and also bought a set of Richmond 4.56 gears (part number 49-0214-1), a Ford Performance Torsen T2R differential (part number M-4204-MT), a Ford Performance Super 8.8 bearing and shim install kit (M-4210-B3), and an axle bearing and seal kit (M-4413-B). I also picked up a new 2018+ pinion flange (HR3Z-4851-B) and a rear cover with the cooler fittings to go with my Track Pack 2016 GT350 (FR3Z-4033-B).
Much credit to forum member @JohnVallo for his excellent detailed posts on building and experimenting with several aftermarket ratios for his GT350. Since he goes into great detail about the pros/cons and building of the Super 8.8, I won't repeat that information here with the exception of a couple of pics of the housing and gears along with the final pattern that I settled on.
Those were the initial test patterns, and I added another shim for a total of .037 before the final pattern (sorry, didn't get the coast side - you can see it in the "ghosted" imprints of the compound):
I have only been to the drag strip once making two passes on the stock tires, but the car wheel hopped so bad that I decided not to run it any more for fear of breaking something. The only mods on the rear suspension are a BMR CB005 lockout kit which helped with wheel hop on the street, but not on the track with all the sticky traction compound. I suspect that's when my differential mounting ears shifted as on most cars with the stock hardware and bushings.
Following this thread, I decided to drill out the front bushings to allow for a 9/16 bolt-through. I wanted to keep the stock bushings for NVH reasons (and I don't track the car), but I also wanted to upgrade all four differential mounting bolts. I have seen the spacers that are available for the rear bolts, but since the bushing bolt hole is 17.3 mm, I thought why not just go with a 16mm bolt that is much larger and takes up most of that space?
Some have drilled the ears of the differential cover for a bolt-through design, but that also requires some work on the front of the ears to make a flat surface for then nut to seat. I thought it would be easier to simply drill and tap the ears for a M16-2.0 bolt. So that's what I did. For the stock bushings, a 12.9 M16-2.0 x 100mm bolt fits perfectly to the holes in the bushings and the ears drilled to 14mm and tapped to size.
You can see in the second picture above that the gap is minimal on a 16mm bolt.
For the front, I drilled out the threaded factory bushings to 9/16 and used a 9/16-18 x 4" bolt with a nylock nut for a true bolt-through design as Kelly describes in the above thread. I torqued both fasteners to 150 ft/lbs, and although the M16 bolts could have surely taken a little more, I didn't want to risk damaging the threads in the aluminum differential cover.
In order to accomplish all this, I figured it would be easier to simply drop the entire subframe out of the car. Having a lift meant that it was easier to get under the car to do a lot of work, but not having a multi-extendable transmission jack also meant I had no way of easily lowering the old differential out of the car and raising the new one in. With the cradle on the floor, I could simply use my floor jack to lower and raise the diff into position and also not have to worry about lowering the front of the cradle enough to drill the bushings.
Taking your time to lower the subframe is of utmost importance. I was a bit disheartened at the difficulty not mentioned in any of the "how to" videos online or even some of the write-ups I've seen. The most difficult parts of the project for me were dealing with the parking brake hardware and breaking the axles loose from the hubs. I literally spent half of the three days of this project trying to get the driver's side axle out of the hub, which I never actually did. The passenger's side came out with some PB Blaster and a couple of whacks with the hammer. I ended up taking the driver's side axle, hub, and knuckle out as a single unit.
Ford engineers should be taken out back and beaten with a rubber hose to have designed a splined mating system that is not sealed from the elements. My car has been driven in the rain twice in six years, yet the left side axle is permanently rust-welded to the hub. I use the word "permanently" because I beat on it in the car (with the old nut on it to protect the threads), tried a puller, soaked it with penetrating oil overnight, beat on it some more the next day, pulled it out of the car as a unit as mentioned above, soaked it with more PB Blaster, and eventually hit it enough that it boogered up the threads anyway. Once they were screwed, I *really* starting railing on it with the hammer to no avail. All I accomplished was to make the threads irreversibly damaged.
At that point, I could either try grinding away the old threads or destroy the hub and axle by heating them to the point of damaging the bearing and its seals to break them free. This is what I'll eventually have to do when one or the other goes bad. So, I spent most of the day yesterday grinding bad threads and trying to get the nut to thread on to good threads without cross-threading. It was a mess. It of course cross threaded anyway when I tried to put the nut on today, so I took a 1" impact wrench and stripped it completely pulling the nut back off. Ground down the threads again, and when I put on a new nut this time, it went on with little fuss. Who knows?
The other nuisance is the parking brake clip holding the cable into the bracket. The spring will compress just enough to make you think it's clear, but it's not. Then, there are three "fingers" holding the cable to the bracket. Good luck in compressing all of them to get the cable clear of the bracket. Maybe Ford sells a tool that makes that whole ordeal a lot easier, but I don't have it, and I would have paid dearly to get one.
I guess I should mention the QA1 CF shaft. It was mildly difficult to get tools into the socket screws to get proper torque on them, but not impossible. The biggest pain installing a new driveshaft is the back and forth to set the parking brake to torque the bolts you can get to, and then releasing it to turn the shaft to get to the others, then setting it again, etc. Just a lot of back and forth and time consuming but not all that big of a deal. The QA1 driveshaft is nothing short of a work of art. It's beautiful. So beautiful in fact that I forgot to take any pictures.
I am mildly concerned with my Kooks headers and cat back exhaust not having a heat shield to protect the shaft from baking, mainly at the X-pipe. If anyone has any input on that subject, please let me know.
Impressions:
Phenomenal! The car literally feels 1000 lbs lighter with the 4.56 gears. I've only driven it around town to break in the gears and bed in the new Power Stop Z26 brake pads (SO FREAKING TIRED OF BRAKE DUST!!!), but difference in the in-town driving is amazing. The gears do have some whine, but it's not unbearable. The 3.73s were somewhat noisy with the CB005 kit, but so far the 4.56s are noisier. I read that the stronger bolts could add some NVH, but I don't know how that would be the case. Maybe the CF driveshaft adds some noise. The gear pattern is good, and I'm going to wait to judge it until the break-in period is over and I've changed the oil. It could be that gears that low are just inherently noisier than higher ratios. We'll see. I don't care. Sounds more like a race car.
As John said in his 4.56 install writeup, it is difficult to time the gear changes and clutch releases now. I don't have the sounds that he experienced, but the car is much more sensitive to the timing of the clutch release and rolling into the throttle afterward. There is a noticeable "flare" when shifting, and it *almost* feels like it's part of the tuning of the car. John mentioned that he had previously installed the Steeda clutch spring, and I may need to do that now as well, although I had become quite accustomed to the factory clutch pedal action and had gotten the timing down for smooth shifts. I do think the two piece flywheel has something to do with it, again referencing John's experience and writeup.
Bottom line is that the car is MUCH more responsive with these gears. I'll never know what difference the new driveshaft made because I don't have the reference point of using it with the stock 3.73s, but I'm sure the two together contribute greatly to the increased response. Unless the noise gets worse, I have zero regret in this project. It will be fun the first time I hit redline once the gears are broken in.
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