Going from 3.31 to 3.73

[WildHorse]

I just picked up a spare loaded diff so I can try a different gear. Where can I get the procedure? I've done a swap in a solid axle 8.8 (foxbody), but I've heard the super 8.8 is different. I have a tool to set pinion depth on the older diff, but have no idea what the super 8.8 requires. Can you offer any assistance?

Contact @WD Pro

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[ponie1992]

Contact @WD Pro

Sent him a pm. Thanks!

 

[Mattwood440]

Yep. Can change the ratio on my device.

I have that tuner. I was told that wouldn't actually do anything. So I set the gear ratio to something absurd and drove it. There was no effect to the speedometer. I guess it's something controlled by the BCM. Livernois Motorsports wanted over $2000 to do the gears and reset the speedo. No custom tune. I got the gears done for $800 at DTS in Warren, MI. I've just lived with the error

 

[WildHorse]

I have that tuner. I was told that wouldn't actually do anything. So I set the gear ratio to something absurd and drove it.

Well you can put whatever number you want, but it'll only recognize 3.15 / 3.31 / 3.55 / 3.73. 3.73 is the max you can go. It read and wrote it & according to the fine folks at diablosport and there very user friendly updates, all's good.

Anyways for me the gears were 200. The Yukon heavy duty rebuild kit was 300. So I got 500 into it + my time haha. BTW, FORD put carbon fiber clutches in there.

 

[K4fxd]

Wild horse.

Did you reuse the shims that came out of the diff or did you have to play with shims to get the proper depth and pattern?

 

[WildHorse]

Wild horse.

Did you reuse the shims that came out of the diff or did you have to play with shims to get the proper depth and pattern?

The factory shim was bang on.

 

[K4fxd]

What brand gear did you use, Ford performance?

 

[WildHorse]

What brand gear did you use, Ford performance?

Yes Sir. Teeth depth was the exact same as the factory gears.

 

[K4fxd]

Thanks, I'm about to go 4.09. I have done many 9 inch and 8 3/4 gears but I got intimidated by the 8.8 super due to what I've read on the interwebs.

I really wish Ford stayed with the 9 inch.

 

[WildHorse]

I really wish Ford stayed with the 9 inch.

Once you dig into the super 8.8, you'll see it's much more robust, stronger & easier to work on than the Ford 9".

 

[Mattwood440]

Yep. Can change the ratio on my device.

Well you can put whatever number you want, but it'll only recognize 3.15 / 3.31 / 3.55 / 3.73. 3.73 is the max you can go. It read and wrote it & according to the fine folks at diablosport and there very user friendly updates, all's good.

Anyways for me the gears were 200. The Yukon heavy duty rebuild kit was 300. So I got 500 into it + my time haha. BTW, FORD put carbon fiber clutches in there.

I forgot cuz it's been 2 years, but the thread below describes how it works with the gear changes. Changing the gear does nothing with the speedometer. I have a manual so no other changes were necessary. I'm not sure why the rep at Livernois either didn't know that or was trying to rip me off. If it's an auto, the BCM needs to be changed via Forscan, etc. due to shift points. Diablosport tuners won't do that. My current speedo error is caused by going back and forth between different sized summer and winter tires and just being lazy

https://www.mustang6g.com/forums/threads/speedometer-calibration.110607/post-2392922

 

[WildHorse]

Diablosport tuners won't do that.

For me changing the tire size works very well, plus I know the gear ratio change doesn't affect the speedometer. So why is there the option for the gear ratio then ?

 

[K4fxd]

The S550 uses the BCM and the ECM to decide what gear and tire size are on the car. If you are 3.73 or below (manual) (3.55 auto)and within 20% of a stock tire size, the car will automatically figure out the gearing and the speedo will be correct.

If say you want a 3.91 or 4.09 or 5.13 you need a tuner to change the max ratio in the ECM portion of the tune.

Forscan will not change this value.

 

[WildHorse]

If you are 3.73 or below (manual) (3.55 auto)and within 20% of a stock tire size, the car will automatically figure out the gearing and the speedo will be correct

Well guess I'm good then. 3.73 and 28" Mickey T's.

 

[K4fxd]

Yep, you should be fine. But I would verify by GPS or stationary radar.

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