What do I need to order for a rear gear swap?

robster94gt

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Hey all,
I'm going to order parts to swap gears in my 94gt. What all should I order? Ring and pinion, and 'install kit'?
There's a Ford Performance Gear and Install kit on American Muscle - would that be everything I need?

Screenshot 2024-04-11 212948.pngThanks,
Rob
 

96blak54

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What gear are you wanting to swap in?

Good idea to stay with a FoMoCo gear set. And Wmac has a good idea to replace the axle bearings and seals while you are at it. May as well rebuild the entire rearend along with that kit. Will you be performing the swap yourself or having someone else do the work?
 

Mustang5L5

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A new rear diff cover if you can swing it the non-critical expense. I dislike refilling the differential from the factory fill hole.
 
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robster94gt

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Thanks for responses so far guys - So I'm looking to put in 3.73s. There's a place here that I think knows what they're doing. We don't have much in the way of shops that are experienced with Mustangs.
I'll look up the bearings and axle seals - would that add a lot of extra labour?
 
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robster94gt

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Oh, And I'll need to recalibrate the speedometer. Do you know which parts I'll need?
 

badass98svt

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Thanks for responses so far guys - So I'm looking to put in 3.73s. There's a place here that I think knows what they're doing. We don't have much in the way of shops that are experienced with Mustangs.
I'll look up the bearings and axle seals - would that add a lot of extra labour?

They don't need to be experienced with mustangs necessarily. The same 8.8 is in many other Ford vehicles.
 
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robster94gt

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I've read conflicting information on what plastic gears will work in the transmission, and give accurate speedometer readings and not chew up the gears. Do you guys have any info?
Thanks,
Rob
 

Wmac

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A 23 tooth (white) is the largest tooth count available. It works with 3.55 gears. Nothing else out there for 3.73 and up. So your speedo would be off (high?) and the only way to correct it is with a calibrator. Or use a gps with your phone? Or change the drive gear on the trans main shaft if T5.

I had used a Ford Racing "speed dial"with my AODE trans, 4.10 gear and 23 tooth. It worked fine. Just recently did a T5 swap so installed a 6 tooth black drive gear.
 
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robster94gt

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A 23 tooth (white) is the largest tooth count available. It works with 3.55 gears. Nothing else out there for 3.73 and up. So your speedo would be off (high?) and the only way to correct it is with a calibrator. Or use a gps with your phone? Or change the drive gear on the trans main shaft if T5.

I had used a Ford Racing "speed dial"with my AODE trans, 4.10 gear and 23 tooth. It worked fine. Just recently did a T5 swap so installed a 6 tooth black drive gear.
Oh, that's unfortunate- how do you recalibrate? And for the phone, GPS- do mean just use that for speedo?
 

Wmac

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A 21 tooth driven and 7 tooth drive will be correct for 3.73 gear ratio, but all T5's after 1990, all T45 and all automatics have an 8 tooth drive gear.

See this info:20230321_154444.jpg
 

joemomma

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Without changing the gear on the transmission shaft, the speedo gear won't last more than two weeks. They just get chewed up because the finer teeth don't mesh well. The best solution is an Abbott ERA - mine is spot on once I got the correction factor dialed in. I've got install details in my build thread.
 

Daryl

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Nobody takes the tail housing off the trans to change the tail shaft gear so it’s never correct above 3.55’s
There’s definitely truth there. I swapped the plastic tranny gears a few times and the speedo was still never 100% accurate. Best is 2-3mph off. So, to get my true/actual speed I use the Speedometer app on my iPhone and adjust accordingly.image.jpg
 

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