Gear Swap

[trplblk96gt]

It looks like I'm going to have to do a gear swap in the very near future and I'm going with a 3.73. I have a couple of questions though...

1) I have a 96 Gt, will I need a speedo recalibration tool or a new speedo gear to correct the speed change?

2) I'm considering getting new axles as well, how can I find out if I have a 28 or 31 spline differential without opening the rear end?


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[Ferocious]

It looks like I'm going to have to do a gear swap in the very near future and I'm going with a 3.73. I have a couple of questions though...

1) I have a 96 Gt, will I need a speedo recalibration tool or a new speedo gear to correct the speed change?

You will need a speedo re-calibrator. The new speedo get will help your speedometer a bit, but will not be completely accurate.

2) I'm considering getting new axles as well, how can I find out if I have a 28 or 31 spline differential without opening the rear end?

Our cars come with 28 spline stock i believe. Has your rear end been rebuilt by the previous owner already?

 

[trplblk96gt]

No the rear end hasn't been touched. Any recommendations for the calibration tool?


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[joekd]

1: get the ford motorsport speed dial calibrator, I cannot stress enough to stay away from the dallasmustang speedcal and have a thread here explaining why

2: as mentioned you will have 28 spline unless someone already worked on the rear end, if they did then I would hope you dont have OEM gears in there

 

[1997GT4.6]

FRPP speed dial. It's the best one and easy to install. Don't use the speed gear, they tend to still be a little bit off. My car is dead on with the speed cal. You don't need to uprade to 31 spline unless you are going to be doing some serious drag racing. Or at least I wouldn't for a street driven car that doesn't see racing at the strip with slicks and skinnies.

Don't fear the gear!! 4.10's FTMW!

 

[trplblk96gt]

Don't fear the gear!! 4.10's FTMW!

I definitely have a desire to get 4.10s in the back of my head that keeps nagging at me but I'm nervous that going with that big of a gear will murder my gas mileage.


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[joekd]

Do you do a lot of highway driving? My overall MPG is pretty much identical with 4.10's to how it was with OEM gears, most of my driving is around town though.

I am still only ~2.5K rpm at 75MPH

 

[trplblk96gt]

It just depends on how I feel in the moment - interstate or back roads. I'd say it's about 50/50ish


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[joekd]

Honestly consider 4.10's, they aren't nearly as bad as you may think RPM wise but the extra performance is worth it

 

[Gallows]

1: get the ford motorsport speed dial calibrator, I cannot stress enough to stay away from the dallasmustang speedcal and have a thread here explaining why

My DM unit works fine although it is a older unit. Where is your thread?

As for gears 4:10's would be the minimum that I would do in a N/A car and they worked well in my 97 when it was S/C. I went to 4:56's with my IRS swap and there isn't a whole lot of difference so as they say "Don't fear the gear".

 

[trplblk96gt]

Ok so I'm pretty sure I'm going to go ahead and pull the trigger on the 4.10s. I would hate to buy the 3.73s and then wish I had gone bigger. I've also decided that since my car is so old, and to the best of my knowledge hasn't had any upgraded rear end work, that I'm going to overhaul the whole thing. This is everything that I'm looking at buying...

Ring and Pinion:
http://www.mustangsunlimited.com/it...on&SubSubCategory=Gear+Sets/Kits&CatKey=74-01

Install Kit:
http://www.cjponyparts.com/ford-racing-ring-and-pinion-install-kit-supreme-8-8-1985-2012/p/M4210C/

Trac-LOK Rebuild Kit:
http://www.americanmuscle.com/ford-88-traclok-kit.html

Speedo Calibrator:
http://www.americanmuscle.com/ford-speedo-tool-9410.html


The last thing I need help with is the fluid. I know I'm getting Royal Purple, but which would be better? 75w90 or 75w140?


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[joekd]

Pretty much identical to the parts I used on my rear end, ford has the gears cheaper then that http://www.buyfordracing.com/products/8.8--4.10-RING-GEAR-AND-PINION-SETS.html

Sn95's use 75w90, I also used Royal Purple

You will still need to pick up one bottle of friction modifier to soak the clutch packs in before install

 

[Venom351R]

I used to fear the gear until I took the plunge and got 4.10's and they are awesome, Id never go lower for the set up I have now. I dont care about my gas mileage so that was not a factor for me.

 

[Ferocious]

2 quarts of royal purple 75w90 gear oil & 1 bottle of friction modifier and youre golden.

 

[trplblk96gt]

Pretty much identical to the parts I used on my rear end, ford has the gears cheaper then that http://www.buyfordracing.com/products/8.8--4.10-RING-GEAR-AND-PINION-SETS.html

Sn95's use 75w90, I also used Royal Purple

You will still need to pick up one bottle of friction modifier to soak the clutch packs in before install

Thanks man!

So do I need a bottle of friction modifier to soak the clutch packs in and a bottle for the gear installation too?

 

[Ferocious]

So do I need a bottle of friction modifier to soak the clutch packs in and a bottle for the gear installation too?

Yessir..

I think CJPP has the best price on it.
http://www.cjponyparts.com/ford-rac...ch-type-limited-slip-differentials/p/M19546A/

 

[jo4roush99]

I am still only ~2.5K rpm at 75MPH

Are you sure? My 96 GT with 4.10's w/275/40/17's ran 2900 rpm @ 75 mph.
My Cobra with 3.73's runs 2400rpm's @ 75mph.

 

[joekd]

Sorry typo, ~2.8K RPM @ 75

 

[trplblk96gt]

Is that not kinda high RPM to run for an extended amount of time?

 

[twovalveterror]

it is *slightly* high, in my book at least. I run 3.73s for that reason. I run on the highway way too much to justify any more than that. it's all about how you're going to drive it. I may switch to 4.10s or 4.30s with my new set up though.

in comparison, my csvt runs at 3k at 70 mph. I have heard talk that it's because the ohc needs higher rpm to oil the top end efficiently. I took that as engineer speak for "we put that high gear in it so the car didn't feel like a complete turd."