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03 GT Getting Rearend Rebuild - Good Gears????

1K views 16 replies 6 participants last post by  AnthonyG1562 
#1 ·
Hello All,

I am having my rear end rebuilt on my 03 GT 5sp with 116,000 miles and am going from the stock 3.27 gear to a 3.73 gear with the full install kit and clutch packs. My question is, what are some good brands? The shop that is doing the work is building an estimate now and I want to know the brand prior to them ordering so I can confirm they won't be whining or low quality. What are some companies that make quality, quite 3.73 gears? I don't have the cash to afford another rebuild in the near future and don't have the skills to do it myself so I want to make sure it's done with quality parts. Also, what kind of warranty should I push for? This shop doesn't seem to thrilled on a giving a warranty on a rear end for a sports car.

Thank you everyone for your help!
 
#2 ·
Get the Ford Racing kit from American Muscle. Also get 4.10s. The 4.6L needs more help down low and the 02-04 GTs have a deeper overdrive gear so its not too much for the highway.
 
#3 ·
Thank you for the input. I did strongly consider the 4.10 and was originally going to go with them but the more I researched the more I realized 3.73 might be best for what I plan on doing with the car. For me, this car is mint, I mean underneath and under hood, zero rust, dings, scratch, or even cracks in the leather seats. I am going to 75% cruise, 25% get on it. My 93 GT had a 4.10 and for cruising, I had to shift at 3000 to keep up with traffic and its a lot of shifting for around town. Since this isn't just a car to race and will be doing more cruising than racing, do you still think the 4.10 is a good choice?
 
#4 ·
Thank you for the input. I did strongly consider the 4.10 and was originally going to go with them but the more I researched the more I realized 3.73 might be best for what I plan on doing with the car. For me, this car is mint, I mean underneath and under hood, zero rust, dings, scratch, or even cracks in the leather seats. I am going to 75% cruise, 25% get on it. My 93 GT had a 4.10 and for cruising, I had to shift at 3000 to keep up with traffic and its a lot of shifting for around town. Since this isn't just a car to race and will be doing more cruising than racing, do you still think the 4.10 is a good choice?
Your 93 had a .68 overdrive, your current car has a .62. It would be similar to having 3.73s in your 93.

The difference between 4.10s and 3.73s is not as drastic as many would lead you to believe.

But if you are going to be doing mostly highway I'd get 3.55s or just leave it at 3.27. If you do plan on getting on it at all tho you will want 4.10s. Hell I was going to get 4.30s for my last NA 4.6L...


You can also jump up the tire size out back too if you feel your RPM are still too high. I ran a full inch taller than stock spec out back on my last car. Plenty of room.
 
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#5 · (Edited)
I just got 3.73 gears installed yesterday but i haven t driven it enough to see all the excitment lol

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#6 ·
Definitely stay FRPP with everything you get. Not sure if the kits come with bearings but at 116k miles I would strongly recommend replacing them too.

Also, any shop that isn't willing to warranty their work would have me questioning whether I should take my car there. I see you're in Belvidere, that's not that far from Milwaukee. I'd highly recommend Marv at C&M Automotive Performance. He did my 4.10's and 31 spline upgrade. He uses all FRPP products and guarantees his work.

I have not been nice to my rear since the upgrade, and I've had zero issues, whining, grinding or anything.

C & M Automotive Performance
 
#7 ·
I got 4.10 in my 2004 GT. Ford racing gear set and the install kit from American muscle. Performance is pretty insane compared to the factory 3.27 gears. At 70mph the motor is turning about 2350rpm and with my race tune I'm still getting about 21mpg.

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#8 ·
sonicpony03 - Thanks for your feedback! I am doing the full install kit with clutch packs because I don't want to deal with this rear end in the near future. I took the car in because it was making a whom whom whom. The tech should know since that is why I took the car in I don't want any noisy gears. Plus, I called the shop before they ordered the parts and wanted to make sure they weren't going to throw the cheapest parts in there and that I would pay extra for quality parts so hopefully their good an quite.
 
#9 ·
sonicpony03 - Also, the shop the car is at, the tech I talked to who does their rear end rebuilds has an 01 with 800HP and said he has changed the rear end multiple times. The owner confirmed the story when I dropped off the car and also added the techs brother has a 11 second Z28. The fact that the tech who is doing the work has done this job on the same car makes me think it will get done correctly and also, he should know good gears.....I hope.
 
#10 ·
Well hopefully they do it right then... Still say you should be doing 4.10s but its obviously your car.
 
#11 ·
Well it sounds like you have confidence in them. I am the type that puts confidence in a written and signed document over someone's word but to each his own. Also I've found that just because someone has a fast car doesn't always mean they know what they are doing. Fingers crossed they are legit and aren't blowing smoke.

I second the 4.10's...don't fear the gear! But again it's your car and if you feel you'll be happier with the 3.73's then go for it.
 
#15 ·
So..Got Car back....

Shop called and said car was finished with a but...the clutch packs they received were upgraded clutch packs with an extra clutch plate or shim, not exactly sure what made it different than normal, but tech said the rear end was very tight and when you turn the when as much as you can at and turn at a slow speed the wheel hops. He said the it may loosen up or I can come back and have it adjusted. Does this sound normal???
 
#16 ·
Adding an extra clutch is actually an upgrade you can do to a stock diff. Normal. Have them set it up how you like it.

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