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SPP 3.73 ring and pinion


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I'm thinking about ordering the SPP 3.73's, and wondering if anyone has installed them? Are they posi-trac? How much of a difference did you notice???

 

The parts from SPP are the ring and pinion gears only (not the differential / carrier that these bolt onto). The factory unit that came on the Shelby GTs is a limited slip unit so you would retain that if you use the original differential. 3.73:1 would not be that much of a difference than the 3.55s, but you would see a fewer RPMs higher at a given speed as compared to the 3.55s.

 

You would need to update the PCM for the speedometer to remain accurate.

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The parts from SPP are the ring and pinion gears only (not the differential / carrier that these bolt onto). The factory unit that came on the Shelby GTs is a limited slip unit so you would retain that if you use the original differential. 3.73:1 would not be that much of a difference than the 3.55s, but you would see a fewer RPMs higher at a given speed as compared to the 3.55s.

 

You would need to update the PCM for the speedometer to remain accurate.

 

 

The lower gear should produce more RPM's at a given speed...

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thanks... I think i'm going to order the 3.73's and the shorty headers. I am trying to find a good dyno shop within a reasonable distance from where i live (about an hour and a half south of buffalo or rochester, ny) so I will be able to get a good custom tune after the install. I would like to take my SGT to a Shelby authorized shop for the mods but they are all pretty far from me as much as i am aware of. Once i can get all my info together i will be pretty anxious to see what kind of gains I can get with all 3. Anyone have any suggestions or know of a good dyno shop near me??

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thanks... I think i'm going to order the 3.73's and the shorty headers. I am trying to find a good dyno shop within a reasonable distance from where i live (about an hour and a half south of buffalo or rochester, ny) so I will be able to get a good custom tune after the install. I would like to take my SGT to a Shelby authorized shop for the mods but they are all pretty far from me as much as i am aware of. Once i can get all my info together i will be pretty anxious to see what kind of gains I can get with all 3. Anyone have any suggestions or know of a good dyno shop near me??

Yes check out Kennedy's Dyno Tune. They are located in N Tonawanda. www.kennedysdynotune.com. I live near Rochester and they were recommended by someone. I have not used their services but I have spoken with the owner, Bob Kennedy and based on my conversation with him and his website he seems very knowledeable. He said he does a lot of custom tunes and he also builds race engines.

 

And at some point I will be gonig with the 3.73 gears as well as I am not in to drag racing and I have been told that 4.10s are not the right gear for road racing. I have been to watkins glen twice and I think the gear swap will give me a little more passing power.

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Yes check out Kennedy's Dyno Tune. They are located in N Tonawanda. www.kennedysdynotune.com. I live near Rochester and they were recommended by someone. I have not used their services but I have spoken with the owner, Bob Kennedy and based on my conversation with him and his website he seems very knowledeable. He said he does a lot of custom tunes and he also builds race engines.

 

And at some point I will be gonig with the 3.73 gears as well as I am not in to drag racing and I have been told that 4.10s are not the right gear for road racing. I have been to watkins glen twice and I think the gear swap will give me a little more passing power.

 

I'm interested in doing a similar set of mods (3.73's, headers, tune) but am worried about what impact it has on the factory warranty. I guess if I'm going to mod my car then I shouldn't be concerned about those things to begin with. What's your thoughts (those of you making mod's)?

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I haven't looked into the the specifics of the factory warranty. I know I should be more concerned about it but I'm not right now. I'm more worried about coming up with all the money to do what I want with my SGT.

 

I did talk to Bob Kennedy at Kennedy's dyno tune and i've figured that after everything that I want to do I'm looking at around $2000. So I prob need to wait a little longer.

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The decision to mod your SGT will always be in conflict with the factory warranty. If you upgrade your gear ratio before the end of your 3/36 or extended warranty and later suffer an HVAC problem, there should not be any problem, no conflict. However, if you have a rear end problem, say the diff clutches burn out, or, a seal pops, your dealership has a hook to hang their hat on if they don't want to make the repairs under warranty.

 

Back in the early '70s, I was a warranty auditor (factory rep) for Chevrolet. In questionable situations where serious failure may have stemmed from owner abuse/neglect (weekend racers), I would split the bill with them, buying parts or labor, which ever was cheaper for the customer. No one ever argued or complained, because the other solution was "no".

 

Seems that the major issue with dealerships and warranty work is "who did the install" and "why didn't you spend your money with us"? Most dealerships are fair and open-minded, but don't wait for a failure to find out. Go to your dealership and speak with the Service Manager. Ask him about future complications before you make the change. It is very likely that if you have the upgrade installed by his service department and top wrench, he will extend (read ignore) your upgrade should something fail down the road.

 

BTW...There is a TSB (06-19-2) on a rear end howl from the 8.8 rear end. The fix is to replace the differential clutch pack, which means that everything you would need to remove for the upgrade, is coming out. Now, ask your SM if you "make up" the difference in cash, can the wrench install the gears during the TSB repair? Be ready (and generous) to tip both the wrench and SM.

 

Happy motoring, gents.

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