3.73s worth it?

[dazed1]

My 07 gt came with 3.55s from the factory and I think its a great overall gear. I dont want to have to shift too soon and lose top speed (although its not like I top it out) and would like a bit more acceleration. Im thinking 4.10s would be too much for what Im after but 3.73s are too close to 3.55s to feel much of a difference. Thoughts?

3.73 can standard in my 2009 Bullitt and still being NA with some bolt on's I have been perfectly happy with them.

 

[pwd72s]

3.73 can standard in my 2009 Bullitt and still being NA with some bolt on's I have been perfectly happy with them.

I can say the same here...but I don't go to the strip, so couldn't care less about 1/4 or 1/8 mile times. 3.73 works fine for the twisty back roads here. Yet I don't feel like I'm revving the engine to death when doing 80 or so on the interstate. All depends on what you use your car for.

Too bad we have a nation between us...I'd let you drive my '09 Bullitt so you could watch the tach at various speeds.

 

[ox white]

3.73 on a NA 3V daily driver is just about perfect IMO.

 

[redfirepearlgt]

Don't fear the gear. If you take the gear ratio of 5th gear in the Tremec 3650 and do the actual calculation, you will find that at 2500 RPM with a 4.10 gear on a 26" tire (stock dia. on 99-04 GT)the car will be running 69 MPH. With a 27" tire (stock dia. on 05-09GT) the car will be running 72MPH.

With a 27" tire a 3.73 gear will run 80mph @ 2530 RPM. With a 4.10 gear the same car will run 2780 RPM at 80 MPH. This is in 5th gear with a 0.68 OD gear in a Tremec 3650.

It boils down to whether or not you feel an increase of 250 RPM is too much RPM on the engine at cruising speed or you actually want to enjoy feeling it in the seat of your pants. You won't be the first person wishing you had gone 4.10's if you go anything taller.

 

[07 Boss]

I'm a fan of Richmond as well. I would have done a set of 3.90's myself, but a buddy gave me a brand new set of FRPP 3.73's he had bought and went another route with his build. The 3.73's and D1SC were beautiful together on the street.

As far as setup, I usually do my own gears. The hard part for me is that damn crush sleeve. I really hate having to take the diff back out. It's a PITA! lol

Richmond also make a crush sleeve eliminator for the 8.8". I believe it is just a solid spacer but it supposed to make setting the pinion easier by not having to worry about ruining the sleeve.

 

[ChewyR]

Having had all three sets 3.55, 3.73, and 4.10 my experience has been NA 4.10, will really make the 3v feel quick. 450 rwhp go with 3.73, fun car. 550+ 3.55 especially if its via TVS or twin screw, need to let the torque/area under the curve do its thing.

 

[Pentalab]

Don't fear the gear. If you take the gear ratio of 5th gear in the Tremec 3650 and do the actual calculation, you will find that at 2500 RPM with a 4.10 gear on a 26" tire (stock dia. on 99-04 GT)the car will be running 69 MPH. With a 27" tire (stock dia. on 05-09GT) the car will be running 72MPH.

With a 27" tire a 3.73 gear will run 80mph @ 2530 RPM. With a 4.10 gear the same car will run 2780 RPM at 80 MPH. This is in 5th gear with a 0.68 OD gear in a Tremec 3650.

It boils down to whether or not you feel an increase of 250 RPM is too much RPM on the engine at cruising speed or you actually want to enjoy feeling it in the seat of your pants. You won't be the first person wishing you had gone 4.10's if you go anything taller.

On my 2010 auto and oem 3.31 rear gear..and 27.2" tall tire it's 2100 rpm @ 70 mph in OD. With a 4.10 rear gear, it would be 2601 rpm. On the 5r55s auto, 2nd gear is 14% lower than the Tremec 3650..and 16.5% lower in 3rd gear. In 4th gear they are both 1.1
You would require a 3.73 with a 3650 to equal the 3.31 in 2nd gear on the auto. You require a 3.90 with a 3650 to equal the 3.31 when in 3rd gear on the auto. 1st + OD are geared higher in the 3650. I wanted a good pull in 2nd and 3rd gear for street and hwy use, so left the oem 3.31 rear gear alone. As is, it's barely 93 mph in 3rd....and 62 mph in 2nd....at 6 krpm... which is where my auto shift points are set at in the tune. Where I lose it is when in 4th gear...so it's a trade off. With the 3.31 and in 4th gear, it's 2 krpm @ 50 mph, 4 krpm @ 100 mph..and 6 krpm @ 150 mph.

 

[eighty6gt]

3.73 in a 500+ hp Bullitt have been great. The trans is the problem, 3rd is too tall.

Going to try them with the T56. Probably also good.

 

[702GT]

Richmond also make a crush sleeve eliminator for the 8.8". I believe it is just a solid spacer but it supposed to make setting the pinion easier by not having to worry about ruining the sleeve.

Now we're getting into diff theory. In drag racing, it's possible you could further crush the crush sleeve in the 8.8 via hard enough launch, which could cause catastrophic failure. The solid spacer does negate that possibility, however could also make the diff clunkier. Also you're stuck with whatever pinion depth the spacer sets you too. There are advantages to being able to favor a pinion depth. Ultimately as long as the spacer puts you in spec, the diff will perform properly. I do like the solid spacers, but as a street car there was never a need for it. I only over-crushed a sleeve once, and after that was careful never to do it again LOL. Taking the diff back out sucks when you're doing it in the garage floor!

Looking into doing gears in my F250 (3.31 to 3.73) but maaaaan. Think my driveline shop is gonna do this set. 4x4 and all.

 

[cavero]

Wow I did not expect this much input thanks guys. It looks like 4.10s are in my future! I just paid the car off but Id like to save up for a while before I do anything so its staying na for a while anyway.

Swflastang, that sounds good to me!

My 3.55's developed a whine that was driving me crazy so I went to 3.73's as an upgrade since I was going to be getting new gears anyway. But like other's have said, it made a difference but not night and day. You could feel it but it wasn't like "Oh damn". I probably wouldn't spend the money going from 3.55s-->3.73s unless something was wrong w/ the old gears. Even on the highway my RPM only went up by 200 and my gas milage didn't take any hit.

 

[travelers]

If you set the pinion up with the correct pre-load, all you have to do is remove the crush sleeve and measure it and either pick up a kit or have one made to that measurement and reinstall.

 

[JBert]

I know I'm late (frequent flyer on other forums but not here) but I really don't understand the obsession with short gearing. I guess if you are building a drag car and trying to optimize shift points then they might be helpful. But for a street car they just make you have to shift a lot quicker and first gear becomes practically useless, so you have a 4-speed for practical purposes. My advice to the OP would be to stay with the 3.55 unless you have some specific reason you want to change the final drive ratios.

 

[stkjock]

I know I'm late (frequent flyer on other forums but not here) but I really don't understand the obsession with short gearing. I guess if you are building a drag car and trying to optimize shift points then they might be helpful. But for a street car they just make you have to shift a lot quicker and first gear becomes practically useless, so you have a 4-speed for practical purposes. My advice to the OP would be to stay with the 3.55 unless you have some specific reason you want to change the final drive ratios.

spoken like one who's not had 4.10s in a 3V S197

12 years of history show 4.10s are a perfect choice for these cars either N/A or centri blower - twin screw is a different discussion.


" shift a lot quicker" also a farce in my view, the difference (with stock height tire) from 3.55s to 4.10s in MPH at 3000 rpm is 3 mph, so you shift 1-2 at 17 mph instead of 20 mph... really, that's "a lot quicker"???

4.10s make the car a lot more responsive off the line and while in gear

 

[fdjizm]

Fo tens fo sho!
I am actually on 4.30's now due to the trans swap

Stkjock <3 miss ya bro!

 

[redfirepearlgt]

 

[stkjock]

Stkjock <3 miss ya bro!

so come around more brah!

/\ QFT

 

[06 T-RED S/C GT]

spoken like one who's not had 4.10s in a 3V S197

12 years of history show 4.10s are a perfect choice for these cars either N/A or centri blower - twin screw is a different discussion.


" shift a lot quicker" also a farce in my view, the difference (with stock height tire) from 3.55s to 4.10s in MPH at 3000 rpm is 3 mph, so you shift 1-2 at 17 mph instead of 20 mph... really, that's "a lot quicker"???

4.10s make the car a lot more responsive off the line and while in gear

With N/A and centri blowers, I totally agree that 4:10s are the perfect choice for the S197 3V. However with the twin screw Saleen VI I've been running, 4:10's appear to be a bit too short on the top end and therefore I'm looking into having the stock 3:55s put back in. I'm also running stock tire height at 27' with 285/40/18's rear and running 425 RWHP between 7.5 -8.0 psi boost. So my question is this, would it be in the best interest for my particular application to put the stock 3:55s back in or purchase 3:73's instead?

 

[stkjock]

my .02 - go to a 28" tall tire first, if they don't work well you can always change out the rear end, sell the 28"s

simpler and cheaper, also likely a good solution.

 

[06 T-RED S/C GT]

Prior to switching to OEM Shelby GT500 rims in 18x9.5" I had been running Steeda Spyder 20x9.5" rims on Nitto 555 G2's in 275/35/20 which are 27.6" in diameter. Although they're just slightly shorter, they were as close to 28" diameter as I could get without rubbing the inner fender up front, as I run the same size tires in a square setup. After checking both tire rack and discount tire, the closest tires I could find in 18" sizes were Conti sport contact2 in 275/45/18 with 27.7" diameter and Bridgestone Potenza RE050 also in 275/45/18 with a 27.8" diameter. If 275/45/18's will clear the front inner fenders without any rubbing? then I'll go that route, however, if they won't clear up in the front? then it looks as though I'll have no other option, but to have my stock 3:55 ring and pinion gears put back in

 

[Sactown]

5.85's or get the fuck out!