So I was just messing around with this cool push button, flip up, robot like calculator today and I was checking how equivalent a rear-end gear change would be to horsepower and torque increases. As most of you know, swapping out rear-end gears doesn't add more muscle to your engine it only multiplies torque in the final output of your driveline.

On a dyno, gear swaps will not show an increase in RWHP/TQ. But I, ladies and gentlemen, have come up with a "estimate" on what the following gear changes would be like if they were calculated to how much RWHP/TQ they add.

--Do NOT pay attention to the engine flywheel #'s unless you are wondering about how much you'd lose through the drivetrain if your engine had that much power instead of modified gearing.

The following is my "estimated" RWHP/TQ #'s for a stock GT 5 speed.

- 3.27:1 260HP - 302TQ = 224.9 RWHP - 261.3 RWTQ

- 3.73:1 292HP - 339TQ = 252.8 RWHP - 293.6 RWTQ

- 3.90:1 301HP - 350TQ = 260.9 RWHP - 303.1 RWTQ

- 4.10:1 305HP - 362TQ = 269.9 RWHP - 313.5 RWTQ

- 4.30:1 322HP - 374TQ = 278.8 RWHP - 323.8 RWTQ


Try to figure out what your est. RW #'s are by adding the difference of your mods!

Hope it's useful for someone.

 

I don't get it..I know you loose power when you install certain gear ratios!

 

The only reason you loose power on a dyno is because the computer can't figure out the ratios correctly. The stock gearing with the 3.27s is 1:1 in 4th, right? If you swap gears it will change your final ratio and it is no longer 1:1 in 4th gear. So when you swap gears it will show a wrong rwhp calculation..

Gears will only make you loose power to the ground if you get a lower RING and PINION ratio than 3.27. Not sure, but I'm leaning on that.

 

rack?¿ RING!

 

you dont lose any power. its just changing the ratio in the RING AND PINION. there is no power gained no power lost. just a better machanical advantege to you.

 

yeah 4th gear stays 1 to 1. rear axle ratio has nothing to do with gear ratio of your tranny. johnson johnson. man, first figure out what you have and how it works then do some math. untill then, read a book. not trying to be mean. others would have had a field day with you.

 

Numerically higher gears, will in fact cause a LOSS of power on a dyno due to extra weight/ cent. force (ie more inertia to sap up power) these losses are minute and in no way outweigh the obvious advantages that a steeper gear can give you on the track. The torque multiplication factor is huge. For dropping ET's....steeper gears is probably the best mod for a 4.6 car.


Adam

 

I swapped out my rear for another and stepped up from the stock 3.27 to 3.90 to 4.10 all in the last month and a half. I bought a complete rear with 31 spline axles and HD traction Loc unit. I sold my old rear to a friend. Upon inspection of my old rear, we opened it and a bearing was broke in half, Luckely we found it. I dont know how long i was riding like that. I just know i wasnt putting down the rubber evenly. Fixed it and its fine now for him.

According to my Gtech performance meter ive been using. Its a window mount radar detector looking g-force meter, accelerometer. According to it. I lost 15 hp going to 4.10??? And 24hp all together over my 3.27??

I had a 3 way race today on the interstate. A nice Audi. 300hp, and a Subaru WRX, No nitrous. My bottle was empty. I stayed in 5th and kept ahead of both easily. 5th feels like a 4 1/2 gear now. We all got off the interstate and ended up all 3 at a triple lane light. The highway heated up my nittos nice. I dropped the clutch @ 4000 and surprisingly i pulled the WRX off the line. Its 4wd.

I use my Gtech meter to see if any mods add to HP, I have to have a baseline after gear changes. I give up caring about HP or wondering what my numbers are.

Id like to put some more nitrous in the motor. The zex kit i have. Its max jets are 125hp. I have old Jets from past nitrous systems. I use 52 nitrous and 38 fuel now. I have jets all the way up to 104!! 250hp jets. Ive never had one hiccup with this zex system. But i know i better not go over what jets came with it.


And 4th gear is 1to1 no matter what. same as all the other gears. Thats the ratio of the engine to driveshaft. Not Engine to Wheels. I know what you were trying to say though.

And Gears are the best Mod and bang for the buck on a 4.6. you will drop at least a half second or more in the quarter with a gear swap. Other than nitrous, nothing else for $500 or less, cept nitrous will knock the same off your quarter mile time. Of course 4.10s wont let you bury the speedo anymore. Also im not on the highway much. Im actually getting better miles per gallon. Im in 5th by 33 to 35 mph now.

 

i get way better city miles since i get up to speed faster but i hate cruising at 2500 rpms and only go 75 mph. i only picked up a tenth with my gear swap still waiting to get those drag radials. gears is a great mod.

 

But I was talking about modding my steering!
I want more power steering, lol. Yes, I meant RING sorry.

And I was just messing around I never said I was the smartest guy of the bunch, just trying to compare what it would be like with if it was HP/TQ that is gained from the gears. I figured if the gears multiply power, why not do the multiplication? Well obviously I didn't have it ALL down correctly, so when other people say "man, it's hard to explain", I'ma hearing you loud and clear now boy!

Gotchya on the 1:1 4th gearing, it's inside of the tranny and will not change. For some odd reason I was thinking 3.27 4th gear-3.27 rear gear is 1:1,
sounds dumb. But that's why I thought the gear changes made a LOSS in power when you guys said it did on the dyno. Get me?

Man, sorry you guys I feel quite stupid now.

I had never heard anyone say that they lost power with gears on a G-Tech. I bet if I would have heard that before I wouldn't have made the assumption to figure out how much power a gear swap would be equal to in terms of engine HP/TQ #'s to the ground. G-tech's are actually pretty accurate, providing you have the RIGHT information logged in.

Ok, so I don't know what I'm talking about after all, you guys are eating me alive! It's fun to be wrong sometimes! Not really.
It's all good, I'm wrong I guess. But this is how I learn, by making mistakes. Good info I have not heard before.

 

Ok, so forget about the dyno losses with the gears. That's not exactly all I was saying. A stock GT with 4.10's should run close with a 305hp/362tq GT with stock 3.27 gearing is how those #'s work BTW.

Does that sound about right or not?

 

either way you'll better your 0-60 times by putting in a better gear lol cause im only interested in my take-off (0-60)

 

You guys should read this old thread:

http://www.mustangtuningforums.com/s...ghlight=G-Tech

Blake

 

I am not sure how you came up with these numbers, but what I think you did is to do show what a gear change would equal in hp increase looking strictly at performance. In other words, adding 4:10's would be like adding 40 hp. If that is what you meant, then I think these numbers are believable.

There are drag calulators that I have used that do about the same thing. You can enter performance data about a car, and it estimates 0-60, 1/8 mile. 1/4 mile, etc.. Then you can change gears, and it gives you the new data. Then, you can look at the new data and reverse calculate how much hp it would take to get the same improvement w/o changing gears. I have done the same thing.

 

Yeah, I'm a city driver and I love the take offs. But I like watching the speedo climb more than anything when cruising along at highway speeds.

 

Hey johnson, sorry man. just used to chevy enthusiusts. have nothing against chevy just the guys that have no clue what the heck their talking about. their the ones if you say the sky is blue they say it green, or yeah like north is up and south is down. anyways, it take a bit to get used to people that admit that their off on their theory a little bit. give you props man. We are all here to learn and have fun. we dont mean to make you feel stupid.

 

Hey it's no big deal. This was the first thread I started though so I was just a little concious about it being wrong I guess. You guys know what your talking about and I try my best to get all the info I can about our cars.

MT's#1, basically the numbers I came up with just give a comparison to what gears do performance wise for us. The #s may not be exact, but it just gives you an idea of what the gears do to inhance your car's performance. I did this by giving you the multiplied torque difference between the stock 3.27's and other gear ratios to show you how much HP/TQ gains the gears can compare to, on a stock car.

 

The gtech is accurate still on the quarter mile and 0 to 60 and g's, ive noticed other people that have went up to low gears the gtech showed less Hp after putting in the vehicle weight the same. its dead on if your gears remain constant and you do other mods.

No problem being wrong and no ones flaming you, I know what you were thinking because i had it in my head like that long ago too!! My car definitly didnt lose any power. I dropped .72 seconds off my quarter according to the Gtech and thats off the juice, between my best 3.27 gear time and only 3 passes on the 4.10s And the same stretch of road and measured quarter ive used for the last 20 years!!! Also i didnt have the Upper and lower control arms on either with the 3.27s.

They every second is like another 100hp, so the gear swap im guessing is the same as adding 70+ hp on the 3.27s.


STANGER00, get those drag radials and youll pick up a half second!!! Ive never been happier that with these nitto DRs. I have 2 new tires on rims for rainey weeks, but after driving in the rain on them, the other tires on the rims werent needed. My nittos are only 245/50/16s, but its crazy how good they hook. Like i said in a different thread, I murdered a Subaru WRX AWD stoplight to stoplight a few days ago, With him spooling up harder at each light we came to. I stopped somewhere and he pulled in just to see how the hell i was pulling him off the line. I said only nitto DRs and Control arms, and 4.10s. I say "ONLY"!!!