Vince95

Foremention :
I've had my 95 Red/Black SC3 5Spd with 130k for now three months, bought it as a second commuter car for work. Fomerly onwed by a woman nurse. Love the car and have only a few intentions with regards to mods. If there were to be a quirk i do not like is not having a decent cruising RPM. I acrue mostly highway miles 40+ each day and 70-75 mph winds up to nearly three grand on the tach. I'm not out for warp speed 0-60, just a nice hum down the highway as I like to tour the state by road most weekends.
My question: (Don't hate for intentionally wanting to slow my) Has anyone swapped the rear diff in your five speed for the 3.26 R/P instead of my 4.08. Or how abou the 3.92 ? This seems like the next alternative to a Getrag 6sp swap which is very expensive not to mention hard to find. I realize evrything will need recalibration but think that 2400-2600 revs at 70 would be worth it, and still be in a decent portion of the torque curve. Let me know what you all think.

Thanks,
Vince
- - - Bleed Toyota - - -


95 SC3 5spd Red/ Black
2003 Maxima 6spd Black/Black
2000 Z71 Tahoe Pewter/Charcoal

vipsoarer

the difference is going to be very small and wont change much with the 3.92. Just keep in mind that 3.26 you will be noticeably slower through all gears by changing the rear end to a lower gearing. so if you think the sc is slow stock, it will be even more so with the 3.26.

95 Integra

BTW, gas mileage wont be effected at all (or if so, every so slightly negatively), so I'd say get use to the higher rpms or sell off the sc3 5spd and get a newer 98+ sc4 auto (290hp, 5spd auto, its faster and a nicer driver for beating around like you're doing). BTW, my integra was kicking out at 4400 rpms at 80mph....woot woot.

SPORTcoupe

iTrader: (2)

It's actually even cheaper and easier than swapping out the whole diff. Find a busted donor diff and take the 2 to you local differential shop. They can swap the gear for you for a minimal charge. They are directly interchangeable with the Auto TT diff gears(3.26). While you're in there, opt for new bearings.

Cheers,
~Alan

Bean

iTrader: (1)

Auto TT doesnt have 3.26 gears... I'm assuming you're talking about a SupraTT, its like 3.7 something. Manual rear is 3.13

Not exactly easy to find a busted diff from one of these cars either

95 Integra

SC300 5spd - 4.083
SC300 auto - 3.92
98+ SC400 5spd auto - 3.266

Supra NA - 4.272
Supra TT auto - 3.769
Supra 6spd - 3.133 (FD will not swap into any other casing)

BTW, the TT auto would probably be the best of both worlds for Vince95 (though I'll just keep my 4.08s personally).

Project300

Gas mileage certainly will be effected and it will be positive, not negative.

Even the smallest change from 4.08 to 3.92 is a 4% increase in mileage, which will get you about one more mile per gallon. 3k on the tach would be 2880. The 4.08 to 3.266 would get you a 25% increase, which is huge. You would get about 5 more miles to a gallon and the tach would drop to 2400. Even mounting larger diameter tires could give you another mile per gallon and about 100 rpm less on the tach.

As mentioned, all these would make the car accelerate slower but they also could increase the top speed.

BTW, this isn't an Integra forum.

SPORTcoupe

iTrader: (2)

It's not quite that simple/linear.
Our engines were designed for peak efficiency at typical highway cruising speeds and therefore typical crusing RPM.
If you put in a lower ratio rear end, you will be dropping out of that range.
You may not really think about it, but a certain amount of torque is required to keep your car moving at the same speed on the freeway. When you reduce the ratio, the torque drops (very slightly of course). Now in order to maintain the same speed on the highway, you have to press slightly more on the gas. This opens up the throttle plate a bit more and lets in more air, and for more air, you need more fuel. Your fuel savings from lower RPM have just been negated.

As for the larger tires: they create more drag and therefore reduce gas mileage. Only thing larger tires are good for is throwing off your speedo and making the odometer read less than the mileage you actually put on the car.

~Alan

UpInTheLex

iTrader: (5)

3000 rpm is a good rpm for getting up on the torque curve, making it easier to accelerate. I know the 1uz-ve V8 doesn't make much power until about 2800rpm. If you were only reving 2300 or so you'd have to spend a lot more energy trying to accelerate because you'd be off of the torque curve. More throttle %, more fuel being burned.

I'm trying backing up what SPORTcoupe said in a different way, although he couldn't have said it better.

Project300

SPORTcoupe had some true words. I agree, mostly.

As we all know (and Vince95 pointed out), the SC is a nice a way to get from city to city when you don't have lots of passengers, but the mileage sucks and the engine spins. Yet, the car is in it's element on the open highway. That's an understatement. So this thread is long overdue.

There will always be factors that could effect the final drive ratio. For instance, you could conceivably change the final drive ratio while also adjusting the programmed engine valve timing to bring the power band further down. Viva VVT-i! This could be engaged (by programming the ECU) electronically only over 60mph so driveability in town would not change. It would sip gas and have no torque above 60, but the power would be at it's peak for cruising steady and efficient at 75+.

Tire diameter and gear ratio are close enough to be considered equal when trying to reduce curuising rpm's.

Roll on the miles.

Cannonbear

vvti is always on through out the powerband. you really cant tell it to turn on at a set speed or rpm. it doesnt quite work like other variable valve timing.

Bean

iTrader: (1)

That is incorrect about the Supra 6-speed. The USDM market Supra has a 3.133 rear end. you are quoting the ratio for the JDM supra. Good info otherwise

95 Integra

Indeed you are correct. BTW, anybody that says lower gearing = better gas mileage most likely needs to do some research on the effects of gearing as a torque multiplier and BSFC (brake specific fuel consumption). You'll quickly find that it takes the same amount of overall torque to push the car at 70mph and that you are now playing on the motors efficiency to provide gas mileage. With that being said, whether you run a 1:1 gear ratio and make the engine produce 200 ft/lbs of torque at 1000rpms to push the car (200 ft/lbs at the wheels) or run a 3:1 gear ratio and only require the engine to make 67 ft/lbs of torque at 3000 rpms (200 ft/lbs at the wheels) the actual fuel consumption isnt going to vary much. Then factor in BSFC which states where the engines most efficient point lays and you'll soon realize that you'll get slightly better fuel economy at 3k.

Bean

iTrader: (1)

Sorry; but it doesnt have anything to do with acceleration unless it is all stop and go traffic. Most driving is done at cruising speeds; especially highway driving. Taller gear = lower cruise rpms = better gas mileage. Its well known and its a proven fact. Looking good on paper doesnt always equate to being correct. Its at such low loads anyways that BSFC doesnt play much of a factor at all. (when cruising anyway).

Its why LS1 cars get such great gas mileage on the highway, that ultra-low 6th speed (like a .54) helps a lot on a car with a stock 2.73 or 3.23 rear end. Its another reason why current Toyota offerings are getting such great gas mileage... they have a low 6th gear which improves fuel economy drastically vs a 5-speed or 4-speed.

Most places people live are not all city blocks. I live in a city where its long roads with occaissional traffic lights (too many on some roads) but its still long drives. Lower gear ratios here makes a big difference.

SPORTcoupe

iTrader: (2)

No idea what you just said.