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5th gear

9883 Views 75 Replies 13 Participants Last post by  thedrumm
Is there a taller 5th gear out there for us? I run 70mph on the interstate & that is 3000 rpm. If I had a taller 5th gear, I could run 2000 rpm & save a ton of gas.

I also searched for a swap with the 6 spd Tib box, but found nothing.

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Larger diameter tire. 205/60/15 on stock wheels or a 205/55/16 on 16" wheels. Adds abuot 5%-ish to the od of the tire. This DOES make the speedo read 5% too slow, but if you can do a little math in your head you can always be right on. Any bigger (had 205/60/16 for a week) and you're affecting the final drive too much in the wrong direction.
You'd have to disassemble both trans and HOPE it was made the same internally. Just because a company makes trans for multiple car makers does NOT make them interchangeable.

Again. . . buy a larger OD tire and be done.
Outside Diameter. . . taller tire. Bigger than the 195/60's on the car.
It looks like OD tires for me. I figured I would not be able to find a taller 5th gear, but it was worth a try. I drive all most all interstate, so I was looking for better gas mileage in any way I could get it. Especially since I am keeping this until it dies, which hopefully will be 12 more years.

Thanks for the input!
I have the same type of drive. I65, 865, 465 to keystone and two stoplights later I'm at work. That's why I went with teh 205/55's instead of the "correct height" 205/50 16's long ago. I keep in mind that an indicated 65 is closer to 70 ground speed and back off a little and get (got, having new issues)great gas mileage on my non-CVVT Beta.
LOL of course they can be unique, why not?

It was a huge hinderance in WWI when we had trucks from, what, 150 manufacturers? Spare parts logistics was a nightmare because they don't HAVE to be the same without a standard.
While that's intersting info and stuff, it has no relevance here. Hyundai used a different wiring harness for GLS, GT, Limited, auto and manuals. . .A different wiring harness for each model and type. That's a sure sign of stupidity on their part. What about SPIII fluids only?

Go to a taller tire and be done.
Been running 4% larger tires for 5 years. No one has thought the car looked goofy yet.
But its not really doing you any good for this purpose.

Id rather have an accurate speedo anyways.
Really? And what do you base your theory on? I run slower than indicated than I am actually traveling. That means lower engine rpms. Lower engine rpms at speed means less fuel wasted. I can run 70mph indicated and stay with traffic. When I ran the 'kooks which were 1% smaller than oem I had to run 75mph indicated to keep up with traffic. 75mph=3200rpms for me. 70mph -2900/3000rpms.
195/60/15 tires and stock trans = 70mph is calculated to 2980rpm
205/55/16 tires and stock trans = 70mph is calculated to 2900rpm

2.7% difference. not much to write home about guys.
Actual measurements of the tires puts it a 3.8% as each tire is a little different in it's actual physical dimensions. But hey, you're right. What could I POSSIBLY know about ANYTHING. You, sir, must be God.
ALSO. . . keep in mind you can go TOO far. When I had the 206/60's for 2 weeks, my mileage actually dropped a little because the engine was lugging too much up hills at highway speeds. It's a fine balance that can quickly be pushed too far.

I stand by my opinion on leaving the trans the F alone.
2 tanks(AND A HALF), and 205/60/16's measured out to almost 7% difference in overall height. And yes, changing the final drive almost 7% does make a difference. The steeper hills almost needed a downshift at 65.

We ran a full tank out by the time we got it home the first day. Ran 2 more full tanks and a half tank.
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