8 replies to this topic

[timmib]

Know this is kinda off the wall but is there a way to reduce the rpm's at highway speeds with a 5 speed awd?

We take a long trip (2400 miles round trip) once and sometimes twice a year. The engine runs at 3600 to 3900 rpm for hours at a time frequently. Can't say I've seen any undo effect to the engine. But, it seems strong enough that it could cruise easily at, say, 3000 rpm.

TIA

Be well,

[CoupedUpSubie]

I am assuming it is a Legacy Outback. Based on the gear ratios of your transmission you have 3 options.

Don't drive 80 mph all the time.

Or

Put 32 inch tires on your car.

Or

Swap in a transmission from 99 Legacy or anything with the same transmission.

[nickb21]

Yea, not sure there are a whole lot of options available to you. The 4 speed auto's are geared slightly differently and rev about 500rpm or so lower at similiar speeds.

I believe you can swap the 6-speed in, but between the amount of work/$$ it would hardly be worth it - I don't know what the final drive would be in 6th, might not even rev much lower. Maybe you could crack the trans case and do some type of gear fabrication, but that is tons of work as well.

What is your main reason to get the revs down; noise, mpg?

[WoodsWagon]

You can change out 5th gear and you may be able to do it with just removing the transfer housing from the transmission in car. The GT's came with a .78 overdrive while your outback has a .82 overdrive, so 5th out of a GT would drop your cruising RPM's a fair bit.

Easiest would be to swap in a transmission from the same year GT.

[timmib]

Greetings all,

Thanks for the info. I kinda expected there weren't too many options. My thought was to simply reduce engine wear and tear. 131,000 on the odometer. Mpg improvement would be a bonus; got 25 mpg consistantly on the last trip (3 people, etc) and brand new Michelin's.

Thanks again,

Be well

[porcupine73]

Eh, the extra wear of running at a slightly higher RPM is completely negated by the wear of dry startups, that's where the bad stuff happens.

[1 Lucky Texan]

Eh, the extra wear of running at a slightly higher RPM is completely negated by the wear of dry startups, that's where the bad stuff happens.

plus, running at too low rpm leads to 'lugging' - increased pressure on bearings and increased cylinder heat.

[nipper]

plus, running at too low rpm leads to 'lugging' - increased pressure on bearings and increased cylinder heat.

Gearing, especially on small engines, is not as simple as adding taller gears. There is limited power, and ideally you want to be right on the edge of the performance curves, if not actually into them a bit. If you wander much from this, you can actually ruin highway performance by makingg the need to downshift more.

You are not hurting the engine, especially if you reduce your oil change intervals from 7500 miles to 5000 miles on a trip like this.

[Stelcom66]

My former '02 Outback automatic would run around 2600 rpm at 65mph. Prefering a manual transmission, I traded it in for an '02 Forester. That 5 speed runs around 2750 rpm at 65mph. I was glad to see that - a '98 Outback I had turned around 3200. My significant other just got an '02 Outback manual, like my '98 hers is around 3200-3300 rpm at 65. I wonder why - the engine seems to have plently of torque to run lower. I would think 500 rpm or so higher would mean less fuel economy on the highway - or maybe that's not enough to make a significant difference.