Is my RPM to high? 2K @ 70 MPH

[KeckWerkes]

I just recently purchased a Yukon XL for my wife and noticed the RPM was higher at 70 mph than the RPM in my Tahoe. The Yukon, an 04 with the 5.3 engine, runs at 2K rpm at 70 mph while the Tahoe, an 02 with the 4.8 engine, runs at 1800 rpm at 70 mph. Does this sound right? Both SUVs are 2WD and have the 3.73 rear gear. The Tahoe gets around 20 mpg highway and the Yukon gets around 16 mpg highway. Is there anything I can do to get the RPM down in the Yukon and maybe improve on the MPG?

Forgive me I'm new at forum posting and not sure if I'm giving enough info.

 

[JKmotorsports]

What size tires are you running? Tire diameter will affect rpms at x speed.

 

[Tonygxp]

bet you the yukon has 4.10's

second thought does your converter lock?

 

[Nickleahy23]

I run at about 2k at 70 with my tahoe, 3.73s, and 32.5" tires

 

[Eagle]

yep. I bet the 4.8 has an optimistic speedo.

 

[KeckWerkes]

I don't know really how tall the tires are but the Yukon has 265/70/17 and the Tahoe has 265/70/16 tires. With the cruise control set on both trucks running side by side on the highway they will run side by side for miles at the same speed.

 

[Nickleahy23]

it basically comes down to the size of the XL...its bigger and takes more power to move and keep moving..

your tires on the tahoe are 30.6 and the xl are 31.6...so if they have the same gears, the tahoe should really be turning higher rpms then the XL..might wanna recheck that

just because they run next to each other on cruise means nothing...i can run next to someone doing 6k in the tahoe while they are doing 2k...

---------- Post added at 12:43 AM ---------- Previous post was at 12:41 AM ----------

bet you the yukon has 4.10's

second thought does your converter lock?

also a good point..from a stop you should feel it shift to 2nd, 3rd, 4th, and then lock up, depending on what the speed is set to for lockup stock..

if you give it some gas while you are cruising, but not enough to make it kick down..the rpms should slowly climb..if the jump up at all, the converter isnt locked

 

[m332is]

I don't know really how tall the tires are but the Yukon has 265/70/17 and the Tahoe has 265/70/16 tires. With the cruise control set on both trucks running side by side on the highway they will run side by side for miles at the same speed.

You have a big diff in tire diameter which will give two you distinct grearings. Were these factory size tires or aftermarket?

http://www.miata.net/garage/tirecalc.html

According to this calculator you have a 6.3% diff in your speedo reading.

Also keep in mind, that two of the same size tires from two diff companies (Goodyear vs Toyo) may have a slight diff in diameter as well for the same size listed tire.

Vince

 

[demonal]

Odd, I'm doing about 2k rpm @ 80mph and I'm on 26's

 

[thehoe92]

I run at 2k RPM and I'm on 295/35/24's
just checked today on the freeway after I read this thread

so it seems normal to me