From a chart I got that the GU4 has a ratio of 3.08. A person responded to another post of mine and stated that GU4 has a ratio of 3.73. I plug both of them into the calculator and this is the one for the 3.08. Believe me I'm not going 99 mph. So what do you have for correct GU4 ratio.

 

It's possible that someone changed out the factory GT4 3.73 gears for 4.10 gears, but unlikely.

Another consideration... When the torque converter locks up, the RPMs will drop by ~250RPM. The TC won't lockup until the engine has reached a certain temperature so if you made your observation on a cold engine... And will unlock if the brakes are activated or if accelerating.

When it comes this calculator, the loaded tire radius is the dimension from the center of the axle to the ground under load. The numbers you posted were using a loaded tire radius of 15". If you have a 30" tall tire, that dimension will be less than 15" due to tire deflection where it meets the ground. A 235/75R15 tire is ~28.9" tall and would likely have a loaded tire radius of ~14.1". You should confirm your loaded tire diameter for better numbers as this has a pretty large influence on the calculation.

I find it much more likely that something was wrong with your transmission when you were making your observations or you weren't in 4th gear with the torque converter locked in.

 

So this might help out, our tranny is basically a 700r4. the new version is a E which is an electric unit. the years you stated will have overdrive as stated by Swartlkk. Unless you had a problem all along with the tranny. As for gas mileage I have a 1998 4x4 with a 4 door 4.3 and get 14.7 (just filled up) if you are not 2 things to look at, a tune up or your heavy foot.

 

BTW: here's the result of the calculator with 4.10 gears and an effective radius of 14.1" tire diameter:



Scott, assuming the tachometer and speedometer are correct, having had the gears in the front and rear axles swapped to 4.10:1 would explain the high engine speed at 70 mph. (Both sets of gears should have been replaced for the 4wd to work properly.) This would make your Blazer have a more aggressive gearing, just not in the transmission.

BTW, for the above calculations assume the speedometer reading is your actual speed. This is why I asked if you had checked your speedometer against the speed reported by a GPS.

But as swartlkk pointed out, it would be important to check that the torque converter is locking up properly. If it is not locked up, it will be slipping and the engine will have to run faster for the same ultimate speed.

 

The observation of RPMs was made over years of owning a car. If I'm driving 70 miles per hour for 3 hours I would assume it is warmed up. (A heavy foot has nothing to do with it since it is on cruise control.)
I bought it as a fleet vehicle so no changes were made to the differential.
The one thing that puzzles me is a comparison when driving other S10s. When they go into 4th
(Overdrive) there is a substantial and noticeable drop in RPMs. That can only be in the transmission not the differential. Regarding the mileage please see picture. It is the specs of a 2001 four-door two wheel drive.

 

I would agree with your observation.

 

Scott,

My understanding is that the 2wd Blazers tended to have lower rear-end ratios and along with less mass to move and less friction in the drive train would be expected to get much better mileage than a 4wd version which more than likely had higher ratio gears in the axles.

As for your anomalous high engine speeds at 70 mph, can you confirm that your speedometer is accurate? Does it agree with what a GPS reports? Is the tachometer accurate? What size tires are you running?

 

Scott, no point in disagreeing with swartlkk about ANYTHING regarding these vehicles.

He knows EVERYTHING!

Not.

No one person on this planet does.

Just saying.

The only thing that can be agreed on about these vehicles is that they are GM junk.

At best, when they work as intended they are mediocre vehicles.

However, usually, they have FAR more problems than most equivalent vehicles from that era.

Truth hurts.

 

Wovon man nicht sprechen kann, darüber muß man schweigen.
we weren't arguing just trying to keep him honest. I would much rather have an intelligent discourse on molecular biology, biochemistry, organic chemistry or quantum mechanics then to try to figure out GM mentality. But I digress.

 

It's interesting that you chose that moniker yet you despise GM vehicles