I'm totally stumped!

[EMIEVEL]

Hahaha...amputee humor.

Anyway, I have a 1993 with an auto and the thing is getting horrible mileage, like 10mpg towing my trailer. With my 1992 and a manual trans, I get about 14.5mpg towing the same trailer! Both trucks are supposedly stock, but the 1993 has had the injection pump rebuilt.

Could someone have messed up when they rebuilt the injection pump? It doesn't feel any faster or slower than the other truck.

What other things should I look for that will cause bad mileage? The transmission seems to be working properly. This truck seems to run hotter than the other truck and the fan is on more, but not enough to cause 4.5mpg in fuel loss.

Thanks!

Chris

[2muchtq]

I could see 4-5 mpg loss manual vs. auto. Our auto's do not have lock-up torque converters... and their efficiency is about 60-70%

[EMIEVEL]

So, is there a lock up converter available at a reasonable price?

One thing I noticed was climbing hills; in overdrive, even at 48mph, if I hit the button to turn off the OD, the RPMs would go higher. To me, it should have already been out of OD at that speed. Is my transmission not downshifting properly?

I know I'm not supposed to climb hills in OD but I forgot a couple times.

[cummins king]

you ever check the level of tranny fluid

[EMIEVEL]

you ever check the level of tranny fluid

I check it about every other fill up, along with the oil!

It has been a little foamy since I bought the truck on Christmas day. It also appears to be slightly over-filled.

Whatcha thinkin? Tranny slipping too much?

[cummins king]

it would explain the mpgs and not kicking out of od, but im no tranny expert, just from what ive heard

[CumminsPride]

Converter loss is my guess. Also, back the starwheel out a little. The truck may be fueling a little harder on the highway due to the load.

[Philip]

Lets get a little more info.

Where are you located?

How big is the trailer??

How much is your normal load in the trailer.

The PCM will normaly not shift out of OD till around 45 MPH or less. That is to low of speed for OD.

[EMIEVEL]

Lets get a little more info.

Where are you located?

How big is the trailer??

How much is your normal load in the trailer.

The PCM will normaly not shift out of OD till around 45 MPH or less. That is to low of speed for OD.

I'm in Apple Valley, CA.

The trailer is a 34' enclosed triple axle.

Trailer plus load is less than 10K.

OK, so most autos don't shift out of OD until 45. Mine seems to be shifting out of OD at that point.

The reason my mileage is higher than most towing is because I don't go over 55mph. There is a big fuel savings between 55 and 65.

The truck has 360K miles on it but that shouldn't be hurting my mileage. I've had 2 other trucks with that many miles or more and still had great mileage. It has 3:73 gears in it (2wd). When I'm not on cruise control, it seems my foot is almost always near the floor or on it.

I bought the truck on Christmas day from the original owner, who is an older guy. He said it was all stock except for a large auxilary tranny cooler and the rebuilt injection pump. I believe him. He had never even towed a heavy trailer because it didn't have a trailer plug and the only hitch was the bumper plate mount, it didn't even have a class 3! He showed me his records of oil changes and what not at 3000 mile intervals. He only drove it about 23K miles per year.

[dpuckett]

Check your valves, change the filters (fuel and air), and get some gauges on there, a pyro and tach being most important. The tach will tell you how much your tranny is slipping. While you're at it, change the tranny fluid and filter.

How'd you get 3.73 gears in there? Factory options were 3.54 or 4.10.

FWIW- I had a 92 dually with an auto that I towed about the same load in 2000. I averged 14mpg towing, and 19-21 empty.

Daniel

[SNOOT]

I have some pretty good numbers to back up a tranny as a cause of your problem.

3 years ago I had a complete transmision rebuild. Before my tranny rebuild I had been right at 12.5 mpg around town no load. After the tranny rebuild I got 16 mpg.
I think most of the increase came from the tourque converter the truck pulled real good.

After 3 years of drag racing and a couple sled pulls I am below what it started at around 11.5-12 mpg. My mpg has been getting worse every year since the rebuild.

I change the fluid every 25K and it helps but its short lived. The pan only shows clutch disc material and its very fine at that.

I am having a tranny built this time investing good money to see if I can get 6-7 years and a tranny that will cost less to freshen up each time.

I am told the converter is one of the best things a guy can do to improve your mpg followed by a good valve body.

Several on the forum from my reading will also tell you you can install a lock-up but you will have to find the engine adaptor and a doner transmision from a 94 or newer 46rh I think.

The T/Q will use up about 1" more space so you will need a new adaptor from engine to trans also.

All I really now is my mpg improved allot after my tranny rebuild.

JFYI That pump looks to be a rebuild also..

[Philip]

Those 3:73's aren't helping with milage towing. Your up in the RPM band pretty high. Staying around 55 MPH helps.

I bet that converter they put in was rebuilt to stock spec's. I wish you had a tach on it. Then you could see how loose it is.

[EMIEVEL]

Any idea why the ATF is foamy on the dipstick?

I'll check that rear diff ratio in the morning...I could be wrong and I think it is a 3:54.

[seeker1056]

plugged vent will cause foam
so will a near plugged filter

[cummins king]

doesnt a bad TPS also have somthing to do with the OD staying in gear