Engine/Transmission (1994 - 1998) is my converter bad?

[rattle trap]

my single largest complaint is less than par gas mileage. i dont expect 25mpg but better than current.



my truck is a '94 standard cab long bed 4x4 AT 354 gears and 305/70/16 mastercraps and 230,000miles. no lift, no real mods. i do have a straight pipe 3" exhaust and a "holy" air box. very very close to stock. i have a 3 gauge ultralite setup but currently only have my boost gauge installed since i havent got to a drill yet. i have seen boost as high as 28psi, which does not correspond with factory specs. boost at cruise speed of 55mph is ~5psi. i assumed it should be lower?



the speedo has been calibrated to the tires and verified against radar. at 55mph my factory (inaccurate) tach reads 1625. now i know it isnt that precise i just mean directly between 1500 and 1750.



with all of that said, i ve been getting approx 16mpg on the road @55mph hand calculated over a period of several months. always right about the same. this is unloaded flat ground in southern michigan.



a few days ago i packed up to move down here to houston. packing included about 1,000lbs in the bed and about 5,000 behind me. i have no idea of the trucks weight but that shouldnt matter.



i was dragging my mustang on my dovetail 18ft car hauler for the very first time (never pulled anything before)



i had read that the engine should turn atleast 1750 to keep the pump psi up but less than 2100 to keep mpg in check.



that left me somewhere between 60-65mph. i was able to use my cruise control throughout indiana illinois and missouri. heading into arkansas i started to notice the truck couldnt hang in OD. at any slight grade if i remained in cruise with OD on, rpms would jump to 2250 from the normal 1750. quite a jump. i also noticed with od off i was only running slightly more at 2500.



with all of this taken in account, i still got 15mpg even through the ozarks with the trailer. so 6000lbs extra weight, 5-10mph more, and grades and i only lose 1mpg



im thinking i may be blowing through the converter even on unloaded trips? does this sound right or sound like a whole other problem?

 

[Missouri Mule]

I don't think so, sounds like your Overdrive/PCM down shifted the trans to maintain speed.

 

[rattle trap]

nope. like i said when i manually downshifted i ran 2500rpms in 3rd. there was a definite difference in power, rpm, engine sound, and throttle position.



i know i shouldnt be using cruise but this was a test. in over drive it required almost full throttle to hold a hill. in 3rd you could feel the pedal lift.



this is what rpms looked like @60-62mph

1750 in overdrive, converter locked. flat ground (load or no load)

2250 in overdrive, converter doing whatever its doing loaded up hill

2500 in 3rd what ever terrain or load.



so with those various rpms you can tell when it down shifted or not. actually come think of it, i dont recall a single time where it automatically down shifted on a hill. if i didnt push the button, it stayed where it was.



trying to figure out if a 500rpm difference up hill vs flat is a bad thing?



i apologize since i am new at this game.



i may have various other issues im not seeing. also trying to figure out the mpg thing. my mileage should be better unloaded. thats just common sense.

 

[edgeman]

You say that your milage should be better unloaded... . Yes in a perfect world and a gasser that makes sence. But on a diesel... especially a cummins... they are noted for pulling at the same mpg than when unloaded... and if you do drop mpg when you are pulling that isn't a bad thing either. I have a 97 dually that gets 19 to 20 when pulling grain wagons that gross 50,000 lbs loaded and when I am running down I-75 unloaded I get about 23 to 25 it varies on how much I am into the throttle. I hope this helps. It doesn't sound like the transmission or the converter is going bad but you never know.