truck slows way down and I have to downshift back to third gear?

2002 DODGE RAM
130,000 MILES • 5.9L • V8 • 4WD • MANUAL
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RSCHULT189
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  • 2 POSTS
My truck has a recent rebuilt engine and transmission. It runs fine on low inclines and of course down hill. The problem is when we begin to ascend a 4 degree or greater incline I drop the transmission into third gear and increase my speed up to 45 - 50 mph, the rpm gauge is at 4 to 4.5 and I shift back into 4th gear (red line is 5), the truck slows way down and I have to down shift back to third gear.I can go 55mph max at redline. I live in Colorado and have to go over 12,000 ft mountain passes which have up to 7 percent grade for miles. I have to get out of the right lane and cruise behind the tractor trailers and maintain 45 mph if I am lucky. The kicker is if I have to carry or pull a load, the truck really slows down on the steep hills (25 - 35 mph). I did a test drive with the mechanic and he said it is ok to run just below red line for miles in third gear with a load on the truck. I am the original owner and when I purchased this truck in 2003 it traveled up steep hills with no problem with loads; I'm a retired construction worker. The whole reason I put in rebuilt engine a transmission was I figured it was more economic to put,$11,000 into it and avoid going back to monthly truck payments. I have been dealing with this nightmare for 3 years. Am I wrong and should just shut up? What would the problem be?
Oct 2, 2024 at 7:01 AM
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STRAILER
  • Experienced Mechanic
  • 55,233 POSTS
It sounds like the catalytic converters are getting clogged up, but I need to ask if you have gathered any codes from the computer?

This guide can help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Also, I have seen a weak MAP sensor cause low engine power as well, please go over this guide for more information,

https://www.2carpros.com/articles/engine-has-low-power-output

And this guide can help you test the catalytic converter if the truck still has one?

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

We need more information to help you. Please go over these guides and let me know what you find.


Oct 2, 2024 at 9:14 AM
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RSCHULT189
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Thank you. I will look at these guides. We just drove up 7 percent grade and topped out at 50 MPH empty load.
Thank you for helping me.

Bob
Oct 9, 2024 at 2:12 AM
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STRAILER
  • Experienced Mechanic
  • 55,233 POSTS
No problem Bob.
Oct 9, 2024 at 3:18 AM
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