Truck will not accelerate

Do you have any grinding or hard to engage gears? The most likely thing on a manual transmission that has a lack of acceleration is a slipping clutch.

https://www.2carpros.com/articles/clutch-doesnt-work-sometimes-or-not-at-all

The fact that this happens in overdrive is another indicator that the clutch is not transferring the power from the engine.

Do you have acceleration issues in any other gear or just 5th?

https://www.2carpros.com/articles/clutch-symptoms

Let's start with this info and go from there. Thanks

Hi,

Have you scanned to computer for diagnostic trouble codes? Does it accelerate normally in other gears? Is there anything you can do to force it to run normally in 5th gear?

If you haven't had the computer scanned, start there. Here is a video showing how it's done:

https://youtu.be/b2IJGfImVvw

If you don't own a scanner, most parts stores will do it free of charge.

Let me know what you find. Also, let me know the engine size so I know what we are dealing with.

Take care,

Joe

Hi,

Have you checked the transmission fluid to make sure it is clean and full? The fifth gear and reverse work off the same hub assembly. Does it always grind going into reverse? Even if a synchronizer was bad, you shouldn't experience power loss.

If you look at the pic below, I highlighted the gear assembly #33, the retainer #34, and the synchronizer for reverse/fifth.

If you haven't already, inspect the fluid and make sure it's clean and full.

Let me know what you find.

Joe

PS: It doesn't seem like the clutch is slipping, correct? For example, do the RPM's increase but the vehicle doesn't accelerate?

Hi,

Okay, that is the 305ci. Basically the same as the 350 (5.7L) with a different bore and stroke. Still a very good engine.

As far as the issue, there really isn't anything in the transmission that would cause a power loss in 5th gear only. What I suspect is happening is this. I have a feeling the clutch plate is worn and you only are noticing it in 5th gear simply because that is the gear that places the most load on it. Also, it could be the cause of the on and off grinding you get into reverse. IF you double-clutch it before shifting to reverse, see if it still grinds.

Can you tell me if it is 4wd? Also, I need you to pay attention when in 5th gear to the engine RPMs. See if there is any variation between the RPMs and the vehicle's ability to accelerate

Let me know if it is 4wd. I can get you the directions for repairs.

Take care,

Joe

Okay. Do me a favor. When climbing a hill in 5th, let off and then hit the throttle hard to see if there is any indication of the clutch slipping. Let off and on the throttle quickly and do it a few times if needed.

Joe

Okay, that doesn't sound like the clutch. If it was slipping, you would have noticed it. Have you had the computer scanned at this point? The interesting thing is this. Placing a manual transmission in 5th gear doesn't affect anything that would cause a power loss other than the idea that the gear ratio itself is designed for higher speeds, which by nature causes lower power.

Let me know if you've scanned it at this point.

Take care,

Joe