engine shakes 38-45mph

[cajundave]

hey guys i have a 2000 f 250 7.3 with 236,000 miles. i have noticed in the last 15,000 miles the engine tends to shake a good bit (shakes the whole truck) when i am at 38-45mph. it shakes both accelerating and when braking. i have noticed that it shakes more when braking; especially when i have to hit the brakes for a quick stop. it does not shake at any other speeds, it only happens when switching into the last gear or when leaving the last gear.
def. not a transmission problem.

anyone know why this might be?

[dieselEX]

At that speed it's probably drive shaft related, u-joints, balance issues, pinion angle. Check the u joints first. Higher speed stuff is usually tire related.
Good luck.

[Hank]

Crew cab? Long bed? Check your center support bearing on the driveshaft. Will do that when it wears. You didn't have it mudding right before the problem started did you? Keep us posted on what you find.

[6liter_BigSkyStroker]

Check your Motor mounts and trans mounts. I had the same problem on a 99 f superduty and the right motor mount was torn in two.

[C.Gift]

Originally Posted by Hank

Crew cab? Long bed? Check your center support bearing on the driveshaft. Will do that when it wears. You didn't have it mudding right before the problem started did you? Keep us posted on what you find.

Originally Posted by 6liter_BigSkyStroker

Check your Motor mounts and trans mounts. I had the same problem on a 99 f superduty and the right motor mount was torn in two.

I'd be more inclined to say the bearing, unless you've been noticing a little more vibration than unsual on startup. But honestly, anything is possible. Check both, you can never be too careful. Let us know what you find, good luck!

[ToMang07]

Originally Posted by dieselEX

At that speed it's probably drive shaft related, u-joints, balance issues, pinion angle. Check the u joints first. Higher speed stuff is usually tire related.
Good luck.

[cajundave]

thanks a bunch guys!! i will get into it tomorrow and let you all know what i find

[cajundave]

ok guys. i did not lift the truck to perform this task. so if i need to then i will have to back and do it again.

-the u joints along the the drive shaft to the rear axle all seem very good with no play.

-the transmission mounts look good.

-the drive shaft going to the front axle has a good bit of play. the u joints on the shaft did not have any play. when i say play; i can turn the shaft around 1" of play. i have manual locking hubs and they are set in free.

-not able to check the engine mounts, because i am not sure where they are exactly. does anyone have a pic they can post?

thanks a bunch!

[cajundave]

Originally Posted by Hank

Crew cab? Long bed? Check your center support bearing on the driveshaft. Will do that when it wears. You didn't have it mudding right before the problem started did you? Keep us posted on what you find.

Hank, the truck is a crew cab, regular bed. How do I check the center support bearing. I do not take my truck mudding, but if you have ever driven on Louisiana roads you would know that things wear out pretty quick on vehicles. If I had to guess, we probaly have some of the worst roads in the nation due to our sediments.

[cajundave]

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