I have a 2001 f150 2wd 4.6 with 169,000 miles on it with a 2'' lift. I have new shocks on front and rear. new front end parts. When I have my cruise control set on 50mph my truck will start shaking and I had my tires balanced yesterday and it is still shaking pretty good but not to bad and my pinon angles on the drive shaft looks good. what should I check or do?

 

It is a shake or a low grade engine miss??

where do you feel this shake....In the seat?? from the steering wheel?

considering that you just had the wheels/tires checked...that can/should rule out snow or ice build up on the inside of the rims.

have you checked the tranny fluid to see if it low?

 

my trans was low

 

my truck is still shaking at 50 after I added trans fluid

 

It's your rear gear oil. The fluid begins to break down @ about 100,000 miles.

It'll tear the tuck apart if you don't take of that. - Shake the truck right off the road as well lol.

 

Does it shake at a certain speed or does it shake all the time above 50mph, or does it shake at 60mph, 70mph? where do you feel it, in the steering wheel or the body of the truck?

 

Yea, that shake can feel like it's coming from the trans... Nope, - from the way you worded it, - I bet it's the rear end, - almost sure of it.

 

Roadie (Does it shake at a certain speed or does it shake all the time above 50mph, or does it shake at 60mph, 70mph? where do you feel it, in the steering wheel or the body of the truck?)

it shakes at one speed then it goes away around 55mph. I feel it like it is underneath the body of the truck

 

Check your u-joints.

 

I had this happened to my truck, my truck would shake and felt like it was having trouble getting into another speed also at 50 mph range, thought i had a transmission problem but turned out i had a misfire, turned out it was the spark plug, i changed it an since then no more problems

 

I recommend you get it checked at a local auto parts store to see if it throws any codes even if it doesn't have a check engine light. Good luck, hope everything turns out well.

 

I checked my truck for no codes found. I checked my ujoints last night one of the looked rusted in the rear. I didn't get the rear fluid change at 100,000 miles but I will look into that tomorrow. and today I notice my truck has a little shake after 45 the shake is worse at 50 then near 55 it still noticeable. and I will have them to check the roundness of the tires

 

My 2cents (that's all I can bet, house limit) is also on the U-joints....might not be loose, but rather dry and is binding just at that spot.

BUT as others mentioned...changing out the gear oil in the differential certainly could not hurt and is due just on a maintenance level.

also might not hurt to re-grease the slip yoke also just on a maintenance level.

Still wouldn't rule out low grade miss fire just yet either

 

You must use 75w140 synthetic gear lube, and if it has a limited slip you need to add a bottle of Ford friction modifier.

If you have over 100k and have never changed the spark plugs, they are overdue!

 

Make sure you post up after you figure it out. Just so I can , - told you so lol.