camaroeater

When im going 55mph it starts to vibrate near the dash area and around 70mph it gets worse. Once I let off the gas, the vibration is gone. If i slowy give it gas and stay under 40mph, I don't notice it.

Ive checked the U joints, replaced spark plugs, fuel filter and checked the cap/rotor & wires. It also idles perfect and doesn't miss, studder or anything. Also, fuel pressure is at 43.

Any ideas, this is really getting annoying? It started doing this 4 days before I got new/wheels tires.

conejo172

Check your alignment and tires/wheel balance! Those are the most common causes for vibration when reachim certain speeds.

camaroeater

I'm sure its not a wheel imbalance or alignment, due to the fact that once I let off the gas, the vibration is gone. Thanks for the input though.

Js88lx

pilot bearing???? Does the shifter vibrate allot..?

camaroeater

No, i doen't vibrate around the shifter. The vibration is coming from around the dash. I thinking it may be the balacer, but I replace that a couple of years ago and it made the shifter vibrate alot. Im gonna take another look at the balancer.

Dj_Seph

My car does the same. I've done the pilot bearing and u-joint.

It's like a very fast knocking in the dash, right?

AdderMk2

check your engine and trans mounts. however, if its speed related, it could be internal (transmission) or in your driveline. check rear diff fluid, and see if your pinion has any play in it.

.boB

This pretty much eliminates the suspension: tire balance, ball joints, etc.

Vibration under a load could a lot of things. Start by checking the simple stuff: timing, fuel pressure, clutch adjustment. Put a thermometer on each header tube and make sure they're all about equal.

You said you changed the balance a couple years ago; what did you use as a replacement? You might want to check that again.

Have you made any motor changes lately?

camaroeater

I replaced the balancer with a ford repalcement about 20k ago. It has no cracks in the rubber and doesn't budge when trying to twist it. I replaced the tranny mount with a urethane and stock ford motor mounts around the same time. I checked to make sure they're not cracked and the nuts are tight.

I ran KOEO/KOER again yesterday and came up with nothing. I did notice that if I rev it to around 4K, I doesn't shake at all and doesn't cut out or anything. Even when i go WOT, I notice NO power loss.

Adder mentioned the differential fluid, I should probably check/replace that. Bob., I did check the fuel pressure. Its at 43, vac line off and 32 with vac line on. Im staring to think i has to be the U joints, but i didn't feel any play in them.

I did have a Code 31 a couple weeks ago for low voltage at EGR. Could a bad egr cause these symptoms?

Thanks guys, I appreciate it!

Dj_Seph

Check the diff. That was my problem. Definitely need a trac-LOK rebuild...