My truck gets a bad vibration between 35 and 45 mph until I stomp on the accelerator and get it to kick down in gear. Any ideas on what it could be and how to fix it? I've been told it's a misfire, but wouldn't I notice it at idle too?

 

A guess would be a bad TC clutch but no you may not notice a misfire at idle.
My 460 had a plug wire off an it idled smooth but shook under load on my last trip.
Put a KV probe on each plug wire at the rocker cover and I seen that #6 wire was off the its plug.

 

I'd also check the U-joints. My truck did the same thing but through the 45-55 mph range.

 

There are plenty of causes for vibration. If your truck has an E4OD transmission it is well known to exhibit torque converter shudder at low speeds. A good test is to use light throttle to get the transmission into 3rd or 4th gear, just as you feel the vibration lightly tap the brake pedal. This will force the torque converter to unlock, if the vibration disappears...congratulations you have torque converter shudder.

My last '93 Lightning had it really bad when I purchased it. Once I determined it was indeed this dreaded phenomenon I could make it come and go at will with a light tap of the brake ( Or as we found out the Lightnings also release the torque converter clutch with the Hazard blinkers on).

I did a complete transmission flush and fill using a procedure I found on this site. After replacing about 18+ quarts of fluid the problem was gone. Others have used Lucas or other products, but I shy away from those if at all possible.

 

U joints are all new. I've checked and rechecked my pug wires and the tranny guy said it wasn't TC shudder. I have an aod trans if this helps. Thanks for the replys guys. I'm still open to more ideas.

 

i think i may possibly have the same thing... although mine only does it around 1000 rpm.... not sure if its the shudder or not but i do have the e4od... so thanks rla... i will try that and see if it helps

 

Have you checked/adjusted the TV cable? That adjustment is critical on these AOD transmissions.

 

most deffinately...Mine quit after i did doughnuts in a parking lot xD

 

most deffinately...Mine quit after i did doughnuts in a parking lot xD u joints that is

 

My truck did the same thing at 35-45 mph. So I put on a new stabilizer on it and that fixed it. I don't know if this will help or not, because as rla said it can be a number of things.

 

not to hijack the thread or anything but i tapped the brakes when mine started the shudder today as Rla said to do and ill be darned..it went away!

 

Good news/bad news, eh?

 

I tried the tap the breaks trick but it came right back 3 seconds after. It shakes from 35-about 50. Its been happening for About 3 months. I also notice a loss of power. I had all plugs changed and a new distributor cap. What now?

 

I assume we're dealing with a 4R70W or E4OD here? The "tap the brakes" trick will only unlock the TC for a few seconds, after which it will go back into lockup. If you manually shift from OD into third gear, but maintain the same speed/TP, does the shudder go away? What transmission fluid are you running, and what condition is the fluid in?

 

The torque converter unlocks when you apply the brakes.

Your results lead me to believe that you do have the very common E4OD torque converter shudder problem. I assume you have an E4OD transmission? I highly recommend a complete transmission fluid and filter change: Changing ATF Fluid in a E4OD and 4R100 transmission .: Articles

If the problem persists you have bigger issues.