I have a 1990 Ranger with the 2.9l V6 and what I am almost certain is the M5R1 Manual Transmission - 7.5 Rear Diff

One issue I haven't been able to fix is a rough take off

Only when taking off from a complete stop the entire truck seems to vibrate, to the point where my shifter shakes from side to side

Once I shift into 2nd gear and continue on there is no issues, smooth as can be

It feels like its coming from the back end and almost as if my tires are hopping

I tried doing a simple tune up (plugs and wires) with no luck, I am looking for ideas on where to start diagnosing this issue

I am not sure if this would be more of an engine, transmission, rear diff issue

It has not gotten worse, very consistent unless I don't try to speed up quickly in 1st gear - Then the vibration is less

Any insight is appreciated!

 

one idea, if you have jack stands. jack up the rear end just a few inches and get the stands under the axels. start it up and put it in first gear, look for bent driveshaft or warn U joints. I would think if it was a motor issue you would feel it in all gears?

 

I would think the same thing with the transmission as well, the truck does have a 4in lift installed b4 purchase, maybe the u-joints weren't installed correctly? Don't you think if the driveshaft was bent the vibration would continue?

 

to start with, crawl under the truck and try and move the driveshaft back and forth. look at the U joints. then check the trans output shaft, try and move the driveshaft up and down and sideways look for movement in the shaft. I dont know why this would only happen in first gear?