I have a 78 f100 with a 300 I6 and a 3spd with an overdrive. when I shift into overdrive it makes a sound almost like a grinding noise. The truck still pulls fine and there is no noise in any of the other gears. could it be that the linkage just needs to be adjusted? Any thoughts gratefully accepted.

 

OK, you have a 4 speed trans, with 4th over?

Or do you have a 3 speed with a separate OD?

I think you have a 4 speed. Anyway, does it grind like you've botched the shift, or does it grind all the time in 4th?

 

asumming its a manual tranny (you did not sate) and its has to be a 4 speed the syncros are bad.


I just noticed you have a 78. In that case i have no clue because ford never offered an OD transmisson

 

Sorry, I didn't word that very well. It is a 4 spd standard. It shifts fine but, once you shift into OD the noise from the tranny is somewhere between a grinding noise and a howl. Could it be a bearing?

 

If the noise is constant in 4th, it must be a bearing and/or shaft. See here for pics. The OD gear is pretty small.

Mine makes funny squealing in 1st and 2nd....

http://www.davidkeetoploaders.com/imposters.htm

 

Thanks for the info 85e

 

Drive someplace quiet with smooth pavement and see if the noise is there in 2nd gear, and in neutral with clutch engaged.

I once helped a friend with similar noise in a late 70's F150. His turned out to be the bearing on front input shaft, the one that carries the clutch. His transmission was a 4 spd, 4th was overdrive. The noise was there in all gears except third, but you didn't notice it in 1 & 2 because it was so faint. In 3rd gear (straight through) there's no load on that bearing because the cluster gear is just idling, not transmitting load, so it's pretty quiet.

When the bearing finally failed 1st and 2nd became noisy, and we got crunching noise as pieces of ball retainer made their way through the gears. You could even hear the bearing noise in neutral with clutch engaged, which isolated it to either that shaft or needles in cluster gear. We figured they're in bottom and always have good lube, so it had to be that input shaft bearing.


Fortunately it's pretty easy to change that bearing, unfortunately it's the very last part to come out when taking tranny apart. Hardest part of reassembly was those needle bearings between input and output shafts - a bit of vaseline or light bearing grease holds them while you sneak the back shaft in. We stood the transmission upright on a coffee can for that assembly.

Good luck!

Great Photos, 85E!!

 

Thanks for the tip I will have to check that out.