Hi i have a 91 300-6 with an e40d transmission..... i have noticed a shaking in overdrive that seems to be possibly tranny related or TQ converter? it does it with mostly anything below 1400 rpms anything over that it seems fine and when i turn off OD it stops the shaking

any ideas? thanks

 

Don't go guessing at the problem, pull the codes and know if there are any problems related to powertrain control, if there isn't then your problem is vacuum, fuel, or spark related.

BTW.. what gearing does you truck have? If it's typical for an I6 truck you shouldn't be using OD at anything less than 60mph anyway.

 

yes i def should pull the codes never thought of that!..... and its 3.55 but i also have 33" tires on..... at 60 mph with overdrive off i would be turning about 2200-2300 rpms if not more and if your familiar with the I6 that is screaming

 

That's far from screaming in an I6, if it was a cummins 5.9 then yes, but not for a gasser. My I6 with the M5OD runs ~1450rpms at 60mph, and I use OD at 35mpg as itkeeps my RPMS under 1k in town, saves a LOT of fuel as I idle around town. I also have the 2.73 rear gears.

How long ago did you do a good tune up? It could be almost anything, but I'd start at the ignition system and work my way around to the transmission.

 

yeah when i said screaming i was somewhat exaggerating but my point being there would be no reason to turn od off when crusing at 60 mph unless your aiming to suck down a lot of fuel... when i cruise at 55 (majority of my driving) i turn 1400-1500 rpm which is about the best gas mileage i can prob get........

i was also leaning to tranny because (sometimes) the shaking will stop when letting off the gas

and what do you mean by ignition system?

 

It could be almost anything, but I'd start at the ignition system and work my way around to the transmission.

 

My truck does this I had m5od swaped to zf still does it I did a tune up but im lost its a low rpm bucking feels like idk im with ya man

 

No I wasn't suggesting you turn off OD when cruising I meant just getting up to speed. My thought on the shaking is that it could be a lean stumble caused by a leaking thermactor(air injection) system or crossfiring plug wires, this will be most obvious when the engine is under maximum load which is lugging in overdrive.

 

thanks conaski! how would i figure out if i have one of these issues?

 

lock up convertor is slipping(at that slow of rpm). Try some additive to fix it. If not, do a full fluid/filter change and put some Mercon 5 in it. Should clear it up with some driving. What happens is the fluid breaks down, the clutches won't release smoothly, thus "chattering". Once you get some new fluid in it and drive it, it will start to smooth out.

My '95/302 truck did it when I bought it. Fluid fixed it. My '89 just started to act strange when I bought it. Did a service on it and has been fine. Both trucks were at the 90K mile mark.

Check fluid and see if it is getting old(turning dark red).

 

Pull the codes, torque converter slip and/or a lean mixture can get flagged by the computer even if the cause isn't directly related to the control system.

 

thanks guys will be pulling the codes as soon as i can....i wouldnt doubt that a need a good fluid change on the tranny also

 

One way to check for converter slippage is to apply just enough brake pedal to light up the brake lights, of course in overdrive at speed, this will cut the converter lock up, if it's converter slippage it "should" smooth out..

 

thanks white i will give that a shot as well

 

**Update* i finally got the chance to run my codes and got 334 which is EGR valve....could this cause a shaking which can now happen in any gear but sometimes does not

thanks!!