95 Ram 1500 360/5.9 Gas, Automatic transmission, Reg Cab, 8 ft. bed, 2WD:

About 3 months ago, this started happening.

When the fuel tank is full, my truck shudders - no codes. Between 3/4 and 1/2 tank, usually smooths out, runs/purrs like it should. 1/2 and under...back to shuddering.

Took it to my usual shop - they found some fouled plugs and cap/rotor and coil needing replacement. All done, still shuddering. OK, so thinking transmission now.

Took it to the shop that rebuilt it last 2 times, good reputation in community, great guy. He checked it, said transmission was fine but saw a code 27 which was cleared after replacing the coil. Still does its weird thing.

SO - thoughts? Things to check? Anyone with similar experience? Please let me know. Looking forward to hearing from y'all. THANKS !

 

Need more details. What other conditions does it shudder? Full throttle?

 

I imagine they were done, but i didn't see specific mention of plug WIRES?

 

are you getting any Evap DTCs or any DTCs at all?

 

You aren't driving past a bunch of ugly people are you? Your truck might just be sensitive. Seriously, have you checked your universal joints on the driveshaft? I had one shudder are certain speeds but not others. My current truck has a vibration over 75 mph but I normally don't drive that fast. I get poor fuel mileage normally and high speed drops it even more.

 

kevinb70 - no codes other than that 27, new coil made that go away

Keith_L - wires are good

ol' grouch - I thought about u joints too, but it shudders with trans in PARK sometimes, so driveshaft not moving

MoparFanatic21 - No specific conditions seem to stand out - I usually start it and let it sit for about a minute to wake all the fluids up and get them to circulating (336K miles - compression checked about 1 yr ago, still tight, fuel pressure measured at rail was right in middle of acceptable range)

Thanks for all the replies so far ! I am still looking and checking stuff, so please keep any suggestions and advice coming. For sure, I will say what it was when I find it !

 

A couple of hyears ago, I did a major tune up on my '96. When I got into it, I found a lot of little things and some not so little. One thing I didn't expect was the harmonic balancer was coming apart on my engine. Take a look at yours and see if the rubber inside between the metal pieces is straight or coming out.

 

You all know that before you put the transmission in gear, you need to put it neutral for 30 seconds to a minute, right? It will make your transmission last much longer, in park, the transmission front pump is NOT circulating fluid, hence "check idling hot in neutral" on your dipstick. Just my two cents worth

 

Well, not really. However, if you have a lot of miles on the transmission, slipping it into neutral for a few moments will make it go right into gear. On older high mile units, the front pump seal can be worn and if it is, the fluid in the torque converter will seep down into the pan if it sits for a while. Sometimes overnight. Slapping it into gear it will take a bit to pump the fluid up and you sit until pressure engages the clutches inside. By going into neutral, the front pump will fill it immediately.

 

The pump is pumping in park, but, it isn't charging the torque converter, which can hold a LOT of fluid.