Hello,

Here is my issue, a bit of a long story so bear with me.

Late last year I bypassed the radiator. No issue prior to that, I did it once I found this forum for another issue which was the the driveshaft u joint bearings. However, since i found out about the bypass I did it.

About a month after that I went on a 350mi road trip non-stop. Towards the end of the roadtrip the car started shuddering, I felt it under my seat, a deep rumble. Since the car never lost power and I was close to my destination (about 10mi), I completed the trip. Through the week during my stay, the were no issues to report. Upon the return trip the same thing happened. The rest of the time since, the issue never repeated (about 10mos). I kept on searcing the inet, and I've read most of the stuff under the sun, but could not find a similar problem.

Last month i went ahead and installed a second external xmission oil cooler, and changed did a drain and fill, using Valvoline Max LIfe, like the year before. I went on a 350 mi road trip. On the way down, I made one 20 min stop. No issues to this point. Toward the end of the trip and within 5mi of destination, I noticed a slight shudder.

The rest of the week, everything went fine. On the return trip home, I made the 350mi trek non-stop. Within 20mi of home the shuddering started. Never lost power, so continued home. Again, the issue never repeated while at home.

Prior to a 850mi roadtrip this weekend, fearing heat, I reconnected the bypass to original, and left the secondary cooler installed. During the first 3 hrs of the trip (240mi) no issues, made a 30 min stop. The next leg was 4hrs and (320mi), the shuddering starting. Initially, mildly while coasting, i.e. downhill or when letting off gass for other reason. A couple of times, I turned off overdrive to see if it had any effect, but it did not. Again, there was no loss of power. I made another 30 to 40 min stop, and proceeded through my last leg of the trip, us 77 through the apalachians. The truck accelarated through the mountains just fine, the last 20mi of 77 going through Charelston, I started to notice the shuddering again. As I got off the interstate to proceed through some back roads for the final leg of the trip, I noticed a little hesitation when accelerating initially from a stop. However, the transition through the gears was smooth, and the rest of the trip was at speeds of less than 70mph. That was the last 100 miles.

Once in town, I notice a bit more power required to get out of the hole and first gear, but no hesitation in shifting. I arrived at destination last night.

A couple of things I noticed that may be coincidental or have bearing on the issue, or may not but may be worth mentioning. If I tap the accelarator while the shuddering is active, I can make it go away about 90% of the time, while the rest 10% it continues. Some times while making high speed turns through the apalachians, i.e. above 60mph and coasting, it appeared to go away. Some times it appeared to go away if I passed over a rough spot on the road while shuddering. Other times it did not matter. Also above 75mph almost 80, there is vibration, almost like high frequency, which I think just my tires as they are a bit worn.

This morning the truck is fine like if nothing ever happened :/?/?/?/?????.

Something aint right, but cant figure it out.

Any suggestions? I am going to do a drain and fill again, before departing. However, I am a loss here. Unless the tranny is caputs, but you would think it would do it all the time.

I do have an SES light, but it is for the fuel qty sending unit and the vacum leak from the little valve on the canister back behind the left rear wheel.

Edit: 128k miles. Never towed while I've owned it from 47k.

I hope one of you have an idea.

Thank you for your time and interest and Merry Christmas.

Regards,

Hey there,

If you have any doubt that your transmission has been contaminated with coolant, I would suggest you send some of your trans fluid out for analysis to see if there is any glycol or H2O in it.

Best of luck.
t

I've got the same shudder still after doing cooler bypass and rebuilding the tranny. Thoughts?