I've looked and looked and looked for this one...sorry for the long post.

It will feel like rumble strips around ten times worse when going 10 MPH to 40. When I say violent shaking...it literally feels likes the rear view mirror could fly off. I can't imagine this would be TC issues. Vehicle has 120K on it. I can mitigate it somewhat by feathering the throttle.

Transmission fluid was serviced a couple years ago. It is pink, nice and clean, at correct level. When driving down the road she shifts fine. Granted, since this problem just happened this morning I'm not really into doing a comprehensive road test for fear of it grenading.

Dropped down below to take a look. Yoke out of the transfer case (around 1" visible is quite clean). Think I've replaced MPLS a few years back.

At this point I'm somewhat at a loss given the speeds I've mentioned. I'm actually leaning toward differential/driveshaft problems. Could the clutch packs cause this and necessitate a rebuild? Hard to describe, but it feels like is it coming from behind.

Edit: Just to add...no MIL codes. I know the difference between a misfire and this after replacing a bunch of COP's and plugs.

 

Well found the problem, not sure why it would happen.

Took it out this morning for another test drive. Long story short the yoke on the differential broke. Ujoint was still intact.

There was definitely metal on metal contact.

 

Glad you figured out your problem. The next time, I am under my truck I will be sure to check my yokes for any play or anything. Any pointers you can give would be great. FYI haven't had to service my drive shafts or do any diff work yet on this truck. New area for me.

 

Yeah, I figured out the problem. But it left the driveshaft on the road and gave me a soil my pants moment.

Guess biggest advice (and I spotted this earlier yesterday) is the yoke from the transfer case was shiny. As in, it looked like it was pulling out the transfer case a tad.

I didn't get a chance to check for play. Definitely will next time.

Only concern is i hope this didn't screw up something else. The yoke appears to be around a $65 part from Ford. After it got up to speed it drove fine so hopefully ring gear and pinion are a ok.

 

Welp, after one month this was the resolution.

I could write 1,000 words about the backstory...but basically...

1) Bought an entire rear end out of salvage yard.
2) Bought a set of upper and lower control arms (found a set on amazon, they are tubular) for about $200. Will outlast the vehicle.
3) It's back on the road and never felt better.

Stupid on my part for letting it happen in the first place. Upper control arm let go (due to rust) and within a mile of two of driving played heck with the rear end. Given the backstory you'd understand why I was looking at the wrong things.

Anyways, it is my favorite vehicle and I'm glad it is back on the road serving our family needs once again. Better than being salvaged.

With that said, and I've searched and searched...and pretty much know the answer but want validation....I want to replace the transfer case oil. Is Mobile 1 ATF ok? Is Mercon V ok with it?

Thanks.

 

Mercon V...no substitutions.

 

Thanks.

Was planning to do it this past weekend but got hit with another issue. Truck started to misfire. I'm not new to that situation with coils and plugs. Wouldn't throw a continuous MIL. So picked up a rebadged Autel scanner from HF, it read cyl 6 as pending. Replaced plug with Motorcraft, new coil, misfire gone.

Total plug change probably 30k miles ago along with O2 sensors.

Anyways, here comes my next question and bear with me.

The truck is down on power. It's been that way before the major surgery. While on vacation last month it literally couldn't get out of its own way on 7% grades going through the mountains. Transmission always wanted to downshift if I had the cruise on and the truck held the lower gear much longer than expected to get over the hump.

If I was manually doing the throttle, I could pretty much keep it from downshifting just by "feeling" how it was doing. Hard to explain I guess.

Another data point, tip in on the pedal from coasting and it stumbles a tad. And I also replaced the TPS, cleaned MAF, TB...they really didn't need it. New air filter as well.

So next I'm going to attach fuel pressure gauge and hopefully am able to monitor pressure while driving.

Given the amount of misfires it has had in its life I'm actually leaning towards the cats or a weak fuel pump.

Sorry for the train of thoughts. One thing that is weird, the scanner is totally out of whack for tps position and engine load. That should raise a flag, but the new TPS vs old TPS is the same. Idles perfectly. Drives great.

 

I would lean towards the cats being clogged, for the misfire reason.

 

Yeah...not my primary vehicle, so hard to collect data given sometimes I have to work evenings and the daylight is getting shorter.

But I had about a half hour tonight to grab some live data. Both S1 O2 sensors are all over the place which is good. Both S2 O2 sensors hold quite steady, which I view as good. Main question I would have is if a bad cat would "light off" and operate correctly even if they are restrictive.

Recreating the stumble is quite easy. When driving at around 45, trans in OD, tip throttle a tad and it stumbles. I can hold it like that basically forever creating the issue but it doesn't throw codes. Feels like a misfire.

So with that said, thanks for the help. My next step is to attempt to monitor fuel pressure under load. Not sure my gauge can reach the windshield from the rail.

Will bang on the cats with a mallet to "hear" any broken crap.

Replace fuel filter.

 

The lack of power you're experiencing in 9 out of 10 cases is either clogged cats or low fuel pressure, so you're on the right track. Keep us updated. Another way to check the cats is to remove O2 sensor 1 from each bank to give any backpressure a place to escape and then go for a drive. If you experience a noticeable increase in power then the cats are clogged.

 

Will do.

Diagnosis is tough sometimes when you search, then realize you are reading about a 3V issue, etc.

As for the O2 sensor, I can do that drivers side...but if I remember correctly doing passenger side is basically dang near impossible without having the exhaust droop a bit.

Going to pick up an IR thermometer and attempt to get some temp readings off the cats as well. Not just for this, but a good tool to have in the arsenal.

Depending on fuel pressure will look into regulator failures/vacuum issues as well. To be honest I haven't researched vacuum tests much. Also, had the DPFE code a few years ago, and cleaned out the passages which cleared out the code.

I'm not one to throw money at a problem, and consider this somewhat of an interesting mental exercise of what-ifs as I try to methodically work through the issue.

 

Fan clutch. I had a similar issue and the good folks around here suggested that I should replace it. when the fan clutch goes bad it drains the power out of the engine. Replaced mine today and so far truck is running great.

Who knew.

 

Tried searching for this issue but it is quite hit and miss reading up on it. Thanks for the feedback.

I hope to check for fuel pressure soon, my fuel gauge doesn't have the adapter for the Ford style shraeder valve.

 

A quick and dirty method of checking if the fan clutch is the cause of lack of power is to simply remove the fan and go for a (short) ride and see how it performs. Just don't do it on a super hot day and don't go somewhere where you'll get stuck in traffic. As long as you're driving, the engine won't overheat without a radiator fan.

 

Ok, gave the fan blades a toss.

Hot or cold acts the same...moves about a 1/4 of a turn.