swapping 1998 V8/4R70W/4406 into 1999 SOHC 2wd

[ahuggins6]

I've quite a few miles on it over the past couple days. The same EGR code keeps coming up. New DPFE will be here today. For $20 I'm not even gonna take the time to test the old one. The hoses are good. It's gonna be a pain to swap because the Trans dipstick is right up in the way of getting a socket/ratchet on it even with extensions.

It's got a pretty loud roar starting around 68mph and getting worse the faster you go. Feels/sounds like a driveshaft out of balance. So I just now backed it up in the shop and got under it to find the yoke has lots of play in the tail housing. Looks like I need to replace the bushing and probably order a new yoke to get that tightened up?? I bought new U joints early this morning, but that's not the problem. There's no noise when going from forward to reverse. Just a high frequency vibration with the roar.

 

[410Fortune]

The slip yoke has a bunch of play? That is odd? How much plunge do you have? At ride height about 2” or less of shaft should be visible behind the seal

Vibration at 65 is why I move the t case to passenger side 1/4”

 

[ahuggins6]

I tried to get a good clip of the play. There’s more than this clip shows but…



And here’s a shot of the plunge. I’ve got the cheap caliper set at 2”. I’m gonna change the u joints while I’ve got it out and I’ll look at moving the rear over that little bit. I thought from what I’d read on other threads that mine WAS moved over. I did put some pull on the rear to get it over before I tightened the motor mounts.

 

[ahuggins6]

And then I find this, so I Know the u joint wasn’t put in correctly, and is probably out of balance.

 

[410Fortune]

That is not a lot of play from the slip yoke side to side seems about normal?

If you unbolt the shaft from the rear axle will it push into the t case more or is it bottomed out? From your pic it looks to be near bottomed out. You need about 1.5” of plunge to be available at ride height

Hmm driveshaft looks a bit tight, there should be some of the smooth shiney surface showing behind the seal that d shaft I bet is 1.5-2” too long

That I joint is installed and the snap rings in place, I mean I have seen worse! It’s not perfect but I doubt that is the issue

 

[ahuggins6]

It's got about an inch and a half to slide in. Definitely not bottomed out. I've already ordered the bushing and seal, so I'll replace those and see if it changes. I'll probably work on moving the case over like you said, but honestly, I need an explanation of how it makes vibration go away.

This morning I drove it about 60 miles. It doesn't really vibrate anymore. But above 72mph, the roar starts. I'm wondering if that's a bad bearing in the T case. AND. There is more movement in the slip yoke that that video shows. I don't have an idicator or I'd measure it.

 

[410Fortune]

Okay well after doing 5.0
Conversions into these trucks for the last 18 years we noticed once in a while, mostly with 4 door explorers… that we would get a vibe at 60-65. This is with the 4406 t case 4r70w trans
My friend Brett went through heck trying to solve it on his personal truck
He replaced the 3rd shock
He balanced rear shaft
Upgraded mount
Still vibe

Over the course of two years I researched the issue. It was determined by people way smarter than me that our setup has the rear driveshaft angles basically too perfect. Not enough deflection in the u joints. I know when I set these up I end up with a 7 degree pinion angle and pretty much exactly 7 degrees at the tailhousing. By moving the t case to the pass side 1/4” or so we introduce some side deflection and hopefully solve the vibe. That’s when I started making my custom crossmember and utilized the urethane f150
Mount
Huge improvement over stock
Unfortunately none of my personal trucks or trucks i have had the vibe, I mostly do rangers and I always upgrade the trans mount and force the t case over a bit
Also my rigs are usually lifted.
I’m not saying that’s what it happening on your build, I’m just explaining where this advice comes from
I have seen the vibration in about 5-7 explorers over the years

 

[ahuggins6]

OK, so there's no vibration to speak of. Just a roar. And it occurs to me that I've heard of people changing to a different gear oil in the rear end to fix a squal or something. maybe that's what I'm hearing? I DID top off the rear end with some gear oil I had and maybe it's a different weight than I need?

 

[Josh P]

I tried looking back several posts in this thread, maybe my reading skills suck and I missed it but could you describe the roar sound? Does it sound like it is coming from the rear of the vehicle? Does it sound like a jet engine spinning up? My van had a jet turbine sound that ended up being the fan clutch not free spinning.

 

[ahuggins6]

I tried looking back several posts in this thread, maybe my reading skills suck and I missed it but could you describe the roar sound? Does it sound like it is coming from the rear of the vehicle? Does it sound like a jet engine spinning up? My van had a jet turbine sound that ended up being the fan clutch not free spinning.

I can't tell where the noise is coming from but it's not the fan clutch. I'm familiar with that on this vehicle and my super duty also. this sounds like it's probably VERY high frequency vibration that I can't feel thru the road noise. And I can't imagine the driveshaft spinning fast enough to make that kind of vibration. So I'm thinking its oil in a bearing somewhere, maybe even in the transmission?? I have all the stuff to build another rear end and swap them out, but I'd rather find it before I get around to building another rear end.

 

[410Fortune]

Put her on jack stands and run it in gear, find the noise? Carefully of course

The 8.8 rear axle can take 80W-90 or 75W-140 the same axle was spec'd with both lubes from the factory over the years. must add friction modifier if you are limited slip.

 

[ahuggins6]

Put her on jack stands and run it in gear, find the noise? Carefully of course

Thought about it... Honestly it sounds like a bad wheel bearing. But a bad bearing makes noise at all speeds, right? All the ones I've experienced did. Or they were an obvious intermittent noise. Like hitting a bump will cause it to start or stop. But this roar is silent until about 72 and then it fades in to a strong, loud roar at 75.

 

[410Fortune]

wheel bearing will usually make noise under a side load, so good way to narrow it down to wheel bearing is a little side to side action while driving, when heading straight less noise, when leaning side to side should be louder. That is tell tale sign of wheel bearing
Do not take it up to 78 mph on jack stands! hahahahaha also don't point truck towards the house

My stepson worked at a tire/alignment shop for 3 years, he taught me how they do front end shake down test and help spot a bad wheel bearing. With wheel in the air grab the spring or shock, and spin the tire, if you feel vibrations or roughness in the shock with the tire spinning, usually a bad bearing.

 

[ahuggins6]

Yeah, the vehicle needs to be pointed out the door AND on jackstands. AND chocked. AND maybe tied to the floor?? Like a dyno!

I've ID'd plenty bad bearings that way also. I just don't get to leave home enough these days. Working from home SUCKS. Not really, but.. there are down sides. I think it might also be tire going bad, or getting bald. I've got plenty tread, but three of the tires were put on new in about 2018... With this 4wd swap, I intend to put something bigger on it, but I was hoping to work all issues out before sinking tire money into it.

 

[410Fortune]

Rotate them see if noise
Moves

 

[ahuggins6]

Have you ever had an exhaust drone noise. My dad's 79 F350 had glass packs and when we'd stop in traffic it would pick up a drone and rattle my ears. This roar is like that in the way you can't identify the direction, but it's not a vibration. It's all around. IDK. i really need to go drive it some more. I intended to do the side to side weave yesterday to see if it changed, but I didn't get on the interstate to get to 70.

 

[ahuggins6]

OK I’m driving the explorer right now. It’s got to be a vibration in the drive shift. I feel it in my feet. I feel it in the steering wheel. I feel it in my seat. It goes away when I let off the gas. it gets worse when I gas on it. All I can imagine is that little bit of play in the slip yoke is keeping that front you joint from center and up on the output shaft.

 

[410Fortune]

It sure could be! Very odd to have looseness there at the slip
Yoke unless something is just plain worn out

 

[ahuggins6]

Is there a difference between the plastic DPFE on the SOHC and the metal one on the V8? With the EGR flow code, one of the suggested fixes was replaceing the DPFE sensor. So I put the plastic on it. Now the code for DPFE sensor voltage comes up after several miles of driving.

This morning I swaping the explorer knuckles over to the ranger knuckles because my front brake pads were NEARLY gone. I've never driven a vehicle with this little pad! Maybe I'll get around to working on the T case output bushing and seal. And MAYBE I'll spend some time moving all that over a touch. Also, I noticed puddle of trans fluid under the transmission about 2" diameter, and the vehicle has only sat there an hour.... yay.

 

[C420sailor]

According to Rockauto, it’s the same Motorcraft sensor. So unless the MC part is more universal than the ones that came from the factory, you should be able to swap them between SOHC/5.0