My brother-in-law just took his '96 to a shop because it was running rough and shaking a lot and apparently there is excessive crankshaft end play. He's bringing it by tonight so that we can take a look at it. Any suggestions on what we should be looking for? If there is too much end play, does that mean he needs a new thrust bearing or that the harmonic balancer needs to be tightened? I have a dial indicator and can get an accurate reading of the end play, but I'm pretty sure it will require pulling the radiator. Thoughts?

Thanks!

 

Crank or cam? I thought some trucks had issues with the cam gear walking a little that caused rough running. The fix for that was to shim the CPS.

Is the play up and down or in and out? Did they say how much play?

 

The mechanic said crankshaft, but didn't say how much. Anyhow, we took a look at it tonight and didn't see any noticeable end play. But it definitely runs a little rough at idle and peaks about 1400 rpm. From 1500 all the way to 3500 it runs real smooth.

We unplugged the MAP sensor but there was no change. Then we swapped IDMs with my truck, but again there was no change. After swapping the IDMs back, we took it for a drive and it seemed to run fine, but after a quick ramp up to ~3200 rpms and letting off the throttle I think one of the injectors misfired. It felt like a gas engine backfiring. It didn't happen again the rest of the way home. So it seems to be random.

Here's some more specs on the truck: '96 F250, 5 spd, down pipe and exhaust (no cat or muffler), and a TS chip (canned tunes I think, I put it in stock mode before the test drive).

Any suggestions/thoughts on the shaking? Motor mounts possibly? (wouldn't account for the misfire though)?

 

Oh, he's had it to 2 different mechanics in the past few months and both replaced a couple injectors; so it has 4 brand new injectors. And the last mechanic aparently checked the UVCHs and said they are good.

 

Manual or Auto tranny? If its a manual, it could possibly be the DMF on the way out causing the shaking...just a possibility, although it wouldnt account for the rough idle. Could be seperate issues however.

 

sounds like the rough running at low RPM could be from having a mix of injectors in there. I've always heard that you should replace them all at once (assuming they're all reasonably old). if the brand new ones are injecting better atomized fuel than the old ones, it would obviously run rough. then, at higher RPMs there is a faster rate of compression and more residual heat from the last compression stroke which will be better at burning less-well atomized fuel. ...but then of course, it could be many other things.

about the crankshaft endplay. if I stare at my crank from over the driver's fender with the engine idling, I see my crank pulley bob up and down ever-so-slightly. when I first noticed this, I was afraid I had main bearing problems, but I then climbed under the truck, grabbed the crank pulley with both hands and bench pressed it as hard as I could, then, hung on it with as much body weight as I could put on it. there was no movement of that sucker whatsoever, so in the end I just chalked it up to a bad harmonic balancer - which I've yet to replace.

again, not to say that this is the case with your brother's truck, but diagnosis of excessive crankshaft end play seems like a very severe diagnosis to make without any supporting details. i'd ask them to define 'excessive' and explain their measurements...

 

I thought about the DMF, but that should be a constant shaking and not smooth out over 1500 rpms. I took a look at it, but there's not much you can see with out pulling the tranny. And he doesn't have an inspection cover; so if any parts have come loose, they would have fallen out by now.

On the crank end play, the mechanic is suppose to be researching it and will get back to him soon. I've already told my brother not to let him do anything to 'fix' it until he actually shows him the 'excessive' play because we couldn't get the harmonic balancer to move at all last night.

 

I would explore the possibility of the DMF going bad, it is unfortunate you don't have the inspection cover I'm almost sure you would find parts in the bottom of the cover pan. There is a way to check the DMF using a large screw driver or small pry bar to put pressure on the flywheel or clutch part and check for any play or movement. I didn't need to do that test when mine went bad because I found ball bearings and other stuff in the pan. The vibration and shaking that you describe sounds very similar to what I was experiencing. I also had diesel mechanics that misdiagnosed the problem, which didn't help matters. I wound up replacing injectors too before I realized it was the DMF. The good part for me was now I have stage one Injectors and replaced the clutch with a valair.

 

So it would smooth out at the higher rpms? I will look into the DMF some more. Any suggestions on what to look for and how?

 

Yes, mine would smooth out at higher rpm but still there and I still had pretty good power, I was very lucky that mine didn't explode on me. After I did injectors I thought it would just take a little time to get the oil system cleared of air, some had said it would sometimes take some hard driving and miles to clear it up and get it running right, I brought it up to 70 and 80 a few times (dumb luck)
In other previous posts some other members had mentioned to take the cover off, but being a stubborn old fart I just couldn't believe a clutch would cause my problem (little did I know)

Here are a couple of links with pics that should keep you amused for a while, good luck solving you problem.


https://www.ford-trucks.com/forums/9...hlight=DMF+bad

https://www.ford-trucks.com/forums/1...came-from.html

 

I'll look into it tonight. I'll put a tire iron on the ring gear and see how much differential rotation I get between the 2 pieces.

 

Well, it's not the DMF, it has already been conerted to a SMF. Any other suggestions?

 

I checked the fuel pressure and it was really low so I pulled the reulator plug and found that the spring was broken. I replaced it with an extra one I had and a BB to get the fuel pressure back to about 55 psi. Unfortunately, it still shakes around 1100 rpms. It's not a rattle you teeth out shake, but it's certainly worse than my truck. I could really use some more suggestions.

 

Have you checked the uvch yourself?

 

My truck does the same thing. Sitting still in neutral, I can bring the RPMs up to 1100 and it shakes the whole truck. Like you said, not a rattle your teeth shake, but it shakes the whole truck. I just did Stage 2s, T500 and a chip. Had this problem before all that. Did those mods, it ran good for two days, then right back to the same crap.