Expy/lightning drivetrain issues

[toms89]

I have been having issues that I thought I would go ahead and post here.

The biotch about it is I believe its related to my modifications or as a direct result of them.

1) I have had what I consider a resonance type vibration in the gas pedal that seems to emanate from the floor but not nearly as noticeable as it is insulated and carpeted. The intensity seems directly related to outside temps as strange as that sounds. The colder the worse it is.. Engine temps makes no difference.

2) I have had an imbalance in the drivetrain that is noticable at speeds above 75 ish.

3) Recently I have had a very low rumble sound that becomes noticable between 35 - 45 mph and again above 70 mph. This was first noticed after I had my extra cats installed into the exhaust. Possible due to it being quieter.

I will go into more detail and troubleshooting I have done in following post in this thread.

 

[toms89]

As far as number 1 on my list.

Not convinced its not motor related though I have difficulty understanding why outside temps would effect it.

If anyone has been to the track and had an open exhaust car drive by and it makes your car resonate, that's how I would describe it. But it cannot be heard, just felt. It does not appear rhythmic in nature but random resonance that does not change.

At the time I tried to locate the source I did note that it could easily be felt in the exhaust though nothing could be felt with my hand on the intake of the motor.

My original though was its related to my dual 3" exhaust.

More on this later....

 

[toms89]

For number 2 on my list.

I had my tires road force balanced. I have new U-joints, front and rear in the rear driveshaft. I had it re-balanced.

Re-balancing the driveshaft seemed to help somewhat but the high speed vibration still exist.

One thing worth noting is the rear tailshaft is leaking and there is some play in the tail shaft. This could be a clue... There is play when you attempt to move the driveshaft but the U-joints are solid. When the transmission was rebuilt I had the transfer case gone through and it was given a clean bill of health but it was mentioned that there was some play in the chain. It also had new tailshaft seal put in of course. The driveshaft yoke appears in fairly good condition with no noticeable grove in it so why it leaks is a bit suspect.

 

[toms89]

For number 3 on my list..

Before I took it to the track I took it to a local reputable shop.

Had the mechanic which I know personally take it for a test drive. Old mustang racing buddy. He though he heard something but it was not obvious to him. Its like one of those that's subtle enough things that only the driver is aware.

He puts it on the lift. We pull fuse 104 so 4wd will not engage. Has rear tires up in the air and runs it up to speed. Listened to the various bearings and did not note anything of significance. We did note some noise coming from the transfer (different noise) which we assume was slack in the chain and it slapping around a bit.

Decided its best to wait rather than replacing or servicing parts unnecessarily.

 

[toms89]

I take it to the track and the vibration becomes much more pronounced at the top end. Typically keep it well under 100 on the street.

I make several passes but it appears it may be getting worse so I decide to call it quits before something lets go at top end.

On the long drive home I notice the vibration is significantly worse at speeds I do typically drive. So the high speeds or stress of racing definitely had an effect and no I am not really that surprised!

Here's where it gets somewhat interesting.

The vibration, resonance and rumble all got worse and appear somewhat more closely related. Now at speeds right around 40mph where the rumble becomes apparent it begins to resonate fairly harshly (gas pedal). The more the throttle the worse it is. I would swear it is the engine due to it being related to the throttle pedal and position but it does it directly related to vehicle speed and not rpms? When I park it, put it in neutral and rev it... no resonance??

 

[FordandPolaris]

Could it be wheel hubs? I have had to change the wheel hubs in my truck twice in the last 3 years or so, and every time, it is a hum/resonance that signals their demise. Though it is usually rhythmic. Like it fades in and out, and it is only highway speeds that I can hear it.

 

[toms89]

I will put that on the top of my list of things to check.

Now that is is worse I can re-check everything hoping it may be more obvious now. I had checked the front components in the past but one thing I did not do is run it in 4wd with all wheels in the air. May have to try that with it locked in 4wd if I cannot locate it otherwise. I was certain it was coming from the rear but the sound / vibration can be deceiving.

 

[1997SCEBFEX]

Tom, I mentioned drive shaft balancing, however you already addressed that.

Sure you also checked your motor mounts/bolts etc.

You said you had your tires road orce balanced; is there any chance that something is not balanced correctly. Not sure what the weather has been like up there, but any chance there is frozen stuff in your wheels?

If the chain is loose, perhaps it is being exacerbated under load? Does is do the same thing going down a steep grade, i.e. drifting? What about that same hill in neutral? How does it react when when you apply brakes, if at all? Conversely, what about up-grades too?

My overall deduction would be drive-train/line related as you described. How about the torque converter &/or trans proper/trans filter. Hows the tranny fluid?

 

[toms89]

Tom, I mentioned drive shaft balancing, however you already addressed that.

Sure you also checked your motor mounts/bolts etc.

You said you had your tires road orce balanced; is there any chance that something is not balanced correctly. Not sure what the weather has been like up there, but any chance there is frozen stuff in your wheels?

If the chain is loose, perhaps it is being exacerbated under load? Does is do the same thing going down a steep grade, i.e. drifting? What about that same hill in neutral? How does it react when when you apply brakes, if at all? Conversely, what about up-grades too?

My overall deduction would be drive-train/line related as you described. How about the torque converter &/or trans proper/trans filter. Hows the tranny fluid?

The tires were balanced, re-balanced then road force balanced so fairly certain they are balanced. But if there was a defect in the tire it would be difficult to detect. Wish I had a spare set to try.

No ice in tires. Not below freezing when it has occurred.

Not sure on the transfer case. Its possible there are issues with it. It has held up to far more abuse than I though it ever would. It practically goes into 4wd on the street anytime I get on it.

The rumble is present around 35-45ish mph and above 70. Found it a bit odd it was roughly twice the original speed when it re-occurs and that it was quiet in between.

I hate to admit that it does need new motor mounts and that I have them but yet to install do to the difficulty achieving the clearance to do so. The drivers side has a fair amount of "play" (allows the motor to lift) but there is no metal to metal contact at any time so I had my doubts it may be the source. I suppose it could be throwing the driveline angle off enough to create issues elsewhere.

 

[FordandPolaris]

Does your GoPro capture the noise or is it all exhaust note?

 

[toms89]

Does your GoPro capture the noise or is it all exhaust note?

The go-pro has very poor audio. My cannon hd video camcorder has great audio but the rumble I hear is very low frequency that it would be unlikely to pick up.

The vibration is just felt and not heard.

 

[Stoned06]

It's not a coincidence that the vibration occurs at 35-40, then again at 70 as the imbalance in whatever is causing the vibration hits it's frequency to cause it. How are your u-joints? My guess is that it is a rotational force, but could be a heat shield or loose exhaust system component.
I don't want to reread everything you posted, but is it regardless of what RPM you are running, or just at the particular speed at any RPM? If it's regardless of RPMs, then I would say rotational force. If it's at certain rpms running at those speeds, then it could be resonance in the exhaust.

 

[mindgame]

rear pinion bearing loose or more play than normal?

 

[toms89]

rear pinion bearing loose or more play than normal?

No. Very tight with zero play.

 

[toms89]

Well the saga continues.

Time to pay for all the abuse I have been giving it...

 

[mindgame]

Steelman Wireless Chassis Ear JS97202 - Arctic Tools - Discount Auto Tools

time for this...

 

[toms89]

Steelman Wireless Chassis Ear JS97202 - Arctic Tools - Discount Auto Tools

time for this...

Thanks for the link...

Led me to think about getting this bit more affordable wired set up...

Chassis Ear - Amazon.com

 

[mindgame]

I got the wireless.. Transmitter 3 always static out.. I think the wired will be much more solid..

 

[toms89]

Got under the truck today and listened while I had it idle.

I have a lot of noise coming from the bellhousing area. It sounds like a pretty noisy diesel. It was difficult to tell exactly where it was coming from but when I cupped my hand and listened to the bellhousing it could be heard very well. Did the same at the trans and engine oil pan... nothing.

So possibly converter or flexplate issues.

Also noticed my fan clutch has been sticking on. She blows a hell of a lot of air.. I'm sure that can contribute to vibration issues.

 

[toms89]

I just received the "wired" chassis ear to hopefully help diagnose my issues. But have not had a chance to use it yet.

Friday I replaced my harmonic balancer to eliminate it from the equation. No change and the original really did not look bad but it was relatively cheap and easy to replace. At least I can mark it off my list. :/

Also replaced my fan clutch while I was there as my fan has been sticking on for a few minutes when I first leave in the morning. Well...... now my expy sounds like a 747 about to take off practically all the time. Going to switch back to my stock unit.