I have been wrestling with a used F-150 that I bought recently. It has an automatic tranny, 302 V-8, two piece driveline. Also has electrically engaged overdrive.
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When I first bought the truck there was significant driveline vibration. This occured mostly from 25-40 mph. I had the U-joints replaced and the driveshaft (both of em) balanced. This did not work. So I had the truck looked at by two transmission shops to see if the tranny was causing the problem. They said no way, it was driveline.
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So I had a different shop check the driveline balance, and they said it was not balanced properly. They tried to balance the front driveline, but decided it was bent and replaced the tube. They then balanced it and put
it back on the truck. There was still significant vibration.
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So I had the same shop check their driveline balancing job and they decided that their machine was broken previously and that the driveline was still out of balance. So they re-balanced at no charge and reinstalled the driveline. Now there was still vibration, but significantly less. But it is still there and still annoying!!
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I also have replaced all the shocks and had the wheels dynamically
balanced twice. There is still vibration, mostly in the 25-40 mph range. There is no relationship to engine speed, only road speed, therefore I must assume it is still the driveline----but.
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Tonight it rained like crazy and weirdly enough the vibration, in the same speed range, got much worse. Only thing I could think of was brakes. Is this possible?
Your experience would be greatly appreciated.

 

These are the problems that make you want to pull your hair out. If driveshaft repair at one point really lessened the problem, then you are probably on the right track. Rotating assemblies that are damaged then repaired are almost never perfect again even if they balance to "0". You may have to replace the driveshaft completely. If it is not a driveshaft problem here are several other suggestions. Check verticle and horizontal run-out(out of roundness) of the tires, wheels, front discs, rear axle hubs, and driveshaft; all on the vehicle. If the ride height of the vehicle has been altered check rear end pinion angle. You might even try simply exchanging the front and rear tires and seeing if that moves the problem; indicating a wheel or tire problem. This problem could be a little complex to trace down, so be patient, and try the simplest cheapest things first. I hope this helps, good luck.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
4-wheel disc/ABS,Chestnut/Parchment,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification,Superchip,
Dynomax ultra-flow welded 3" cat-back.

 

Take the frame extensions (lift kit) out and put your truck back to normal driveline angles.


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Y2K™

XLT SC SB 5.4L E4x4 AW-Disc, 3.73LS, Skid, 7700# HD Towing, Chrome LT-245, Steps, Captain's, 6CD, Tonneau, keyless, Toreador Red, called "Nick"

 

Thanks for the input. Truck has not been lifted--so factory driveline angle still intact.

I think the damaged driveline is the issue, and retubing the front driveline has minimized but not cured the problem. Problem focuses on front driveline, not on rear. Balancing also syncs with "0" comment---as there is apparently some flex and/or heavy spot on the tube which only shows up at certain RPM, not at other RPMs. On the new driveline topic----unfortunately, the dealer says a new drive line is $800+. May be time to visit my local junk yard in search of a rebuildable driveline or two. Anybody know where to buy a new one cheaper for a 94 F-150 Xtracab?

 

At long last the driveline vibration has been resolved. Took the dealer 2 weeks of mucking around. Finally tested the 2 piece driveline in a unique way---they got the driveline repair mechanic to somehow run a balance on both shafts coupled together. Apparently it showed up some weird combo of slop in a new u-joint which was replaced. On top of this, the dealer came to the conclusion that the rear transmission housing and bearing were damaged, so replaced both. I had the bearing replaced before and it didn't do anything.

Anyway, net result was the thing runs very smooth now from 15-35, which is where it was shaking the worst.

 

Congratulations, all of your patience finally paid off. I had a trans tailpiece/bearing worn out on a Ford van and it definitely had some wobble. Also, if your not careful when you install U-joints, you can damage the driveshaft or yolk; pressing or beating on them. Have fun driving your smooth vehicle.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
4-wheel disc/ABS,Chestnut/Parchment,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification,Superchip,
Dynomax ultra-flow welded 3" cat-back.

 

Solved this problem. The folks that pointed toward driveline setup problems were correct! How this truck came from the factory with incorrect driveline angles is beyond me!!!

Anyway--out of frustration last week, unable to get anybody to solve the weird vibration problem occuring from 20-35 mph, I bought one of those SmartTool electronic levels. I proceeded to start measuring the driveline angles. The pinion working angle was 0.0 degrees. Not healthy. Supposed to be at least 0.5 degrees to keep the u-joint grease moving around. AND, the long shaft to short shaft working angle was 3.0 degrees---fine for the u-joint, but very bad news for cancellation/vibration effects. The shaft u-joints are supposed to be within 1 degree of each and in opposite directions, to get a quiet running driveshaft. After mucking around for a week with axle shims, and other garbage, the angles are pretty much textbook perfect. And behold, the vibration is gone!!!

Amazing---wish I had purchased some sort of accurate inclinometer months ago. The SmartTool is accurate to 0.1 degree, so you can get much greater precision that the $15 magnetic inclinometer that Home Depot sells.

The SmartTool costs $89 (Amazon) without the level frame, or as I bought it locally in Denver for $105 at a hardware store---which incluced the aluminum level frame. It is very consistent and makes the measurement of driveline angles truly simple. I also think that Spicer makes a much fancier version for around $300 retail----haven't seen one except for a picture at the Las Vegas Drivetrain web site.

My kudos for those that originally suggested a driveline angle problem!!! I wish I had the SmartTool then and had gone out and measured them immediately. It would have saved a great deal of frustration.

Mark

 

Need to explain the May posting---it only solved the vibration issue temporarily which is part of what made this a crazy issue to resolve. The installation of a new u-joint on the pinion end would take care of part of the problem---but the u-joint was slowly being destroyed over time---but until the last week I wasn't replacing the u-joints myself--I was having a shop do it. Big mistake! Once the joint was damaged, it didn't matter if driveline angle was perfect, if balance was perfect, nothing. Only is the balance and angles were perfect first did the u-joint survive. I actually witnessed this by setting the angles improperly with a new joint----within 5 miles it went from quiet operation to vibration. Changing the angles back to the proper level did not help----as the joint was now damaged. New joint with proper angles---everything is smooth and no failures so far.

 

Happy to see that science paid off. Nice investigating work, Mr. Starke.

I just posted a first-hand experience at: https://www.f150online.com/f150board...ML/000650.html


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Y2K™ Jim

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"