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I have a 1994 bronco with 4wd auto. I love the truck but repairs are killing me. The current problem im having is around 40 mph when accelerating i feel a heavy vibration but i let off and it seems to stop. I have a new transmission, new driveshaft, and a rebuilt rear end. Now the diffrental shop says its the axle shafts, and the axle shaft shop says its the differental. Im hoping the wheels are out of balance. Please help.
 

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84 Bronco, 351w, c6, custom doubler, np208, 5.13’s, TTB44, 9”, locked f/r
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944 Posts
Is it lifted? Kinda sounds to me like the driveline angle is wrong, and gets even more wrong under acceleration when the rear end torques up under load
 

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Yo Grahamer,
Welcome!

"Vibration, technically, is a high-frequency trembling, shaking or grounding condition, felt or heard, that is constant or variable in level and occurs during a portion of the total operating speed range. The types of vibrations that can be felt in the vehicle can be divided into three groups:
  • vibrations of various unbalanced rotating parts of the vehicle
  • body and frame vibrations excited by powertrain, wind or road inputs
  • tip-in moans or resonance vibrations from stressed engine or exhaust system mounts or driveline flexing modes
For engine or accessory vibration, all speeds, refer to Pinpoint Test D in the Diagnosis and Testing portion of this section.

For high-speed shake/vibration, 80 km/h (50 mph) and up:

  • Refer to Pinpoint Test A in the Diagnosis and Testing portion of this section and to Section 04-04 for tire conditions contributing to shake/vibration.
  • Refer to hub and rotor runout checks in Section 06-00.
Vehicle vibrations can also be subdivided into those that occur at low speeds and those that are most noticeable at higher speeds. Since the dividing line between low and higher speed vibrations is not clear, there will be vibrations that overlap the two ranges.

Typical Low-Speed Vibrations (Less Than 72 km/h [45 mph])
  • exhaust vibration
  • engine harshness
  • driveline vibration due to improper driveline angles
  • power steering pump disturbances
  • air conditioner compressor or drive belt (8620) vibrations
  • take-off shudder (driveline problems)
  • brake roughness or harshness
  • driveline roughness
  • driveline slip-yoke or rear axle universal joint flange (4851), automatic or manual transmission clutch slippage
Typical High-Speed Vibrations (Above 72 km/h [45 mph])
  • rear axle universal joint flange runout or imbalance
  • driveshaft (4602) imbalance
  • excessive tire-wheel and drum assembly imbalance
  • tire roughness due to high non-uniformity (force variation) or out-of-balance condition
  • rear axle pinion gear pitch line runout
  • excessive tire and wheel runout
  • worn suspension components
  • front end accessory vibrations
  • exhaust vibration (greatly reduced in exhaust systems de-coupled by a flexible coupling and mounted with blade and block hangers)" by Ford for 96, but applicable to your 94.
●⊙●
ASAP, find out if speed control recall work, if equipped was completed @ Recalls Look-up by VIN (Vehicle Identification Number); or @ Welcome to Ford Owner | Official Ford Owner Site; or ... have VIN ready. While there, see most Ford dealer maintenance/repairs done @ any dealership nation-wide.
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."
See this guide by jowens1126 to confirm recall status @ 93 & 94-96 Cruise Control Recalls Repair
Note that the 93 recall is different than 94-96.

For any Bronco questions or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories (75 posts required to view due to scammers who preyed on our members.).

To save you time and for better responses, please fill out your Bronco info with location, year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. .
Bronco info is now able to be put under your user name.
Click your profile button in the top right and go to account settings.


On that first page, named Account Details, scroll down to "Vehicle Info" and type in up to 100 characters.

Now you can simply enter your information in the text editor and click save.

Our Forum FAQs includes for example, How To Upload Images To Posts, How to Use Search & more tips!

➡See BabaLooey's Favorite FSB Links (lots and lots of tech links) ... includes such as, "Tailgate Window repair & troublehooting.

1994 Bronco Brochure, Partial; Cover & Page 3; plus pics of EDDIE BAUER model accessories.
by BigRob at 1994 Ford Bronco Bronco Accessories pictures, videos, and sounds | SuperMotors.net

Try to find time to participate in our Full-Size of the Quarter & Full-Size of the Year Contests @ Voting
You will get ideas by those competing. Also see the prizes! They are awesome as compared to other sites' "contests"!
Al
 
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