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Discussion Starter · #1 ·
I have read probably 20 suggestions for my rear end "CLUNK" upon accel. Can anyone tell me how to fix or narrow it down. I have heard slip yoke greased, u joints, gears in diff., axle rotating in u bolts lengthening shaft....
Can a Bronco enthusiast tell me what to try first? It has to be a common repair if it is so prevelent in Broncos. Thanks so much for you help. Maybe someone can help me narrow it down to 1-2 things as now I am totally confused as to what to try first. Maybe I have read too much????? Thanks for your suggestions.
 

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Put the back end up on jack stands, both sides, then
What Steve said,......
..and maybe,...Old pinion gears and pinion pilot bearing.
(need more information)
How many miles on the rear end that you know of ?
"Original axle and gears ?".
 

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Discussion Starter · #3 ·
Truck has 180,000 miles. If I do this and there is play??? No play??? Orig. rear end. Could this "clunk be from that many diff. things??? To Everyone who offers suggestions;THANK YOU VERY MUCH!!
 

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After you put it in neutral, wiggle the drive shaft , if it wiggles at the u joints you need new ones. U joints should be tight.
 

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Discussion Starter · #6 ·
Alright I did what was suggested. lifted rear end in N and wiggled shaft, No play in u joints. But then when I spun it by hand very sharply, it felt like there was some play in gears somewhere. It was like it traveled 1/8-1/4 inch before wheel engaged. any advice????
 

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Discussion Starter · #9 ·
Has anyone heard about these, could this really be my problem???


Traction Bar Basics:Traction Bars hold the axle in place during acceleration and stopping. This improves traction and directional stability on raised vehicles, especially. Overall,they help eliminate shackle and driveshaft problems during sudden stops, hill climbing and rough trails. They also reduce the chance of broken springs due to rough terrain with heavy loads. Excellent for Broncos used in the sand dunes or for heavy mud bogging. They help to control wheel hop and axle wrap (the Bronco “clunk ”). When used with our double shocks and high strength U-bolts they will reduce broken u-joints.

Axle Wrap: The rear axle rotating in the U-bolts. Repeated axle
rotation causes wear on the driveshaft, U-Bolts and axle housing.

Bronco “clunk ”: Caused by the driveshaft snapping from extended to shortened position on acceleration due to the axle’s rotation.




Classic Traction Bars
Simple in design and function,attach above the springs so they don 't catch on trail obstacles. Come black painted with blue polyurethane bushings.Will not fit with overloads.
#5300 66-77 Bronco, 78+up Big Bronco & F150, $89.00
 

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that wont help if its in the gears, that would keep an ungreased slip yoke from clucking and hiding a problem, just grease the slip yoke and keep it maintained like your supposed to
 

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I have bets on the slip yoke.
Me too. Grease it up and see if it takes care of the problem. Generally if you had a problem with the axle or gears it wouldn't clunk on accleration. It would probably completly break and you wouldn't be going anwehere. If it clunks once on accleration I bet its the slip joint. If it does it again and again its probably something else.
 

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Alright I did what was suggested. lifted rear end in N and wiggled shaft, No play in u joints. But then when I spun it by hand very sharply, it felt like there was some play in gears somewhere. It was like it traveled 1/8-1/4 inch before wheel engaged. any advice????
The 1/8" is normal play. Is it a limited slip or open diff? Could still be u-joints even though they don't show any play. My limited slip loads up sometimes and just clunks. Is the gear oil old and gummy? Could be gumming up the clutches if you have a limited slip.
 

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I used to have a clunk everytime I would put it in drive. I would have to gas it slowly or it would clunk. IIRC it went away when I put on my lift. Check check your u-bolts to make sure they're snug and make sure all your front bushings are in one piece.

FWIW the bronco did that for years and years before I owned, it always did that when my dad had it since day 1 and it didn't cause any problems.
 

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My 96 has that initial clunk as well. When I bought the guy let me know so I had him knock off some money and anticipated have to rebuild something in the driveline. That was almost 4 years ago and now the only time i notice it is when someone else with me says, "what was that". I usually just laugh.
 
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