Rear End

[JPUETZ]

I have a 1978 Bronco with stock 3.50, 9in rear end, the rear end totally stopped working. I was able to run in 4 wheel to get home. I pulled out the axels and rear end and found the pinion yoke spline was stripped. I assume something jammed up in the 3rd member causing this to happen, at this point 3rd member semes to be working properly spinning it by hand.
I will probably replace the 3rd member just wondering if this is common or anything else I should be looking at?

Thank You
Joe

 

[miesk5]

Yo Joe,

"Since it broke, the gears dropped out of location and are not riding on the side gears=will not transmit power. One of a couple things: Someone dumped the clutch and sheared the pin because all the power is transmitted through it. Or, someone was spinning one wheel real fast, then it caught and the reaction of the two small gears from instantaneous change in speed caused it to snap." By Freightrain

See 9" Rebuild & Gear Setup GREAT ARTICLE!
@ http://www.fnc.ch/index.php?page=279&printview=1
Excerpts:
9. INSTALL DIAL INDICATOR AS SHOWN. MAKE SURE DIAL INDICATOR IS EXTREMELY RIGID, OR RESULTS WILL BE SKEWED. ENSURE DIAL POINTER IS SET SO IT TOUCHES THE TOP OF ONE GEAR TOOTH AND IS TANGENT TO THE OUTER ARC OF RING GEAR TEETH. HOLD PINION ****** SOLID AND ROTATE RING GEAR BACK AND FORTH, ENSURING PINION/****** DOES NOT MOVE. PLAY SHOULD BE EVIDENT AND THE AMOUNT OF BACK AND FORTH PLAY IS CALLED BACKLASH. IT SHOULD BE AROUND .008 TO .012 INCHES.
10. PAINT ALL RING GEAR TEETH, BOTH SIDES, WITH GEAR MARKING COMPOUND (USUALLY A WHITE TYPE OF GREASE). PUT FORCE ON RING GEAR IN EITHER DIRECTION (SMALL RUBBER PAD PRESSED AGAINST RING GEAR TEETH WORKS WELL FOR THIS). SPIN PINION/****** BACK AND FORTH, 10 OR 20 TIMES, ENSURING 5 OR 6 RING GEAR TEETH MESH WITH PINION GEAR TEETH. RELEASE FORCE ON RING GEAR AND ROTATE IT TO A POINT WHERE PREVIOUSLY MESHED TEETH (PATTERN IN GREASE) CAN BE SEEN. PATTERN SHOULD LOOK LIKE CORRECT MESH PATTERN IN DIAGRAM BELOW.
13. USING LARGE ADJUSTABLE WRENCH, HOLD PINION ****** AND REMOVE PINION NUT. REMOVE 5 BOLTS HOLDING PINION, PINION BEARINGS AND RETAINER TO MAIN CASING.
●14. REMOVE PINION ASSEMBLY. CARE SHOULD BE EXERCISED TO PREVENT DAMAGE TO RUBBER O-RING ON PINION ASSEMBLY. ENSURE METAL SHIM(S) BETWEEN MAIN CASING AND PINION RETAINER ARE ACCOUNTED FOR AND NOT DAMAGED. SLIDE PINION OUT OF RETAINER (MAY NEED TO BE PRESSED OUT) AND PRY OFF PINION SEAL ON END OF RETAINER."

 

[chrlsful]

yeah, replace w/above BUT - U must Dx the initial cause or go thru this soon again. I suspect big tires, wrong pinion angle or some1 "got on it" like a drag from standing still...

 

[muddrivermike]

I suspect big tires, wrong pinion angle or some1 "got on it" like a drag from standing still...

You mean big tires like mine, or ME getting on it causing this?

 

[miesk5]

yeah, replace w/above BUT - U must Dx the initial cause or go thru this soon again. I suspect big tires, wrong pinion angle or some1 "got on it" like a drag from standing still...

Yo. I wrote "Since it broke, the gears dropped out of location and are not riding on the side gears=will not transmit power. One of a couple things: Someone dumped the clutch and sheared the pin because all the power is transmitted through it. Or, someone was spinning one wheel real fast, then it caught and the reaction of the two small gears from instantaneous change in speed caused it to snap." By Freightrain

 

[NotaVegetarian]

Have a Detroit locker in a 9” with 3:50 gears and 31 spline sitting on the shelf if your close enough will make you a deal on it. no axles or yoke

 

[NotaVegetarian]

Have a Detroit locker in a 9” with 3:50 gears and 31 spline sitting on the shelf if your close enough will make you a deal on it. no axles or yoke

Sold Sold Sold. Sorry no longer have the third member available, made a guy a deal $400.

 

[miesk5]

Yo Not,
Good for everyone!

 

[johnnyreb]

Yo Not,
Good for everyone!

I read where the only gear on the 78-79 Bronce ,s was only 2 gear ratios and they were low. I have been thinking about going to a higher gear to help the mileage I think one of the ratios was 4:10 and the other was geared lower.Thought it goes real good in 2 wheel drive. Very seldom do you have to go in 4 wheel. Thank for this information Mike. Hope your eyes are doing better.

 

[chrlsful]

look @ WHOLE drive line B4 a change (add in which motor 300, 302, 351, 400M).
(engine) Transmish, Transfer, Rear Gear, Tire Dia
Save some $'n use an on-line gear caculater to 'play' w/different options on each component. Last KNOW what U wanna achieve.
hi mileage, good mileage, average, lill help, moderate, monster off roader/strip mo`chene.
There may have been only 2 offered oem (355 & 410?) but after mrkt is extensive (see preceding 6)..