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I have a 1977 f150 step side 4x4 with the 400ci engine.
In the last month I've busted through two perfectly good ujoints, one timeoff-roading and the break was somewhat expected, but the last one broke after all highway driving.
These are the symptoms I've been experiencing. Some are due to the broken ujoint, but some are due to what I believe is causing the extra stress to be put on the ujoints and causing them to break (I need help differentiating between the two)
1. There's a loud 'clunk' as soon as I let off the gas while driving. It's coming from somewhere on the drive shaft.
2. Truck vibrates at highway speeds (bad ujoint, didn't do this before it broke)
3. When easing off the clutch there's play where the rear driveline attaches to the yoke on the rear dif. I can feel it as I let out the clutch and if I have someone else do it while I watch I can see it bending up. (I'm curious if this is because of a yoke and pinion problem or because perhaps my leaf springs are shot? If I ever gas it hard from a stop the back end hops badly.
4. With the drive shaft off, I can twist the yoke back and forth before it engages the axles. About a 1/8th rotation worth of play in either direction. I don't know if this is normal or if I should be concerned about gear backlash. Yoke bearing and everything appears to be fine.
I'm planning on stiffening up my suspension and seeing where this gets me- will a leaf spring helper be good enough or should I install all new leaf springs?
Is your truck stock? I.E. lift/blocks engine/ trans swap...
The trucks have wheel hop, most of the time a helper spring will not work. The axle is wrapping/ winding around the spring, when the tire breaks traction it will snap to the orientation it should be.
Read 77&79's suspension upgrades, he swapped the springs for HD Chevy's I am unaware if that solved the problem. You will see people with ladder bars and that will help also.
As for the u-joints, if any of the geometry has changed due to swaps or lifts the needles may not be getting full range of motion and will wear flat causing slack in the driveline. Proper driveline angles and lubrication will stop this from happening/ wearing quickly. When installing the caps be sure that all needles are upright and none have fallen into the base of the cap or broken, it should slide through the yoke with pressure but that's it.
The ~1/8" play is normal at the transfer case and axle are normal.
The clunk may be from worn mounts at the transfercase also, you have one on a crossmember and one on the driverside frame rail.
Hope this helps.
replace the u-joints then drive it. go from there. For #4 I'm thinking you are talking about the pinion for the rear axle that may be the spider gears I have seen worse.
Truck is stock. I'll replace the ujoint again and diagnose from there. Thanks for the suggestions. It's a fun project but always needs something!
Originally Posted by jbehuniak
Is your truck stock? I.E. lift/blocks engine/ trans swap...
The trucks have wheel hop, most of the time a helper spring will not work. The axle is wrapping/ winding around the spring, when the tire breaks traction it will snap to the orientation it should be.
Read 77&79's suspension upgrades, he swapped the springs for HD Chevy's I am unaware if that solved the problem. You will see people with ladder bars and that will help also.
As for the u-joints, if any of the geometry has changed due to swaps or lifts the needles may not be getting full range of motion and will wear flat causing slack in the driveline. Proper driveline angles and lubrication will stop this from happening/ wearing quickly. When installing the caps be sure that all needles are upright and none have fallen into the base of the cap or broken, it should slide through the yoke with pressure but that's it.
The ~1/8" play is normal at the transfer case and axle are normal.
The clunk may be from worn mounts at the transfercase also, you have one on a crossmember and one on the driverside frame rail.
Hope this helps.
As far as the pinion yoke goes, I wouldn't worry about back lash so much unless it is real bad. It's in and out up and down movement. If there is any of that then it's time to dig into it.
If you have a locker in the rear axle, that would likely explain the free play and klunking in the rear end. By design they have to have a little free play unlike spider gear setups.
Just a thought, I was going through u-joints every very 100 miles in a Bronco. Finally after installing a new u-joint one time I noticed the one bearing cap slid into the opening that is a press fit very easy. I swapped to another driveshaft and never had a problem since.
Where exactly is the u-joint failing? Is it always in the driveshaft portion or on the axle yoke? I would mark that position and see if future ones fail in the exact same location. When you tear it apart on the side that fails are the needle bearings nothing but powder and tiny bits?
Is the driveshaft "in phase"?? Here is a link to a cool video. https://www.facebook.com/Trustmeiamamechanicalengineer/videos/652429238232016/?fref=nf Hope it works.........
