I'm still shaking the rig down after reassembly. One issue at a time, right? Even before the new motor and trans, I always felt like their was a distinct rearward shift and very subdued "thud" when accelerating from a stop. Same thing when hitting the brakes from a roll. Gordon fabbed a custom cross member for the D20, so I don't think it's there. It feels like motor/trans is rocking back and forth, but the mounts seem ok. Any insight/clever ways of checking to see if the mounts are going? Short of having someone drive it with the hood off while I walked next to it, (I can't seem to identify the movement. It's not body related (as far as I can tell), and it is definitely induced by power/braking. Maybe jack standing it and giving it a little power? I think it requires power under movement to duplicate. Thoughts from the gurus?
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Rocking feeling at takeoff/stop.
- Thread starter JK
- Start date
You could lock down the engine with a ratchet strap between the head and frame, that at least could allow you to rule that out as a potential culprit.
Have you checked your leaf spring u-bolts?
Have you checked your leaf spring u-bolts?
I looked everything over, but I haven't put a wrench to them. I can feel it in the floorboard at takeoff, which makes me think it's isolated to the front end, but that could just be resonance. I'll double check the U-bolts. As for cargo strapping, that could be an issue with this engine compartment. I've definitley got 10 lbs of sh*t in a 5 lb box.
dave67fd
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You mentioned reassemby? What did you reassemble? Sounds like axle wrap as metioned. Have someone watch your axle as you take off. Ditto on checking leaf sping hardware. Maybe as little as slip yoke needing grease.
Tell us a little more about your setup.
Tell us a little more about your setup.
Would axle wrap cause a noticeable shift at idle? I can literally let the brake out and feather the gas every so slightly and there is a distinct weight shift rearward happening somewhere.
dave67fd
Bronco Guru
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What leafs are they? Stock, w/blocks, add-a-leaf. etc..I would first check torque tighness at plates and shackles. Are the bushings new? Check tightness at driveshaft.
Still sounds like axle wrap. Many times with just shifting into gear (automatic I assume) with foot on brake will cause axle to shift. Hold the brake in gear and throttle it up and down and you will feel up and down torque motion. A little is ok but a lot not.
https://www.youtube.com/watch?v=Xot9ha7n2ac
Still sounds like axle wrap. Many times with just shifting into gear (automatic I assume) with foot on brake will cause axle to shift. Hold the brake in gear and throttle it up and down and you will feel up and down torque motion. A little is ok but a lot not.
https://www.youtube.com/watch?v=Xot9ha7n2ac
... Cheat & take it to a good Front end Alignment Shop & tell them you have something loose Might be in front end ... Your not sure But would like an estimate. Pay for their best Guess. & say I'll gather my money up.
... I'll also say lay down on the ground beside it & let someone drive off forward while you watch under it . Even loose rubbers on the shocks can let you axle clunk.
... I put a short piece of chain on my 300 CID 80 BRONCO holding the motor down . Seems like I kept twisting the chain & had a long stud with a nut & washer too make it tighten up...
... On a 74 chevy truck I found a broken frame at the power steering gear box.
... I'll also say lay down on the ground beside it & let someone drive off forward while you watch under it . Even loose rubbers on the shocks can let you axle clunk.
... I put a short piece of chain on my 300 CID 80 BRONCO holding the motor down . Seems like I kept twisting the chain & had a long stud with a nut & washer too make it tighten up...
... On a 74 chevy truck I found a broken frame at the power steering gear box.
I went out and laid beside it and had the wife take off/power brake, etc. I'm seeing very minimal wrap on takeoff, nothing like the video. And that was giving it hell. When accelerating normal, there was basically nothing as far as I could tell. It has a 3.5" lift with 11 pack leafs, no blocks or add a leafs. I also pulled the hood and watched the motor, laid low and watched the transfer case mounts. No movement at either that I can see. I did notice that when I accelerate, then brake, I feel it in kind of a back and forth motion as the rig settles. So accelerating, rock back. Braking rock forward. Complete stop, back and forth one or twice. Very subdued, but enough to irritate me and worry me that something is hanging on by a thread. Maybe the leaf and shackle bushings? I checked torque on the leafs and shackles, all good. No slop in the drive shaft. It is sounding more and more like axle wrap, but to my surprise I didn't see any significant roll to confirm.
I appreciate the input! I'm spending more time trying to isolate it. I've figured out it doesn't even require throttle, just letting on and off the brake causes the weight to shift somewhere. I'm gonna go through the suspension and hope I find the smoking gun somewhere.
Well I think I've got it fixed (for the most part). I just spent a day rolling around and checking torque/looking for anything out of place. The list-
I noticed the passenger side tie rod end (1ton TRO with GM ends) was about misaligned from the drivers by 10-15 degrees. Backed off stop-nut and paralleled the TREs. Also got about 1/2 turn on the castellated nut on the drivers TRE.
I got 1/4-1/2 turn on engine-to-motor mount bolts on the drivers side. Never noticed any movement in the motor, so not sure this had much to do with it.
I got 1 full turn on the front passenger body mount.
Everything else in the suspension/steering/drive train was tight.
Also greased the rear drive shaft and tie rod ends.
The mass tightening/lubeing seems to have subdued the weight shift I was feeling. Fingers crossed, it stays gone. Thanks for all the suggestions gentleman, I wouldn't have thought to look at some of the things you've mentioned!
I noticed the passenger side tie rod end (1ton TRO with GM ends) was about misaligned from the drivers by 10-15 degrees. Backed off stop-nut and paralleled the TREs. Also got about 1/2 turn on the castellated nut on the drivers TRE.
I got 1/4-1/2 turn on engine-to-motor mount bolts on the drivers side. Never noticed any movement in the motor, so not sure this had much to do with it.
I got 1 full turn on the front passenger body mount.
Everything else in the suspension/steering/drive train was tight.
Also greased the rear drive shaft and tie rod ends.
The mass tightening/lubeing seems to have subdued the weight shift I was feeling. Fingers crossed, it stays gone. Thanks for all the suggestions gentleman, I wouldn't have thought to look at some of the things you've mentioned!
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I think a good portion of your fix was lubing the driveshaft.
If it comes back (and it very well might) put the video on two things.
One is the spring perches on the axle tubes, where the springs sit on them.
The second, and main culprit to my mind, is the driveshaft slip yoke. What happens sometimes is they stick (the same "stiction" they talk about in motorcycle front forks, and now diesel injectors) and when you accelerate it lets go with a thunk as the suspension compresses. It's not much, but it's hard enough with all that weight on it to make a good bump.
Check it out next time it does it.
Paul
If it comes back (and it very well might) put the video on two things.
One is the spring perches on the axle tubes, where the springs sit on them.
The second, and main culprit to my mind, is the driveshaft slip yoke. What happens sometimes is they stick (the same "stiction" they talk about in motorcycle front forks, and now diesel injectors) and when you accelerate it lets go with a thunk as the suspension compresses. It's not much, but it's hard enough with all that weight on it to make a good bump.
Check it out next time it does it.
Paul
