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bout to burn a bucking bronco!!

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
...if it were mine! here's some history.

im working on this '70 bronco for a bud. it came to me because it had a cracked axle tube. the PO made some ladder bars, welded to the axle and hard mounted to the frame! one on each side, not allowing axle to move at all. he got another housing from someone and i began swapping things out. first find...both rear spring were broke! had to find more springs. got new shocks, heavy duty u-bolt kit, stock springs, 2.5" lift blocks, all new rear brakes.

moving on...once all that was done, took it for a drive. couldnt hardly drive it, bucking so bad, i asked about the clutch. he told me he thinks he burned up the clutch because he cant use first gear. (3 speed in floor) i checked the linkage and tried again, 1st still popped out immediately. he had another 3sp that came with the truck, but it was a 2wd drive tranny. so he found another 3sp, bought a new clutch and resurfaced the fly wheel. while doing this swap, i found the T shift tcase had bad front output bearings and clunking. I had a tcase laying around, so i told him we would use mine. swapped it all in with a better used james duff shifter. everything is smooth...

however, this damn bucking crap is still there!!!! if i apply any throttle, i feel like the bronco is going to fold /break in half!!! the return spring on the throttle wasnt even working right, reworked it and now have a nice 500-600rpm idle( which helps) but its driving me crazy. so ive had the hood up and he was making the truck buck in first-i was making sure the motor mounts were good and they are/zero movement. i even installed the cheaper duff traction bars that mount on top of the springs today...hoping to see some results. (he already purchased these months ago, so i figured it couldnt hurt.
of everything ive had to do to this bronco, the only thing that worries me, is the rear drive shaft. fully compress and i can barely install it to the 9". while doing the rear axle(a month or so ago) i completely rebuilt the drive shaft. please take a look at the rear springs, im sure they are installed correctly, been a while since ive installed stock ones. mostly install aftermarket lifted springs, with military wraps toward the front. while watching the motor mounts, i also watched the rear axle, each time he released the clutch, the axle would rotate upwards, but only a .5" or so...not like its shooting way up. i dont want to just throw money at this...but im about lost...really need some other insight. here are some pics
 

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clarrance

Bronco Guru
Joined
Mar 3, 2005
Messages
2,674
I don't know if the helps or not, but the springs look very weak. There is no arch to them at all in the picture. If the spring tries to wrap up easily because its weak, then the driveshaft can't move because its already collapsed maybe that's the problem.
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
im on the same page as you, i debating to swap in another stock drive shaft to see if it fits better with more slip yoke. as you can see, its compressed now as it sits. weird thing.. owner says with everything going on, it never bucked like this until axle and springs were swapped. we also noticed the truck is sitting 1" lower in the back now...so i know the springs are softer.
 

Deano

Bronco Guru
Joined
Jan 9, 2010
Messages
1,183
Check bushings in the Z bar and if there is movement in the door post/dash area. Check trans bushings to. Week springs don't help on axle wrap that's for sure any combination of these makes them hard to pull out
 

BRONCROB

Bronco Guru
Joined
Nov 24, 2010
Messages
1,613
Loc.
WISNER LA.
I would think dshaft was binding up too.Probably too long causing the joints to bind and the bucking.May try the front one out back if it will fit any better.
 

JSBX

Contributor
Sr. Member
Joined
Mar 10, 2010
Messages
616
Pull the back drive shaft and drive it in 4 high. This should let you know if it is the drive shaft or it could be only part of the problem.
 

NGABronco

Contributor
Bronco Guru
Joined
Feb 4, 2007
Messages
7,390
Loc.
N. GA now South Carolina
Chuck, those blocks look like they're rotating the pinion an awful lot????%)%)
With weak springs and that much rotation, it might be torquing up too high???
Good luck!!
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
Ok I have spent the last 2 hrs swapping drive shafts, parts ,etc to make one the right length...with no luck. However I left the rear out and drove it. A tiny bit of shaking in rev...very mild. But none in first now. I'm convinced the rear was completely compressed and causing this. I was able to launch it with only front spinning...no buckin. I think I still have spare shafts packed in my 77 from a wheeling trip. Will try that after dinner
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
Do not know the condition of front shaft, and honestly...don't care at this point. I'll post up results soon. Thanks for responding guys, it helps
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
Ok I grabbed a stock rear shaft. Won't fit, just like what I took out!! I must have installed the leafs backwards!! But it's the only thing making sense...no problem til leafs installed. No drive shaft is tight. Please look at the spring eyes and see if these are right. I'm going nuts here. I even compared to another bronco sitting here . It's stock leafs with blocks
c41fe83768cd1a24d10e5e2a2472704e.jpg
2a261c6565298652ed055ee504b59b61.jpg
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
heres a pic i found from when i was removing all the old stuff...looks like the new leafs are installed right.
egary5yt.jpg
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
That's not making sense, I saw a post in another thread saying these are in right, a couple Broncos have leafs in this way...I need some pics or proof.
 

BRONCROB

Bronco Guru
Joined
Nov 24, 2010
Messages
1,613
Loc.
WISNER LA.
Yes, they are on wrong. BRONCROB, yours are backwards also. Get a new correct length drive shaft, you'll need it. Just as important as a good set of tires.

Mark

Must be Fords fault,I haven't changed them:DMine work fine.You made me double check my factory ser. manual and it agrees.Damn you:D:D
 
OP
OP
blazinchuck

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
Ok but if so I thought each spring eye used different size bolts...or are they the same? I really don't wanna do all this crap again. You can see the before pic and after pic with this bronco's springs. Like I said, there is another bronco here with them the same way
 

BRONCROB

Bronco Guru
Joined
Nov 24, 2010
Messages
1,613
Loc.
WISNER LA.
Wrong, yours are on backwards.

Are you using yours as an example or what?I am by no means an expert on rear springs but how are you certain yours are right?Mine work fine but now you are making me second guess my original setup.
 
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