bout to burn a bucking bronco!!

[blazinchuck]

wow, if things couldnt get any worse...had a friend come by to help check. my bronco (for whatever dang reason) has a 92.5" wheel base. Doug's 76 has 93" wb. Ryan's bronco(the one im working on) has a 90.5" on the pass side!!! and a 91.5" on the dr side!!! I just dont understand, the frame looks good, no signs of wrecks. also just got another set of springs with a add-a-leaf...so they have a great arch to them and i will install them soon.only thing i can figure is something is up with the blocks. the radius arms look correct(no worn out bushings) both shackles look like they are standing straight up...i thought maybe one would be forward, and one back...but its not. also, the damn axle housing is leaking around the rear cover from factory weld area...ugh!!!

 

[BRONCROB]

I would just go ahead and burn the sob,be better than having yourself a stroke.Oh and factory wheelbase should be 92"

 

[blazinchuck]

You're correct broncrob, I thought it was 93. That makes me feel better, I have duff radius arms so that can explain mine at 92.5, but Doug's at 93 is weird too lol. I should burn it lmao....burn them all haha

 

[BROwN COw]

I owe Rob money! Don't listen to him, Chuck! (Just kidding, Rob)
If anyone was in doubt, Chuck is an amazing dude for doing what he does for Bronco brothers. P.S. This is the storage locker Bronco from last year that he's working on. Now I guess we know why it was parked for 9 years...

 

[blazinchuck]

No worries Ryan, I decided to do something that makes me feel better

 

[dao1980]

Some times firewall flex can cause the clutch to oscillate between engaging and disengaging when starting off.

It can cause one hell of a "bucking" situation if the firewall flex is really bad.

 

[DirtDonk]

Yeah, and it's still sounding like a clutch issue to me too. Those other things aren't making it any better, but the clutch is where it's probably starting the cycle.

Along with other modern wonders, I bet it's not impossible to get a bad clutch right out of the box. Nor is it impossible for a shop to do a poor job on the resurfacing, OR, for that matter, is it not impossible for a flywheel to be so bad that resurfacing doesn't fix it.
I've never had that happen, and never known anyone that it's happened to, but I doubt it's impossible with a Bronco!

When both of my clutches went out they acted like yours to a point. But when I replaced my original clutch with the new one and "thought" that the flywheel looked just fine and didn't want to pay to have it resurfaced, the truck was literally undrivable even in low range.
When both clutches were old and chattery and made the Bronco buck though, using low range would completely take care of the issue. Clutch engagement is so much less of an issue in low, that it just can't quite build up that harmonic two-step dance routine.

Not to stop you from doing all of your other checks, but you can't ignore the new clutch just because it's new either.

Good luck. You're certainly running down the list of possibilities.
Dao has a good suggestion of the firewall flex and someone previously mentioned linkage issues. Either of which can effect clutch smoothness. But the severity of your issue could be more than those could do maybe.

Hey, maybe it's just another one of those "all of the above" Bronco issues!%)

Paul

 

[dao1980]

I had to run a brace down and across my firewall to get my clutch to stop acting like it was dealing with a warped pressure plate. (Which after much and repeated inspection, it wasn't.)

The best way to check your firewall flex is to (with the hood up) have someone press the clutch in while you look (from the driver's side) across the top of the firewall.

Mine was so bad you could see flexing clear across to the passenger side.

I had gotten used to driving it without needing to slip the clutch any, but no one else could even get it to move without starting a terrible bucking that seemed like it was going to destroy the truck.

Even the guys at the local 4X4 shop couldn't move it around the parking lot and stared at me in embarrassment that they couldn't move my Bronco.

I guess I had just adapted to how it needed to be handled (no revs/no dillydally getting the clutch engaged) starting off, over the long time it took to get so dern bad.

My good buddy Bobby the Bronco guru made me a little plate that he bolted and welded to the top side of the firewall and then ran a tubular brace down to the cage mount point to stiffen everything up.

Now I can just about burn the tires by revving up and easing into and out of the clutch.
It's probably not very good for everything else to do that with 37's but hey, fun is fun!

Anyways that has been my experience in dealing with the horrendous bucking issue.

 

[asinor]

I think your l/r wheelbase issues are the worn springs and blocks. Removing the rear shaft solved the problem so its not a clutch issue. It has to be in the geometry of the rear suspension.

 

[DirtDonk]

Unfortunately, I don't think that having the front work better completely rules out the clutch just yet.
The reason is axle wrap working with a poor clutch. The front just flat doesn't have any, since the axle is semi-rigidly clamped into the radius arms. The rear on the other hand has all sorts of axle wrap/spring twist, which can get even worse with aftermarket springs.

That alone could conceivably make enough of a difference between the front and rear to negate the results from 100% down to maybe 50% or less. Without the axle-wrap in the equation, the harmonic that causes the extreme shuddering is harder to achieve.

Paul

 

[englewoodcowboy]

After reading through I think you definitely have a problem caused by a combination of things. You have eliminated the drive shaft bind, now you are left with weak springs and as clarrance mentioned, the 3 finger clutch. I have a sneaking suspicion replacing the clutch to a more modern one will help some but until the rear springs are replaced you are still fighting a worn out variable.

 

[blazinchuck]

time to bring this back to the top...we have success! i first took a long break from this truck, too many things not adding up. so starting yesterday, I ripped everything out again( tranny,bellhousing,tcase,axle,springs, etc. a new flywheel was ordered, but after removing the existing flywheel..we quickly knew it was wrong. the new one was 157 tooth, we needed a 164. however, the new 164 we got later in the day had different bolt pattern for the pressure plate. so Ryan ran to another auto store for a diaphragm style that would bolt up right.

as for the axle, i found the lift blocks to be some of the wheel base issues. the center holes were deformed(where the leaf center pin goes and the cast center pin went into axle perch). got some better blocks today, from what i can tell the wheel base seems closer to stock...but not perfect- 91.5"...on both sides!! still able to use a stock rear drive shaft.

now, back to the main reason for the thread...BUCKIN! i really wanted to change just the flywheel, so i could zero in on exactly what the problem was. since we could not run the 3 finger with the new 164 tooth flwheel...i guess we'll have to agree that everyone that said 3 finger and those who said flywheel were all correct lol. today we drove it all over! launched it, soft easy driving, hard driving, etc...it drove great!! for now, the bronco is right...as it should be. sorry to leave everyone hanging on this for a while.

 

[BROwN COw]

Update: She lives! This weekend Chuck replaced the leaf springs, blocks, clutch, and flywheel. (Went with the diaphragm clutch). The Bronco (now dubbed The Albatross) no longer attempts to violently shake itself to pieces when starting out in first gear. It shifts smoothly, and drives as it should. Thanks Chuck!

 

[NGABronco]

Hey Congrats to you both!!!! I'm just glad Chuck didn't drag out that gas powered chop saw and start cutting!!!!

Glad it all worked out!!!;D;D;D

 

[chuzie]

Bout damn time. Now get that piece of junk out of my spot!

 

[BROwN COw]

Ben, Chuck actually did start a blaze under the gas tank yesterday. He claims it was unintentional as his whole shop would have exploded with my Bronco, but then again, his name is Blazin' Chuck...

 

[Crawdad]

I had a set of NIP (new in package) 2" lift blocks you could have. I was going to keep the ubolts for my build. Glad you got that ole gal running good, hate to see it go back in storage! ��