I have a couple of full size Broncos. One is a 93 5.8l with 4 in procomp susp lift and 3 in body lift, the other a 90 5.8l with 6 in skyjacker stageII lift with 3 in body lift.

Both of these vehicles make an erratic banging noise whenever on the freeway on an incline above the 2000 rpm range. I can only describe the sound as being like when you are in a two lane freeway and are switching lanes hitting the road reflectors. It is freaking loud to outsiders as they jump or turn when I drive by and it makes this noise.

The sound is definately from the front, you can feel the floor boards by the firewall being bumped.

Both Broncos have new front ends, brakes, new Warn manual hubs, and every thing tightened. The engines are freshly tuned up, new tranny and tcase rebuild were just rebuilt by certified mechanics. I've also had the local gear and lift shops look at it to.

I don't think it's engine or exhaust related because the banging can't be controlled or reproduced on demand when on or off throttle. It is completely random, does not do it while driving in town, and does not do it all the time - it is infrequent - but enough to make me concerned.

What the heck is this noise? Anyone have any ideas or similiar experiences? Let me know if you need more detail and I will try to provide as much as I can, thanks for your help!

 

Radius arm bushings or even the mounting brackets perhaps? They are connected to the frame right below the floor boards there. When the bushings get bad enough you can feel them arms slap back a forth in the brackets every time you come to a stop and accelerate from one. It may just be that the nut hasn't been run down far enough and is allowing the arm to slip under the conditions you described. Thats about all I can think of in that area of the truck that could produce that much noise and not be something that you can instantly identify. Doesn't mean I'm right but it may be a place to start.

 

thanks for the quick reply greystreak.

Now I am really puzzled because I just had the radius arm busings replaced a few months ago with new urethane bushings from Energy Suspension.

One of my local shops thought the bushings may have been the reason too, but alas that did not cure it. The 93 Bronco is my daily driver that I've had for 6 months now and it was the first one of the 2 Broncos to make this noise.

I've owned the 93 Bronco for a coulpe of years and it is now starting to make the same identical noise too. Thanks for your help though.

Anyone else out there know what this might be and if it is serious? Thanks in advance.

 

One further question... do the trucks still behave the same with the hubs locked and the 4WD engaged?

 

Since the 93 is my daily driver, I don't have it in 4wheel (obviously) so I can't say for sure.

However, the 90 is my off-roader and it does make the noise when 4wheel is engaged ONLY when towing another vehicle on an incline though.

So, for instance, when I pull someone from the sand (I live my Pismo Beach dunes), and I have to pull them from the dunes to the beachfront for a distance, the truck will make that noise when going up an incline at about 25MPH with 2500 RPM or more. Once on flat surface the noise goes away.

Do you think it might be the Warn hubs? That would be a problem since they are only a few months old.

IF it is the hubs, how did I break them or rather what are things you shold not do to keep from breaking manual hubs?

Here's a pic of the 90 Bronco which is the beater: http://www.skywheelie.com/90_bronco.jpg

Here's a pic of the 90 Bronco which is the daily driver: http://www.skywheelie.com/93_bronco.jpg

Thanks for your help.

 

Those are pretty sweet rides. I spend some time up in Pismo and also have spent some time pulling out trucks and jeeps. I would have thought it'd be the Radius Arms also. I'd check the suspension bolts and the trans and motor mounts.

Good luck.

BTW I hate these kinds of problems.

Mike

 

bgblktruk - thanks.
I will go over the susp bolts and rad arms again. I usually make it a habit to tighten everything once a month - you gotta with off roading. I've done my fair share of pulling out suburbans, rangers, prerunners and even a jetta too. I've been trying to hook up with other Bronco owners at Pismo.

Email me (info@skywheeli.com) the next time you think you will hit Pismo - I will meet you there.

I will also let everyone know if I find the fix for this noise, thanks.

 

I have trouble believing its the hubs since the noise is generated whether they are engaged or not. Have you got front or rear sway bars still? Could be the front end getting light or even something further back sending the vibrations froward through the frame. (I had what I thought was t-case trouble a couple years back and it turned out to be a broken axle pivot mount... sound and all vibrations will travel through steel all over the place). Sway bar could be popping or shifting when the front axle gets some weight pulled off it or the rear is under hard torque. Again, I'm just guessing here trying to come up with something that would do this repeatedly and not show some outward sign of serious damage by now.

 

bgblktruk - got your PM, thanks sorry to hear about your last trip to Pismo.

Greystreak - both sway bars are not on the vehicle. I ran the 90 Bronco hard this weekend and got it to make the noise. I'm also suspecting its the engine now. If I floor it getting onto the freeway, by the time I reach 65mph it will start the popping and backing sound and for the rest of the trip will be weak going up inclines or grades even with OD off.

As for off-road, it will only start popping and banging when I put a real load going up hill for a long period of time. I am tempted to record the sound next time and take it to a mechanic - it REALLY loud!

I will ook at the axle pivot mounts, thanks.

 

I think its a motor mount or a transmission mount. I had the same problem. Just a guess

Thanks

Mike

 

You know, you would be on the money there. I can see the motor mounts look pretty worn. Can I use these below (copy aned paste the link if it does not work):

http://broncograveyard.com/bronco?PH...&Submit=+Go%21+

Part # <!--StartFragment --> # 30505 at Bronco Graveyard. If this works I will order and install, thanks!

 

I don't see why not. They are substantially more expensive but if they are stronger as they say it might be worth it. I'd also suggest that if they are bad check the transmounts cause they then take the stress of both.

Mike

 

Will do - I will report my findings in a few weeks, thanks.