1980 17.5 Bigfoot Axle and Brakes

[COLIN R]

I bought a 1980 17.5 Bigfoot last spring and noticed 1 of my leaf springs is completely shot and my brakes don't work well because grease is getting in the drum brakes. I need to replace the axle and fix the brakes but I have a few questions.

1. Is the axle rated for 3500 lbs meaning I will need 2x 1750 lb leafs?
2. I need more ground clearance because I tow with a 4Runner. Can I rotate the axle which is not a straight axle but is offset so the centerline of the wheels is lower then the axle shaft? (currently the CL of the axle shaft is lower) This would give me huge clearance!
3.Does anyone know the specs on the bearings and oil seal of the drum brakes?

Regards!

[BobB]

You can order a new axle complete with brakes and bearings. Standens and Dexter are two brands I know of. Yours is a drop axle. You might consider a straight axle if you want to raise the trailer. An axle capacity of 3500# sounds about right. The other measurement is the distance between hub faces. A common brake size is 2-1/4 by 10". You might want to replace the springs as well. Fresh springs will raise the trailer some, maybe an inch. A new straight axle can be installed under the springs if you want the trailer higher. An axle can also be installed above the springs. Plan carefully before you buy! I would take it to an experienced trailer shop to have the axle replaced rather than trying to do it myself.

Edited to add photo of our trailer with a straight axle. Ours also has shocks and lowering spacers, which were added by the first owner. Here is a thread I saved:

http://www.fiberglassrv.com/forums/f...7cb-41542.html

[Borden]

Our boler axle is above the springs but your old axle looks to be offset and set below ours is not offset but center line of brake plate.
We have no extra spacer shown in above photo. Monroe makes a shock retro fit kit and have one of those purchased from local Napa dealer for our trailer; finished it looks like above with out the square tube spacer between spring and axle.

[Tony Nowak]

I couldn't add any more to what Bob says. His 2004 17 footer looks to be much higher than our 2003. Both with straight axles,15 inch wheels, Bob's with mods to account for difference. See the reply in Problem Solving for info on our axle replcament.
Tony

[Andrew Gibbens]

Originally Posted by COLIN R

Can I rotate the axle which is not a straight axle but is offset so the centerline of the wheels is lower then the axle shaft? (currently the CL of the axle shaft is lower) This would give me huge clearance!

Ooowww, turning a drop axle upside-down is a scary idea.

If you did that, the only thing holding the axle in position would be the friction in the U-bolts holding it to the springs. One big thump, like driving over a rock, might just rotate the axle backwards. With the axle suspended below the springs, it would also have a lot of leverage to twist the springs into an S-shape on braking.

[Steve C.]

Originally Posted by Andrew Gibbens

Ooowww, turning a drop axle upside-down is a scary idea.

If you did that, the only thing holding the axle in position would be the friction in the U-bolts holding it to the springs. One big thump, like driving over a rock, might just rotate the axle backwards. With the axle suspended below the springs, it would also have a lot of leverage to twist the springs into an S-shape on braking.

I strongly agree with Andrew - this would be extremely risky, as dropped axles are not designed to work upside down for exactly the reasons mentioned. Spring/U bolt failure and suspension collapse would likely be the eventual result.

In addition,you cannot simply rotate any trailer axle, dropped or not. All trailer tube axles are cambered (bent up in the middle) to maintain reasonable wheel camber under load. The result would be excessive negative camber (wheels leaning in at the top) and heavy wear on the inside of the tires.

What you have now is the original 3500lb 4" drop axle that has been converted from underslung to overslung (springs on top of the axle). If you need even more clearance, the best solution is to install an overslung straight axle as Bob recommended. Springs, bushings, shackles and bolts should be replaced as well. I think you will find it more economical to replace the complete assembly rather than buying individual parts.

I also noted in your photograph that there is no bump stop installed to prevent the springs from over deflection. Dexter recommends that one be installed on all overslung installations as spring bending or failure is possible. There should be no more than 2.5 -3" of available axle travel when loaded according to their engineers. There is a lot good information available at; http://www.dexteraxle.com/products___literature

If you are mechanically inclined, a complete spring/axle replacement is a pretty straightforward, simple bolt on job. Axle alignment will be required, but only involves loosening the U bolts and moving each side of the axle back and forth until the ends of the axle are equidistant from the centerline of the hitch. If you are at all uncertain about your abilities, have the axle professionally installed.

Steve.