[Jumpster]

Hi folks, looking for a little insight here. Am thinking about getting a Promaster to use as camping vehicle. Have heard various complaints about the rear axle hanging low, and though I realize it is actually the same clearance as the front, I wonder about an easy fix to get a couple inches extra in the middle. The rear axle is a square or rectangular steel tube from what I can see, and I am wondering if there is a bit more than 2” of airspace on top of it in the middle (obviously not at the stops) when the suspension bottoms out. If so then one could weld a 2x2 steel tube to the top of the existing axle tube from leaf spring bracket to leaf spring bracket, then cut out the middle of the axle tube leaving 3 or 4” of overlap – and maybe have steel side plates reinforcing. But of course this could only work if there is clearance for it, and I can’t tell from photos I have seen if there is or not. It looks like, from photos I have seen, that the exhaust pipe is the tightest spot. So can someone look under theirs and see what you think? If I get one it would be at most a 136, and probably low roof. Thanks for your help!

 

[Obrian]

I was thinking the exact same thing. 10.5" I between the rear beam and body. 3" between the leaf spring and bump stop, of course that doesn't include bump stop compression. Exhaust is going to need to be rerouted, probably outlet in front of the rear tires. If I still had all my fab equipment and shop I would have already done it, but suburban southern California living makes these projects hard. Good luck

 

[phil]

Anything is possible, I would ask a shop that does rear axle mods, and use a junk yard axle, keeping the original in case you sell the van.

http://timbren.com/axle-less/

I looked into this, but for what I use the van for I found little value in it.

 

[Jumpster]

I was thinking the exact same thing. 10.5" I between the rear beam and body. 3" between the leaf spring and bump stop, of course that doesn't include bump stop compression. Exhaust is going to need to be rerouted, probably outlet in front of the rear tires. If I still had all my fab equipment and shop I would have already done it, but suburban southern California living makes these projects hard. Good luck

Thanks O'Brian - - if it's not too much to ask for more numbers, how much is there between axle tube and exhaust pipe?

 

[Streetdoctor]

If you have the same clearance in the front, why?

 

[Jumpster]

If you have the same clearance in the front, why?

There are fixes for the front - Spaccers, for instance - but I haven't seen anything for the rear so far.

 

[Obrian]

Thanks O'Brian - - if it's not too much to ask for more numbers, how much is there between axle tube and exhaust pipe?

My van is parked on a slanted driveway right now so I may be off a little but six inches is what I measured.

 

[Obrian]

If you have the same clearance in the front, why?

I have 7.5" in the rear and 10.5" in the front. That's with 245/75 tires and a little re adjusting to the front suspension. I've been stuck in the desert because of that low rear beam. A few more inches back there would be awesome. And it would look so much better without that stupid low beam back there.

 

[Jumpster]

My van is parked on a slanted driveway right now so I may be off a little but six inches is what I measured.

Thanks. So that makes it look like, if you put a 2x2 square steel tube on top of the existing axle, that leaves 4", and with 3" to the bump stop, that leaves 1" of bump stop compression before contact with the exhaust. Probably too tight, though tough to know how much compression one would get out of those bump stops.
Am I right in assuming that before it gets to the axle, the exhaust is done with mufflers/converters and is just a pipe? So that diverting it before the axle might not be too big a deal?
And if the exhaust was out of the way, there is nothing else in the way?

 

[trhoppe]

Since you're suggesting to just cut/weld up the middle without messing with the springs, shocks, bumpstops, etc, this would seem to be really easy with a torch, welder and some square tubing and a few 90 degree exhaust bends to reroute the exhaust. Just cut out the middle and weld on a new square tube with a bit of overlap on each side.

Now that I read this and think about it, this might be a super worthwhile mod. I have a pretty great ride height in the back now, and will be installing a generic 1" front rubber spacer (Same thing as Speccer, but $15 on Amazon). The way it sits now, with my 245/45/17s, the front lift, and a rear axle that's 4" higher would be really nice.

 

[Swoop]

The more I think about the clearance issue with the rear axle, the more I wonder why it wasn't designed to have more clearance. It seems like it would have only required a little bit of engineering and a few minor changes in the fabrication process. I guess it would have added a few dollars to the MSRP without adding conspicuous sales candy.

 

[Brian P]

The more I think about the clearance issue with the rear axle, the more I wonder why it wasn't designed to have more clearance. It seems like it would have only required a little bit of engineering and a few minor changes in the fabrication process. I guess it would have added a few dollars to the MSRP without adding conspicuous sales candy.

Cost ... nothing more. (On top of that, this vehicle was never designed to be an off-road vehicle, so the need to pass over large obstructions would not have been on the design criteria.)

The existing axle is a fabricated structure. Piece of straight tube ... plate welded onto each end ... few reinforcing braces on each end ... few extra bits to locate it on the springs and give a place for the shocks to attach. As simple and low-cost as possible. Leaf spring beam axle is not rocket science.

Rather than fabricating a new beam (which seems to me to be a recipe for alignment trouble), I'd be tempted to see what's involved in making new stub axles and then simply weld those to a straight tubular axle without using the stock dropped-beam arrangement. The leaf springs could go under the axle instead of above, you can play around with shackle configuration if needed (not rocket science) and bump stops can be put someplace else instead of straight on top of the axle. Exhaust would have to be re-routed. At least in my area, the exhaust is legally required to exit behind the passenger compartment, so it might technically be a violation to do it otherwise, but on modern vehicles with very clean-burning engines there should be so little nastiness left in the exhaust that it shouldn't be an issue.

 

[heaphy]

"Since you're suggesting to just cut/weld up the middle without messing with the springs, shocks, bumpstops, etc, this would seem to be really easy with a torch, welder and some square tubing and a few 90 degree exhaust bends to reroute the exhaust. Just cut out the middle and weld on a new square tube with a bit of overlap on each side"


I have been thinking about this for quite awhile and I should draw up my ideas on this and post!

 

[Swoop]

Cost ... nothing more.

When Fiat hires me as a designer/engineer , here is the modification I'll propose. Three bends in the axle tube will provide 2 or 3 more inches of clearance in the middle, where it matters most on rocky, rutted dirt roads. The rest of the fabrication process could be as-is. That shouldn't add very much to the cost. (But, yeah, I know, every penny counts.)

 

[mloganusda]

On my Winnebago Trend MH, the exhaust exits in front of the left rear wheel. You may have to enlarge to see the exhaust portion.

MLogan
2017 Trend (2016 cab)
Smyrna, TN

 

[Chance]

Travatos are done the same way with exhaust out the side. I think that's for generator clearance. Additionally, Ducatos had exhaust exit behind driver's door for years -- not sure if latest model year is still the same.

 

[Chance]

When Fiat hires me as a designer/engineer , here is the modification I'll propose. ....cut....

That's the way many heavy duty trucks' front axles are done, expect they curve down instead of up in order to provide greater clearance to engine oil pan located above front axle.

 

[Obrian]

I'm sure you guys have seen it, but here is how the factory does it. It would probably take me halph a day to cut a square tube, weld it on top of the existing axel beam, cut the middle section out of the stock beam and fab some reinforcement plates for piece of mind. All without even pulling the rear tires off. There shouldn't be any change in alignment or anything else. Seems like a fun progect.

 

[Chance]

....cut....

Rather than fabricating a new beam (which seems to me to be a recipe for alignment trouble), I'd be tempted to see what's involved in making new stub axles and then simply weld those to a straight tubular axle without using the stock dropped-beam arrangement. The leaf springs could go under the axle instead of above, you can play around with shackle configuration if needed (not rocket science) and bump stops can be put someplace else instead of straight on top of the axle. Exhaust would have to be re-routed. .....cut....

Have you looked at factory hubs to see if they are not "bolted" to plates at end of beam? I don't have a PM to inspect, but recall wheel ends may be bolted to axle assembly. If so, it may be possible to fabricate an adaptor to move wheel centerline down relative to axle beam (which would raise entire axle), and then move beam axle above leaf springs to lower van back down.

Others have relocated axle above springs so that part is already tested. Axle to frame clearance should be the same. Again, I'm not sure if this would work because I don't have a van to inspect. May be worth looking at as a possibility.

 

[phil]

They show 2 types of rear axles, not sure what the other one goes to.

https://www.stevewhiteparts.com/auto-parts/2016/ram/promaster-1500/base-trim/3-6l-v6-flex-engine/rear-suspension-cat/rear-suspension-scat