GVWR woes!

[GoldenGate]

I've been off my skoolie conversion game for a bit due to school/holidays/beer etc, but as I begin to get going again, I now feel that if I build everything that I'm planning on building, I MAY end up over the GVWR when loaded.

The GVWR as listed on the Ford sticker is 10,000. The sticker from Gibbs bus sales in Oxnard, CA lists the curb at 7,640 dry, leaving me 2,360+/- lbs to work with.

Since this bus is turning out to be more of a party bus sort of thing, passengers will make up a significant weight. WORST case scenario I could see this thing lugging around maybe 1,800lbs of passengers, which leaves me 560lbs to add to the dry weight, give or take.

I have a battery bank of 2 group 27 deep cycles, and a little weight in electronics like my 32" LCD TV, stereo stuff, lighting etc.
Seating will most likely be 4-6 re-upholstered bench seats from some sort of truck, like a Chevy 1500 or something else that's ubiquitous in junk yards.
But what I think may be the "coup de grâce" is my plan to build a roof deck as well as a rear platform to accommodate a small staircase/latter. I'll build it as light as I safely can (expanded metal woo!), but in all honesty I have no idea what something like this might weigh. In the off chance that it tips the scales at over 10,000,
am I worrying too much? Is it really THAT unsafe if I go over my GVWR on occasion? I feel like it may be one of those things that they underrate for safety, but in all honesty I've never had any experience with hauling or big trucks, all my cars prior have been small or performance oriented.

 

[the_experience03]

As long as you have paid the proper tax for a given GVWR the government is going to leave you alone as long as 1. You have no exceeded your tire ratings and 2. You have not exceeded their axle weight ratings (20k on the rear I believe).

You are going to have the biggest issue with the tires I think. The rear axle is going to handle the load fine, but 16 or 16.5's might not cut it. Look into your actual rear axle weight ratio. You might need to swap in some 19.5's. That's a starting point anyway.

 

[Jarlaxle]

DO NOT EXCEED THE GVWR ON THIS BUS! The axle ratings ARE the GVWR: running max weight means BOTH axles are at 100% capacity. It also mteans the TIRES are at 100% capacity. GVWR should be 11,500 on an E-350 DRW...10,000 is low.

 

[the_experience03]

I'm going to play devil's advocate here and say the axle ratings and the GVWR are not necessarily directly related to each other. Very often you can add up the GAWR and it will be substantially higher than the GVWR. GVWR is a function of many things including component strength, but also emissions requirements as they are often based on GVWR and taxation purposes. A fine example I recently worked on was a 1999 C2500 (old body style). It had a FGAWR of 4100 lbs and a RGAWR of 6000 lbs on a 14 bolt semi float rear end. The GVWR was only 8600 lbs. Now we can take that same rear axle and look at my '91 C2500 and it only has a RGAWR of 4800 lbs, but it also only came from the factory with 6 ply LT tires on it, the limiting factor in that combination.

It's a guessing game, especially when it comes to figuring out the engineer's margin of safety on something, but TYPICALLY the components far exceed the demands laid out be the ratings applied at the factory.

*edit* What rear axle do those cutaway vans have? If it's a 10.5 Sterling I think any more than the 10k-11.5k GVWR might be pushing it, but if it has a Dana 110 or 135 monster under the back he would have lots of room to play with on that end of things. The transmission would most likely be a 4R70 though, wouldn't it? That scares me...a lot.

 

[GoldenGate]

Sorry, I meant to post the axle ratings in my original post. The inconsistencies between the combined axle ratings and the 10,000gvw are actually what got me confused in the first place.

First off, the rear axle is for sure a Dana 70, 4.10 non-limited slip.

Another point of confusion is that the Ford sticker and the sticker from the bus dealer both list DIFFERENT axle ratings, though they BOTH list the gvwr as only 10,000.

-Ford lists the front GAWR at 3900 and the rear at 7200.
-Gibbs bus sales rates the front GAWR at 4600 and the rear at 7800.
Is it safe to assume that Ford's rating are correct since they're the ones who actually manufactured the chassis? Is it possible that Gibbs did some sort of dealer modification that increased the GAWR?

Regardless of which tag is right, the sum of both axle ratings would be either 11,100 or 12,400...both significantly higher than 10,000 which is why I originally assumed that it was the brakes or suspension that was the weak point.

As far as the tires go, the rears are 16's that indicate on the sidewall that their maximum load is 2470 in dually configuration at 80psi. The Ford sticker lists psi at only 55 for the rear though, and that's always seemed a little low so I keep them higher. Should I run then at closer to 80psi? Would that mean that at 80psi, I could TECHNICALLY load the 4 rear tires with 9880lbs?


Oh and about the trans: Don't be scared, its not a 4R70. Its an E4OD...be TERRIFIED. At this point I feel like the trans is really my weak point throughout. I hear an at545 will mate up nicely with my 7.3, given I get a hold of the correct bell housing. Is this true?

Thanks for all your help guys!

 

[Jarlaxle]

Don't go over 10K. The limit is NOT the axles. It's quite likely the FRAME, especially if it was stretched (very common on shuttle buses).

Oh and about the trans: Don't be scared, its not a 4R70. Its an E4OD...be TERRIFIED. At this point I feel like the trans is really my weak point throughout. I hear an at545 will mate up nicely with my 7.3, given I get a hold of the correct bell housing. Is this true?

Well, yeah, plenty of 7.3's came with AT545's...but why would you want to swap a lockup OD trans for a non-lockup, non-OD slushpump? (And the AT545 may not clear the trans tunnel.) That will also mean 50MPH is about it, considering the typical 4.10 axle in these vans. It's almost certainly been rebuilt (and probably upgraded to 4R100 specs when it was), should be good for another 100K. Add a BIG cooler & a trans temp gauge, and DON'T LET IT HUNT IN AND OUT OF OVERDRIVE!

 

[GoldenGate]

Well that sucks about the 10,000gvw

The E4OD has always been sloppy, it has a hard 1-2 shift, sometimes it gets stuck in 2nd or 3rd if I have to stop abruptly etc. It may last a while but in the case that it goes out, I'd be more interested in something a little more hefty. It actually had dual trans coolers as it so I'm not worried about cooling. I've just never heard great things about E4OD's

 

[Jarlaxle]

I'd have a good trans shop (not scAAMCO) look at it...might need something minor, like a sensor. Also, how old is the fluid? And is it the RIGHT fluid? Not sure what year Ford switched to Mercon V.

You still need a trans temp gauge.

 

[GoldenGate]

Oh yea...the fluid. It takes Mercon V, I know that much for sure. The thing though is that the fluid is burnt. I've heard that once the fluid is burnt, its best to just change the filter, but keep the fluid because the solvency of new fluid will mess up something that was burnt in the trans when the fluid burnt. Don't know how much veracity there is behind that but I don't want to chance grenading the trans until I have something concrete lined up. Know anything about that?

 

[Jarlaxle]

Change the filter, top up the trans with fresh ATF.

Might be cooked.

 

[GoldenGate]

I'm about 75% sure its cooked. Been counting the minutes until it totally craps out...I'm prepared to drop the money on a rebuilt E4OD when (looks like they run about 900-1300 in my area) but if there's something out there that would be a better option, let me know.

 

[Jarlaxle]

An E4OD rebuilt & upgraded to 4R100 specs.