18' Axles *DO* Fail - Replace Yours ASAP

[zero]

Well the fake dually was not a toyota item. They were all installed by the rv manufacturers and the page in the axle facts is from National RV the maker of the Dolphin. It amounts to them admintting they were at fault. Not CYA by any means

Linda S

I assume that Toyota was selling new trucks to RV makers knowing they were not really suited for the job. Whether or not Toyota knew about, authorized, ignored, "fake duallies", the company was obviously partly responsible for their existence. I assume that's why they participated in furnishing new axles to RV owners and later pulled out of the market.

GM went through similar problems with the Blazer Chalet and GMC Casa Grande. They both could be easily loaded beyond 6000 pounds and only had 10 or 12 bolt "1/2 ton" axles in them. They have durabilty equal to what Toyota semi-floaters have. GM agreed to stop allowing any RV bodies on any Blazers or Jimmys and to install warning sticker stating such. I swapped a 14 bolt, 9.5" semi-floater into mine. Not as good as a full-floater but good enough with a 6000 lb. max load rating.

[zero]

Some updated specs on my 1987 four-cylinder dually box truck. I'd forgotten that the GAWRs were recertified by the company that put the box on it. They give the front GAWR as 2660 lbs. and rear GAWR as 2780 lbs. I have no idea what was involved in that recertification.

[Totem]

wow, full floating axle and dual wheels only give an extra 120 lbs?

[zero]

Again . . GAWRs do not always reflect the max safe weight limit for a rear axle assembly. It takes into account vehicle handling, brakes, springs, tires, type of use, etc.

I regard it safe to assume a standard Toyota semi-floater rear axle assembly can live a long life carrying 3300-3600 lbs. and can carry 5000 lbs. without immediate failure. A Toyota full-floater can give long service carrying 4000-5500 lbs. and would probably need 7000-8000 lbs on it to suddenly fail. I regard that as a huge difference.

[DCGonzo1]

I assume that Toyota was selling new trucks to RV makers knowing they were not really suited for the job. Whether or not Toyota knew about, authorized, ignored, "fake duallies", the company was obviously partly responsible for their existence. I assume that's why they participated in furnishing new axles to RV owners and later pulled out of the market.

GM went through similar problems with the Blazer Chalet and GMC Casa Grande. They both could be easily loaded beyond 6000 pounds and only had 10 or 12 bolt "1/2 ton" axles in them. They have durabilty equal to what Toyota semi-floaters have. GM agreed to stop allowing any RV bodies on any Blazers or Jimmys and to install warning sticker stating such. I swapped a 14 bolt, 9.5" semi-floater into mine. Not as good as a full-floater but good enough with a 6000 lb. max load rating.

I'd like to know more about this axle you installed, is it posted?

[zero]

I'd like to know more about this axle you installed, is it posted?

I can post photos and specs if you want - but there isn't much to see. The GM 10 bolt and 12 bolt semi-floating axles have exactly the same weight carry capacity. I.e. the same diameter axles riding directly in roller bearings. The 14 bolt semi-floating axle has larger axles and larger roller bearings and for many GMs - it is a direct bolt-in swap for the smaller axles. That's what makes it popular. They can be found in 3/4 ton Suburbans with 8 lug, 16" wheels and also in some later "HD" 1/2 tons and "LD" 3/4 ton trucks with various lug configurations. The 14 bolt semi-floater has a 9.5" ring gear and a 6000 lb. max. rating which is pretty good. On my 86 Blazer - it originally had a 10 bolt rear with 6 lug/15" wheels. I swapped in a 14 bolt semi-floater from an 89 GMC 3/4 ton Suburban with 8 lug/16" wheels. I also took the 8 lug front hubs from that Suburban and the bigger JD7 brakes and put them on the Blazer. So now the Blazer has 3/4 ton running gear, 3/4 ton JD7 brakes, and matching 8 lug/16" wheels all around. This RV I'm posting photos of is my 86 diesel Blazer with a Hallmark RV body with pop-up roof. I also have two Blazer diesel Chalets (made by Chinook). The Hallmark was made in Colorado and is pretty scarce.

I started out with steel 15:" six lug wheels. Then got some nice aluminum mags. But after converting to 3/4 ton running gear and 8 lug wheels - I'm back to steel wheels. I'm too cheap to pay big bucks for new wheels. I'l get some used sometime. Maybe when my Ford F250 dies. It has real nice aluminum 8 lug 16" wheels.

[linda s]

In regard to specs. Winnebago with their Warrior gave a GAWR for the rear at 3,750 lbs and front GAWR at 2,050 lbs.. My 1987 dually Toyota box truck also has a GAWR for the rear at 3,750 lbs.

Again though - GAWR ratings are not just for the max weight the axle itself can sustain. It also factors in tires, springs, brakes, etc.

OK I don't want to argue about this I just want to know why. I found the winnebago specs for a 1994 winnie which would be a 93 chassis I think and the GAWR was 4400 lbs. Way more than mine and yours. So could the v6 axle be stronger?

Linda S

[WME]

Remember that with the fake duallys and with single wheels on the 1/2 ton axle the axle takes the full weight (via the single bearing) and the power. The 1 ton axle has TWO bearings at each hub that carry the weight. The axle just handles the power.

[zero]

OK I don't want to argue about this I just want to know why. I found the winnebago specs for a 1994 winnie which would be a 93 chassis I think and the GAWR was 4400 lbs. Way more than mine and yours. So could the v6 axle be stronger?

Linda S

Specs from Winnebago on their 20' Toyota with a 2.4 show - GAWR front as 2,050 lbs. GAWR rear as 3,750 lbs. Total GVWR as 5,500 lbs.

Actual weight on scale (I suspect without passengers) - front - 1800 lbs. rear - 3,060 lbs., total weight - 4,860 lbs.

I doubt anyone on this forum can say for sure what any posted specs are based on, specifically. GAWR specs are NOT just about the weight the axle-assembly itself can handle. It's about how much weight the manufacturer is willing to warranty. A company can take a 10,000 lb. axle and rate it as 2000 lbs. if they want.

When the actual makers of rear-axles post specs (not the company making the vehicles they are used in) - even then the ratings are often conservative. If a company states an axle-assembly has a max rating of 6000 lbs. it might mean it can actually carry 10,000 lbs. for short periods of time. You will be hard pressed to find specs anywhere that show at what weight an axle-assembly actually self-destructs. Posted ratings are usually projections of what an axle can carry throughout a long period of time. Sometimes 500,000 miles.

When it comes to heavy trucks and engines - there is a "B" rating system. No such thing for rear axles. A engine - like a Dodge-Cummins 5.9 - is B10 rated for 350,000 miles. That means that endurance tests were done and 10% of the engines tested failed before reaching 350,000 miles with good maintenance and heavy use. It also means 90% DID make it with no major repairs.

I still don't understand the question about V6 rear axles. They are beefed up in the center-section where the ring & pinion and differential are. That allows more engine torque and horsepower and twisting force. It has nothing to do with carrying more weight. "Propelling" more weight, yes. The external housing is also stronger which does provide less flex. Again, it has nothing to do with the weight-bearing problem in small RVs. Axles carry a rating for how much weight then can bear and roll down the road safely. They also carry a max-torque rating that projects how much engine power or twisting power they can handle. The latter is what your V6 axles are about. It is also a spec you don't see often. The 14 bolt GM rear-axle assembly in my Blazer has a 5000 pound-foot torque rating.

The Toyota RVs that had axle problems had 1.56" diameter axles riding on a single bearng bearing that sometimes broke. Those axles bear all the weight and also hold the wheels on. The V6 axles are the same. With a full floater, NO weight is on the axles and they do not hold the wheels on either. I also read the many reports made about Toyota RV failures along with the various investigations and rendered opinions. I saw none that stated with any controlled testing that fake dually wheels were the only cause. A few "experts" made assumptions. Obviously, if it was JUST a "fake dually" issue with a dangerous offset - Toyota would not have spent the bucks on furnishing new dually full-floating axles.

[Maineah]

There was a later module Tacoma on the Tacoma users site a few weeks ago sitting on the side of the road with a broken axle the owner admitted to overloading it and to make matters worse he had done the same thing welded duel wheels do with wheel spacers. It broke exactly where the MH's do right at the flange where the axle meets the hub. With a single bearing it flexes there when it's overloaded and eventually fails the only thing holding it together is the radius at the hub..

[zero]

When Toyota was selling USA mini-trucks in the 70s-80s, I doubt they had a 5000-6000 lb. constant payload in mind. Not with the semi-floaters. People sometimes grossly overloaded their trucks but not for their entire useful lives. When a truck is sold specifically for constant heavy use - the design and ratings tend to be quite different. Usually built heavier and with more conservative ratings for weight and horsepower. Sell a passenger car or truck rated 300 horsepower and it is assumed that max power will rarely be used. If it was, many would likely fail before the warranty wore out. Sell a HD vehicle with a max power rating and it is apt to be used hard much more.

Every seen the many module homes being trucked down the highways on mulitple Dexter axles? Many of those axles are rated 5000-7000 lbs. each. They have bearings and axles MUCH smaller then you'd find if you bought a DOT rated equipment trailer with the same weight rating. They also odd-ball 14.5" non-DOT rated tires. Why? The Dexter axles and tires used to transport mobile homes are generally regarded as "one time use." Trailers sold to the public that are expected to be used for many years are built heavier. This has caused some highway headaches because many of those "one time" use axles wind up in home-made equipment trailers.

I suspect this same sort of thing came into play with Toyota RVs. The semi-floating rear axle has somewhere around a 3300-3600 lb. "safe long term" rating yet Toyota has claimed it's been tested at 5000 lbs. How long, I don't know. That all seems fine on a small truck with passenger car 14" tires. It's likely the tires would fail before the axle with a severe overload. But when they became 5000-6000 lb. RVs with truck tires and duals? Weak link was the axles themselves.

This same sort of thing is still going on with GM 6.2 and 6.5 diesels. They have a tendancy to suddently break crankshafts and main bearing webs. Many people have made guesses as to why including engineers from Detroit Diesel and GM. The cranks are cast-iron instead of forged steel which is unusual for a diesel engine. These engines were first created by Detroit Diesel as low power "economy" engines. A 379 cubic inch engine with equal power to a 305 cubic inch gas engine but with 30% better fuel mileage. But as years went on - they became something else with more power and turbos added. Then the US military adopted them and are still using them and it's a big mess. Many, many failures. A case of "mis-application" just as the Toyota RVs were with the small axles.

[Stevo]

I'm not trying to open a can of worms here but I just spoke to a guy yesterday with an 18' Toyota Sunrader factory 4X4 he bought brand new in 85. It has 250,000 miles on it with the 1/2 ton rear axle and he has never had any problems with the axle. He told me that to avoid breaking the axle he is very careful about keeping up with bearing maintenance and that his outside tires always have about 10 PSI less pressure than the inside tires. Interesting, eh?

[zero]

I'm not trying to open a can of worms here but I just spoke to a guy yesterday with an 18' Toyota Sunrader factory 4X4 he bought brand new in 85. It has 250,000 miles on it with the 1/2 ton rear axle and he has never had any problems with the axle. He told me that to avoid breaking the axle he is very careful about keeping up with bearing maintenance and that his outside tires always have about 10 PSI less pressure than the inside tires. Interesting, eh?

Many automotive failures are in part, due to negligence in some way. But . . . automotive design usually accounts for that percentage of negligence and mis-use and overbuilds to make up for it. Obviously - not with Toyota RVs. I've come across a few 21 foot Toyota RVs with the OEM 1/2 ton axles that are reported as being original. Personally, I have no interest in "vacationing" in a vehicle that is borderline-overloaded and beyond safe weight capacity.

[artoy]

I am new here and wanted to say a great many thanks to everyone's input on the rear axle forum thread. I just acquired my first dolphin (1982). At the point of sale the seller alerted me to the presence of loose driver side lug bolts. He torqued them I went forward with the purchase unbeknowst to the significance of loose bolts and problems with the 1/2 ton axle (Toyota recall). I must have fallen in love with the size and look of the vintage camper, window(s) and window layout, expected fuel economy, etc. I still like her but now Im stuck with the 1/2 ton, semi float 5 lug axle.

Last week Murphy's Law kicked in and a few of those driver "dullys" lug bolts became loose again due to what I now know to be enlarged lug stud holes (on the dully wheel itself) and sheared three studs off while driving! The plot thickened as I limped along with a noisy wheel being held on by just two lugs, made an abrupt turn into a roadside parking space, cutting off/hitting an oncoming cyclist who was in my blindspot. Yikes!! She's fine Thank God and escaped with some nicks and scrapes and minor bruising.

I later had the Dolphin towed to a shop (A and B recycling San Diego--ask for AJ). Mind you the exact cause of this hole enlargement is unknown and could be something as "innocent" as impromper torquing but we (me and the shop) suspect the overall weight issue visa vie the 1/2 ton semi float dully to be condusive. Getting the rig lifted I was surprised to learn that after over 100,000 miles the bearings are fine, no leaks, good play, some leaf spring drop and minor bushing wear around rear leaf springs. I got away with replacing the sheard lug assembly and removed both sets of dullys. I know I am supposed to due an axle swap and the shop has a 1-ton 6 lug dully axle and wheels available and will do the job for an estimated $1000-$1200. I am considering and in the interim thought to try and lighten the camper enough to get away with single 14" wheel and beefy D (1800 lbs load per side) tires per side. For now I am limping around with this single wheel set up on 5 year old D tires (another bright idea as the tires and probably too old).

While on the highway I am now noticing serious understeer as a result of removing the dullys. But the load on the axle is probably more centered around the single bearing per side per the forum posts and less likely to fail. I plan on contacting the NTSB or related to alert them to what I have experienced. Toyota is playing dumb with me and had the audacity to tell me that they never heard of the Dolphin. I am aware that the recall ended in 1995 or when National who built the Dolphin went bankrupt in 2007 I believe.

Edited September 23, 2014 by artoy

[Maineah]

With the fake duellies it just exasperates the problem. You really are better off with one e rated tire per side. The axles snap off right at the radius where the shaft meets the hub from flexing adding another wheel places even more stress at that point. The worst part is when the brake drum follows the hub because it still is bolted to it along with the wheel not a pretty sight. Toyota sold rolling chassis they did not make or were a part of any motor home the coach makers were the ones that over loaded the axles if you look at your MH you will see two ID plates one from Toyota the other from the coach maker the Toyota GVW rating was grossly exceeded by the coach makers and they knew it. It does not surprise me that your Toyota dealer never hear of a Dolphin they didn't make them.

[zero]

If anyone has put the '87 up DRW axle in a 1979-1983 Toyota RV please contact me. I'm still not sure how the later model rear end attaches to the older body style. Is fabrication required?

I put the so-called "1 ton" rear axle in my 1978 Chinook. The donor rear axle came from a 1987 dually box-truck. The OEM semi-floating 5 lug axle (like you have) is rated for around 1 1/2 tons max weight. The dually so-called "1 ton" full-floating axle with 6 X 7.25" lugs is rated for 2 1/2 tons. In itself the term "1 ton" axle is kind of useless.

Here are the changes I had to make to install that dually full-floater in my 1978 Toyota.

#1 - the axle tubes are different diameters. So U-bolts with a different curve are needed to be made or bought that clamp the axle-tube to the springs.

#2 - since the axle tubes have different diameters, the bottom brackets that the U-bolts attach to also need to changed.

#3 - the shock mounts are different. 1978 has both shocks mounted in front of the axle and the bottoms attach to the spring-u-bolt brackets. Later trucks have staggered-mount shocks. Toyota never made the front-mount brackets for the larger axle tubes so some fabrication is needed.

#4 - the frame rails and spring-packs are closer together on the older trucks. So a newer axle - like a 1987 - will need to have the spring perches cut off and rewelded closer together to mate with the springs and frame-rails on an older truck.

#5 - the rear stabilizer-bar from a later full-floater can be attached to the narrower-spaced older frame-rails if you make new brackets for the stabilizer-link-ends.

I've installed later full floaters into two older 70s Toyota trucks and have plenty of specs and photos if wanted.

[zero]

One other item I forgot to mention. The older trucks have small U-joints on the driveshaft and the old driveshaft flange will not bolt up to the the flange-hub on a newer full-floating dually axle. Also, you cannot take the flange-hub off the older semi-floater and install on the newer full-full floater because the spines on the pinion input are different. One fix is to get an aftermarket pinion flange for the duallly rear that comes with multiple bolt patterns. Another fix is to just take the Hotchkiss center-section (with the ring & pinion assembly) out of your old semi-floater and swap it into the dually full-floater. It is a bolt-in swap and works fine.

[Derek up North]

In itself the term "1 ton" axle is kind of useless.

I find it very useful because everyone knows what's being referred to. When you wrote: "I put the so-called "1 ton" rear axle in my 1978 Chinook." I knew exactly what you'd done.

Accurate, perhaps not.

[zero]

I find it very useful because everyone knows what's being referred to. When you wrote: "I put the so-called "1 ton" rear axle in my 1978 Chinook." I knew exactly what you'd done.

Accurate, perhaps not.

I see "1 ton" used, just in the context of Toyotas, that is not always a reference to the full-floating, 6 X 7.25" rear-axle assemblies. Thus my comments. Perhaps you always know exactly what is always being referred to. I need more context. That is especially true with the "mystery" 1 ton 5 lug axles sometimes brought into these conversations. If they exist, what are they? What is their actual max weight-bearing capacity? The full-floating Dyna/Toyota rear axle can bear 3 tons and live to tell about it. My 3/4 ton Dodge diesel truck has a rear-axle rated at 5 tons. Toyota sells pickups with "1 ton" payload capacity yet their rear-axles are semi-floaters and not much beefier then the 5 lug axles being discussed here. I suspect this is why "1 ton" Toyota rear axles show up for sale that are only light-duty semi-floaters. Seems fair, in a way, to call them that since they come from trucks rated to carry 1 ton of weight.

[YuupJeff]

My FIL owns a 1980 Toyota little chief. It runs the 4 cyl 20R engine and is the 4 speed manual. We are looking to do a rear end swap with another compatible 1-ton vehicle since this vehicle did not get the real axle recall fixed. Does anyone know what models we should look for that have the most compatible rear to replace it with?