2009 Powerglide Chassis Road Test and Review

Introduction

Tiffin Motorhomes uses many chassis in their motorhomes, including Ford, Workhorse, Freightliner, and Spartan. Recently they've begun to make their own proprietary chassis, which is called the Powerglide. There are very few RV manufacturers who have created custom chassis for their motorhomes. It is quite an endeavor so most prefer to rely on a dedicated chassis supplier so that they can concentrate on the "box" end of things. However, those who have created their own proprietary chassis have reaped a few benefits in the process. Manufacturers such as Country Coach with their Dynamax chassis and Alpine Coach with their Peak chassis have a great number of RV owners who really enjoy their chassis. Having a proprietary chassis means that you can custom design each chassis for any given floor plan. It gives the coach builder the ability to make upgrades and improvements to it whereas they are not apt to get that if they are buying their chassis from a chassis vendor. It also eliminates the "not my fault" syndrome where owners can get bounced around with warranty issues. There are a number of times where it's difficult to determine just who is responsible for a warranty issue. When the builder of the chassis is the same as the builder of the coach there's no more finger pointing. It all resolves to the same company. Given Tiffin's legendary reputation for standing behind everything they make, this puts the owner of a Powerglide chassis in a great position.

However, this only is a benefit if the chassis is engineered and manufactured with sound engineering and quality components. These were questions I had going in. The Powerglide has been around about a year now and owner reports tend to indicate that Tiffin has no bugs in this chassis and it's a solid design. I recently had the opportunity to inspect and road test an Allegro Bus with the Powerglide Chassis at King's Campers in Wausau, WI. They had a 36' Allegro Bus and a 43' Allegro Bus but I choose to test a 40' Allegro Bus instead. I felt that the 36' Bus would be a sporty handling RV and not representative of what the typical RVer would find on a 40' coach. Likewise, the larger tag axle coaches are so rock solid that it'd be hard to tell the difference, so I chose the 40QRP, where I felt the most difference could be seen and would apply to the vast majority of RVers. I thoroughly inspected the unit, took some pictures, and gave it a good road test. I'm posting this so that the TiffinRVNetwork members can see some pictures and descriptions of this great coach.

Note that I have also uploaded larger 1024x768 (XGA) images in addition to the smaller ones shown in this review. If you want to view a larger picture simply click on the image in the review and a new window with a full screen image will appear.

If you would like to print this review it probably won't work that well. The pictures and text on the far right will probably get clipped. If you want to print this review, Click Here for a Print Ready Version.

Feel free to download or save any of this text or images if you want. If you repost any or part of it to any other website just be sure you don't change any of my wording and please mention where it came from.

Mark Quasius - "Cruzer"

Chassis Overview

At the present time the Powerglide is only available on the Allegro Bus. It's been around in it's single axle form for about a year now for the 40' coaches but recently has been made available in a tag axle version for the 42-43' coaches. Other than the implementation of the tag axle the basic design is unchanged. Eventually Tiffin Motorhomes plans to expand the Powerglide offering to other models but as of right now it's limited to the Allegro Bus. Interestingly enough, if you want to order the shorter 36QSP Allegro Bus it is only available on the Powerglide. There are no Freightliner or Spartan offerings for that model. When Tiffin first introduced the Powerglide they expected it to be a slow start up but it actually has taken off much better than expected and the orders for Powerglide chassis have been better than predicted.

The Powerglide is a side radiator rear engine diesel pusher chassis that uses the 425 HP Cummins ISL engine. In that way it's very similar to the offerings by Freightliner and Spartan. However, it does have a few unique features that separate it from the other brands. Here's a quick summary of them:

• Huck bolted ladder type frame - A stronger method of joining the frame members compared to rivets.
   
• Grade 8 dichromate plated fasteners - Dichromate offers greater resistance to rust and corrosion while grade 8 is a stronger fastener than grade 5. Exclusive use of grade 8 fasteners throughout eliminates the possibility of accidentally switching a nut with a lower grade.
   
• Direct driven radiator with 2 speed fan clutch - Rather than use hydraulic pumps to drive a hydraulic fan motor the belt driven design allow a fan clutch to disconnect that load from the engine, theoretically improving fuel economy. It also eliminates any hot hydraulic fluid, which can start a fire should a line burst and removes that heat from the engine compartment.
   
• Improved weight distribution - Today's single axle coaches can get heavy on the rear axle and light on the front. The 40/60 split of the Powerglide shifts more weight to the front axle for more stability and greater rear axle capacity.
   
• Multiplexed electrical system - Eliminates many of the wiring harness connections common to a non-multiplexed RV. It also ties all components together with communication over the J1939 data buss for better control of all electrical devices.

There's lots more than this so if you want to check out the tech sheet on it please access www.rvtechlibrary.com/chassis/powerglide.pdf in the RV Tech Library.

Just a note on the rear axle. Tiffin uses a heavier rear axle with a 22,000 lb rating rather than the typical 20,000 rear axle. While having a larger rear axle is fine in that it provides greater durability, care should be taken to keep things legal. The Federal Bridge Law limits any single axle to a maximum of 20,000 lbs. If you load your axle more than it is technically illegal. Now, RVs really don't generally get stopped and weighed by the authorities but it can happen. Monaco used 23K rear axles for a while on their heavier coaches prior to going to tag axles. A large number of Monaco owners were refused entry to the Ohio Turnpike because of this. In order to enter the Ohio Turnpike you have to drive over a pass-over scale imbedded in the pavement that checks your axle weights so that they can determine how much to charge for a large vehicle. If you are over 20K they will refuse entry. So, that is something to keep in mind if you decide you really need to run 22K on the rear axle. Most motorhomes come with a 20K rear axle so if you keep your rear axle weights to 20K there's nothing wrong with having a beefier 22K axle under your coach. Just don't use it to calculate how much carrying capacity you have unless you are driving somewhere that the Federal Bridge Law doesn't affect you.

Okay, following are some views of the various components that may be of interest. I mean a chassis isn't the most picturesque thing around but some of these points are worth a photo and some mention.

Engine Compartment

With the engine access hatches open it's easy to see one of the features of the Powerglide. The engine is mounted lower. The lower engine location lowers the center of gravity which should assist a bit in helping to control lean. It also provides extra clearance above which gives the coach designer the ability to lower the hump in the bedroom. This will undoubtedly happen in the future but as of now the hump is still there because the same "box" gets dropped on either Freightliner, Spartan, or Powerglide chassis. The ease of access is similar to Spartan in that the chassis batteries are located in the rear cap and the filters, dipsticks, and hydraulics are easily accessible. Like Spartan, a steel coolant surge tank is utilized to counter the cracked plastics tanks that Freightliner chassis owners experience. Note that the hydraulic reservoir shown is the same as Spartan although Tiffin uses a mechanical fan on the Powerglide, unlike Spartan. However, the power steering system still uses that same hydraulic system so the hydraulic reservoir is still needed.

This closer view, taken from the left, shows the fuel filters as well as the "radiator cap" on the coolant surge tank. Both the primary and secondary fuel filters are easily accessible from the rear engine bay doors. The secondary fuel filter is supplied from Cummins and attached to the engine. That's why every secondary fuel filter that comes off the line has Cummins red engine paint on it because they slop paint on it when they paint the engine. After you change the filter it looks much better. A manual disconnect switch for the chassis batteries can be seen at the lower right corner of this image.

This shot, taken from the right, better illustrates the dipstick locations and hydraulic tank. Also visible is a sight glass on the coolant surge tank that shows you the exact level of coolant in the tank.

Cooling

The cooling package consists of a stacked array with the charge air cooler stacked directly above, rather than behind, the radiator. The transmission cooler is a oil-to-water type unit inserted into the radiator. Because there is no hydraulic driven fan there is no need for a hydraulic oil cooler. The cooling package is certified by Cummins. The fan itself is fed via a gearbox that is driven by belts from the engine. A two speed electric clutch allows the fan to engage as needed. I did notice that the fan is slightly louder than my hydraulic fan on my Spartan but that is only noticeable when you are standing outside by the rear of the coach and not when driving. Either way, it's not objectionable.

Ancillary Compartments

The HWH hydraulic leveling system was located in a narrow compartment near the rear of the coach. The pump unit and reservoir are located just behind the electronics control module. This compartment is shallow due to the fact that the engine is behind it.

Near the rear of the coach is another compartment. This compartment houses the automatic transfer switch that switches between shore power and the generator set. It also provides a handy location for draining the air tanks. The red and green hoses lead from the front and rear air tanks. Each petcock allows the owner to drain the air from these tanks (it spits out the backside so there's no mess) without having to reach into the front fender well with an awning hook. This design makes it much easier and safer to drain the air tanks. Being this easy means it might actually get done more often too. Directly beneath the two air drain valves is a second auxiliary air connector that can be used to air up your tires, run pneumatic power tools, etc.

Instrumentation and Electrics

The Powerglide is unique to Tiffin Motorhomes so every time you see their name on the speedometer you'll know what chassis this is. The instrument panel utilizes white faced gauges that are easy to see. A cluster of 3 gauges includes a speedometer with integral LCD display, a tachometer with integral fuel gauge and voltmeter, and a cluster gauge with front air pressure, rear air pressure, engine oil pressure, and engine coolant temperature. The gauges are not wired in the typical analog fashion, but instead uses the Vansco multiplexed system's J1939 data buss to receive communication from the system. This digital interface reduces the connections required and improves reliability. One interesting characteristic of this system is that you can't jump in and immediately turn the ignition key to the start position. If you do, nothing will happen. Instead, you turn the key to the "on" position and wait about 5 seconds for the system to "boot up". Then you can turn the key to the start position.

The driver side front most compartment typically holds all of the fuse blocks and relays common to an analog system. The Vansco multiplexed system greatly reduces this wiring clutter. The two larger modules at the bottom are diagnostic interfaces. The LEDs will indicate the exact location of any electrical failure in the system and will greatly minimize diagnostic time and improve accuracy. A laptop computer can be used to interface with this system to perform any diagnostic procedures and/or record parameters.

The curbside rearmost bay houses the various relays and solenoids, such as the charge solenoid, slideout interlock solenoid, battery disconnect solenoid, etc. It also provides additional fuse protection for the trailer lighting circuits.

Road Test and Summary

Overall I was very impressed by the fit and finish of the chassis. Tiffin has spent a lot of time sweating the details on this chassis and the results are obvious. It excels in three areas - ease of service, quality of construction, and design and engineering. It's a very well built unit that has a lot of thought put into it. That, plus the backing of the Tiffin organization makes it a great choice for any prospective RV owner. But the proof is in the driving so that was the next step.

On our test drive I was able to toss the coach through some tight S bend streets near the dealership as well as drive the freeways. These were all roads I'd driven other coaches on so it was a good sample. I didn't want to just point it down the interstate and say it drove good.

I found that the handling was very similar to Spartan. The steering was nice and crisp and when you moved the wheel the coach responded immediately. There was no lag or mush involved. I did notice that the steering took a bit of effort to return to center after a hard turn. Both my Freightliner and Spartan chassis tended to snap back by themselves and return to center without as much guidance. With the Powerglide I found I had to direct it back a bit or else it stayed pointed where it was turned. Now, the steering wasn't heavy by any means and small course corrections returned well. But on a hard turn you had to bring it back more than usual rather than let it come to you.

Braking was excellent. The front disc brakes and rear drums hauled it down in good order and modulation was excellent.

I did find that the front end stayed in place a bit better. That's undoubtedly due to the greater weight distribution that places more weight on the front axle. It seemed that winds and bow wakes had a bit less effect on the rear of the coach compared to other single axle chassis. While not as solid as a tag axle chassis, it definitely is an improvement.

Overall, I found it to be a nice handling coach. Not a major improvement over others, but this chassis has a number of things that add up. There is no one outstanding feature that'll knock your socks off but there are a lot of small advantages. When you add them all together it can make for a compelling reason to buy the Powerglide.