Author Topic: GMC RTS II, type T70-604 question  (Read 6600 times)

Offline CivilEngineer

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GMC RTS II, type T70-604 question
« on: November 20, 2006, 01:43:33 PM »
I am an engineer working for a company which is redesigning a ramp to accommodate a bus.  The specified bus is a 1980 GMC RTS II coach, type T70-604.  I found some information online which states that the bus length is 35' and wheelbase is 239".  But the information I really need is:  where are the wheels positioned between the front and back of the bus; i.e. how much overhang on the front and back?  I need this information to accurately design the ramp and can't seem to find it anywhere online.  Does anyone have access to one of these buses for a measurement or know of where I could find this information?

Also, I measured several buses to determine an approximate height of the bottom above the ground, and found quite a variance.  I'm assuming most buses have an air suspension so height above the ground will vary depending on the loading inside the bus.  Can anyone confirm that this is correct?


Offline Chris 85 RTS

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Re: GMC RTS II, type T70-604 question
« Reply #1 on: November 20, 2006, 03:06:00 PM »
First off you need to join the best site on the web for RTS information:

Secondly, the RTS is comprised of 5' sections.  The RTS was manufactured with a wheel chair ramp already built into the rear door section.  It occupies the entire section.  I doubt there is enough room in the front section for much of a wheel chair lift, although I understand the later model RTS's built by TMC did have a front lift.  The module stackup would look like this from rear to front on a 35' RTS.

Engine - Rear Wheels - Rear Door - Air Tanks - Fuel Tank - Front Wheels - Front

The wheels are centered in each section.   The 5' dimension of the front section includes the front bumper, which likely sticks out a foot, and then another foot to the door opening, which I think is about 24" or so.  I can get much more accurate measurements if you like.  Here is a link to the framing of the unibody chassis:

Good luck.
1985 GMC RTS II 40x96 6V92TA MUI V731 IFS


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Re: GMC RTS II, type T70-604 question
« Reply #2 on: November 20, 2006, 03:11:52 PM »
I suspect the OP is building a ramp to drive the bus on which is why he needs the wheelbase, overhang, and so on to get the angle right on the ramp.

Brian Elfert

Offline Hartley

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Re: GMC RTS II, type T70-604 question
« Reply #3 on: November 20, 2006, 03:50:31 PM »
Hmmm.. Ramp?

If you are talking about a drive-on ramp your best method would be to ask one of your local
heavy equipment movers that has a Landoll ( rollback ) trailer to help you figure it out with the
bus that you are designing for. Of course you need the bus too...

Generally an RTS has about a max of 14 Inches ground clearance with the air up.

The front wheels and axle are approximately 7 feet back from the front bumper. Depending on the bumper
a standard Class C wrecker needs to extend it's lift boom 9 feet for the wheel lift.

There is approximately 6 1/2 feet to the front section. ( 5 feet for the shell ) and another 1 1/2 feet for the bumper.
The front axle is 1/2 way centered in the second 5-foot modular section.

The Engine is located in the rear-most section which is 5 feet, The rear axle is located in the next forward 5 foot section
and centered in the module. The rear bumper is also about 1 1/2 feet.

If you bottom out an RTS or any bus for that matter you can cause severe damage to the structure and mechanical systems. If you bang the front you can twist the body. If you bang the rear you can break the engine cradle loose, crush the radiator and exhaust system and bend up a lot of expensive stainless steel. The bad part is that you can't really see the damage at first. That 6,000 lb engine cradle is fragile since it is held in with only 4-bolts. Two hold it up (totally) at the rear and two hold in in place on each side at the rear bulkhead on machined cast cradle mounts.

Many parking lot designers did not design the slopes of the entrances to accomodate the overhang on Transit buses and an RTS will bottom out harshly when entering ot leaving parking lots and side streets that have low spots or angles over about 15 degrees.

Most over the road buses also will have problems with incorrect ramp angles as they also have axles located far inboard from the bumpers and structural areas under the front and back.

School buses generally are built with excessive ground clearance just for these reasons. The long tail ends on most school buses have in excess of 24 inches of clearance and can still be bottomed out by a badly angled ramp. Some have over 12 feet hanging behind the center of the rear axle.

If you are a civil engineer, You already should have resources to look up the DOT standards for Roadway design.

Good Luck.....
Never take a knife to a gunfight!

Offline tekebird

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Re: GMC RTS II, type T70-604 question
« Reply #4 on: November 20, 2006, 05:39:37 PM »
1.  I forget what the numbers mean in the model type.

     Are you sure it is a 35 foot version?

     It was also produced in a 30 and 40 foot versions as well

2. What you are looking for ar approact and departure angles.

    This will be dependant on if they are using the OEM size wheel/tire

3. Where are you located?

4. feel free to email me at

Offline RJ

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Re: GMC RTS II, type T70-604 question
« Reply #5 on: November 20, 2006, 09:21:26 PM »
Doug -

T70604 translates as follows:

T  = Transit
7  = 7 five-foot modules = 35 feet
06 = 96" wide
04 = Series 04

Kim -

According to my RTS brochure, here's the dimensional data.  Unfortunately, there's no departure angles listed.

Sorry about the poor resolution.  If you need better, send me an email and I'll forward on to you a better copy.

FWIW & HTH. . .


« Last Edit: November 21, 2006, 08:55:30 AM by Russ »
RJ Long
PD4106-2784: Donated to the Pacific Bus Museum
S14947: 1980 MC-5C Shell 6V92/HT-740 - Sold
S13406: 1978 MC-5C Angola Coach - Swapped for Vantaré
M1001907: 1992 Prevost XL Vantaré Conversion 8V92T/HT-755 (DDEC/ATEC)
Cheney WA (when home)

Offline Runcutter

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Re: GMC RTS II, type T70-604 question
« Reply #6 on: November 21, 2006, 08:52:37 AM »
Interestingly, the maintenance manual doesn't give approach/departure angles either, so I went to my copy of the specs - from buying a fleet of 80604's.  The White Book (Baseline Advanced Design Transit Coach Specifications, November, 1978) was the baseline specification that the RTS and Flxible 870/Metro (and later the Neoplay) had to meet - properties inserted their special requirements (paint, seats, block heaters, signs, and the like).

The White Book (Page II-9) calls for Ramp Clearance - Approach angle no less than 10 degrees, breakover angle no less than 10 degrees, departure angle no less than 9 degrees.  Ground clearance no less than 10 inches, except within the axle zone and wheel area.  Axle Clearance no less than 6 inches.

Since I also read (after re-reading) the original posting as having to do with a drive-on ramp, it's probably also worthwhile to note two things.  The bidders' vehicles could not fall below these specs, or they'd be non-responsive - so what are the real RTS numbers?  Second, I would anticipate that these specs are for a fully aired-up, roadworthy bus - since there's no reason to care about approach/breakover (middle of the bus going over humps)/departure angles if the bus is parked in the yard.


Please forgive if this is a second post - after completing it the first time, it disappeared into the great unknown.

Arthur Gaudet   Carollton, TX
Arthur Gaudet    Carrollton (Dallas area) Texas 
Former owner of a 1968 PD-4107

Working in the bus industry provides us a great opportunity - to be of service to others

Offline pvcces

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Re: GMC RTS II, type T70-604 question
« Reply #7 on: November 22, 2006, 06:44:36 PM »
Kim, it seemed to me that you overlooked the air suspension that is standard on these coaches. Load will have no effect on the clearance unless the coach is overloaded to the point that the air pressure in the system will not be able to inflate the bags to a height that will shut off the leveling valves.

For a one time or special purpose, there might be a few inches of clearance available by resetting the leveling valves. Some converters have rigged up leveling systems that take advantange of the air suspension to level the coach in a campground. Such a system can also temporarily raise the height 3 inches or so to clear an obstacle.

I recall that the Subaru Outback is equipped with a means of raising the body for extra clearance.

Good luck on your research.

Tom Caffrey
Ketchikan, Alaska
Tom Caffrey PD4106-2576
Ketchikan, Alaska

Offline RTS/Daytona

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Re: GMC RTS II, type T70-604 question
« Reply #8 on: November 23, 2006, 04:05:43 AM »

I,ve added my own design ---"Campsite Airbag Override"  - 3 point system to my RTS - I can raise / lower any "CORNER" of my 35' RTS  bus approx 10-12 inches - (the RTS bus 7.5 foot axel setbacks amplifies any airbag height change at the corners - simple fulcrum action)

Pete RTS/Daytona 
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