Home » Public Forums » GMCnet » Differences between a 73/74 and 76+ models
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| Re: [GMCnet] Differences between a 73/74 and 76+ models [message #170184 is a reply to message #170181] |
Sat, 19 May 2012 13:20   |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Bill,
There were improvements made to the coaches over time. Some are significant, some don’t matter if the coach was upfitted by a third party, such as Coachman. I’m hardly a GMC historian, but I believe the following to be true:
’73’s had a smaller diameter shaft where the rear bogies attach and a different door lock.
Somewhere around late ’74, ’75 or ’76 saw the introduction of improved seating by Flexsteel, Electro-level air bag controls (and the compressor moved inside the coach), and Type II dash air conditioning. Window latches were changed, and fresh water plumbing went from copper tubing to PEX. Radial tires were fitted to the coaches. The sub-flooring was improved with thicker plywood and metal sheathing. The steering wheel was changed from 2 spoke to 3 spoke.
In mid ’77 GM finally made the dash air work and changed the engine to a 403, instead of the 455. Changed to Electro-Level II using two compressors. The way the bunk-beds attach to the roof structure was changed so that the clasp was on the end of the seat belt and the buckle was in the roof.
I don’t know of any updates to the Onan over time, or to the brakes, transmission, roof air, or final drive. I would prefer a 1978 coach, all things being equal, to any other. Sadly, in California if your coach is ’76 or newer you are subject to smog-checks, and therefore can not improve the drivetrain with electronic fuel injection and spark control.
I know I’ve missed a ton of things, and probably flubbed a few, but I’m looking forward to this conversation. To date nobody has improved the style of the coach, nor surpassed it!
Larry Davick
The Mystery Machine
1976(ish) Palm Beach
Fremont, CA
On May 19, 2012, at 10:24 AM, Bill Walton wrote:
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> This has likely been discussed before but I couldn't find anything on a search. What would be the main considerations when looking at a 73/74 model versus a later model 77/78. In searching I did find reference to the older models attached the frame to the body in a different way and not as good as in the newer models, also the floor beams were thicker in the later models which allowed for more insulation but a little less interior height. There was also something about the rear axle's and how they were attached or there diameter versus the later models. Are there any other major design differences over the 4 or 5 years of models that would make a later model year far superior to the older year? Is there a spreadsheet or chart that lists all the differences in the model year designs?
>
> Thanks
> Bill
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Differences between a 73/74 and 76+ models [message #170192 is a reply to message #170181] |
Sat, 19 May 2012 16:08 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| bwalton wrote on Sat, 19 May 2012 11:24 |
This has likely been discussed before but I couldn't find anything on a search. What would be the main considerations when looking at a 73/74 model versus a later model 77/78. In searching I did find reference to the older models attached the frame to the body in a different way and not as good as in the newer models, also the floor beams were thicker in the later models which allowed for more insulation but a little less interior height. There was also something about the rear axle's and how they were attached or there diameter versus the later models. Are there any other major design differences over the 4 or 5 years of models that would make a later model year far superior to the older year? Is there a spreadsheet or chart that lists all the differences in the model year designs?
Thanks
Bill
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Bill, if the condition of the coach is equal, go for as late as possible. The 78's have many improvements to the suspension, cooling, engine and AC. However, overall condition of the coach no matter what year it is is still a major factor. I would stay away from the early 73's no matter what.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Differences between a 73/74 and 76+ models [message #170222 is a reply to message #170181] |
Sat, 19 May 2012 20:16 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Air dams were added like 76??or 77?? to better funnel air to the radiator. ELI controls moved from front to side for 76 to 77. I have an early (Sept) 77 so it still has a 455 but not the OE engine block anyway so you could buy a late 77 or 78 and still swap to a 455 if need be. Later dash air is the biggest improvement for me.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Differences between a 73/74 and 76+ models [message #170248 is a reply to message #170208] |
Sat, 19 May 2012 22:58 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| ggroth wrote on Sat, 19 May 2012 17:37 |
Bob, do you have a TZE number for "early?"
I'm not looking at any problems, but just wondering.
Thanks, geo
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I don't but I'm sure others will pipe up soon.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Differences between a 73/74 and 76+ models [message #170255 is a reply to message #170181] |
Sun, 20 May 2012 01:45 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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| bwalton wrote on Sat, 19 May 2012 10:24 |
This has likely been discussed before but I couldn't find anything on a search. What would be the main considerations when looking at a 73/74 model versus a later...
Thanks
Bill
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In California, '76 and newer must be smogged every two years.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Differences between a 73/74 and 76+ models [message #170261 is a reply to message #170255] |
Sun, 20 May 2012 06:26 |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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In Colorado, '76 and newer are also required for smog testing
On Sun, May 20, 2012 at 12:45 AM, George Beckman <gbeckman@pggp.com> wrote:
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> bwalton wrote on Sat, 19 May 2012 10:24
> > This has likely been discussed before but I couldn't find anything on a
> search. What would be the main considerations when looking at a 73/74 model
> versus a later...
> >
> > Thanks
> > Bill
>
> In California, '76 and newer must be smogged every two years.
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Bruce Hart
1976 Palm Beach
Milliken, Co
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: [GMCnet] Differences between a 73/74 and 76+ models [message #170285 is a reply to message #170261] |
Sun, 20 May 2012 10:32 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Same here in the Portland Oregon Metro area, but if you have "antique" (aka "SP" Special Purpose) plates you do not have to smog it all. To get SP plates the vehicle needs to be over 25 years old. (It does have some restrictions.) They also do not expire.
| Bruce Hart wrote on Sun, 20 May 2012 04:26 |
In Colorado, '76 and newer are also required for smog testing
>... What would be the main considerations when looking at a 73/74 model
> versus a later...
> >
>
> In California, '76 and newer must be smogged every two years.
> --
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Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Differences between a 73/74 and 76+ models [message #170325 is a reply to message #170181] |
Sun, 20 May 2012 17:55 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I have not driven a 403, but my 455 with stock gears at 3.07 seems fine. At highway cruse I like to do 65 so I wouldn't want more than like a 3.42, though on paper I'm below the torque curve. Others would say Higher numbers would be better. I'd love a 3.55 in the city and stop and go traffic so the torque converter wasn't doing what the gears should, but with 3 forward gears, so it is. From what I know the 403 is fine with a 3.55 or better and that makes sense to me. If it's spark and carb are setup right I don't think there is much difference or disadvantage. Maybe pulling a toad on a grade it would matter but....
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Differences between a 73/74 and 76+ models [message #170326 is a reply to message #170181] |
Sun, 20 May 2012 17:58 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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And I bet the mileage is right about the same. The work being done is the road load of moving 11K#, and 52 cubes is not that much, though torque is mechanically less.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Differences between a 73/74 and 76+ models [message #170333 is a reply to message #170299] |
Sun, 20 May 2012 19:06 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| bwalton wrote on Sun, 20 May 2012 10:43 |
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-there seems to be a feeling that the 455 was far superior to the 403....why? is the 403 just way under powering the coach or was the 455 just a better engine........
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I have both. The 455 seems to have a little better pulling power (ie: torque) and the 403 gets slightly better mileage. There are reasons for this dealing with the 455's SMALLER bore and much LONGER stroke giving it a torque curve that is lower in RPM than the 403. The 403 is a smaller package not requiring the "special" extra low rise intake to fit under the hatch. I have been told the 403 can have the same effective pulling power by installing a slightly lower (higher number) final drive. Both engines should benefit from a change in ratio... the 403 a bit more than the 455. Even without a ratio change, if you live and drive in the flatter areas of the country, you'll most likely not notice a performance difference between the engines.
Pretty much, the condition of the engine is more important than the size.
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... given that all things are equal; mileage,options,condition etc how much less would a 73 be worth by virtue of the fact its 5 years older 50% 60% ...
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Like engines, condition is more important when setting value than what year the coach is.
The original equipment is the biggest differences and if the coach has been re-done, what was there has been changed... putting a money value on the value of the changes for each year would need to based on what _YOU_ think of the changes... IE: The early coaches had "wood and foam" based furniture, the later came with Flexsteel automotive type seating. I find the later seats are better to sit on, the but early foam makes a much better sleeping surface. So the question is: "How is it going to be used the most?"
If I HAD to put a money value on it, I would say about $1000 differences between the early and when the 1975's got all the major changes for that year... better rear boogies, Imron paint, better cabinets, flexsteel seating, redesigned front pedestals and updated (Herr??) windows. (This point is somewhere in the middle of the 1975 model year.) I might give an additional $500 to 600 for a 77 over a 76 due to the improved dash air and few small changes. Some would REDUCE the value slightly for a mid 77 on... due to having a 403. (I would not.)
I'll see if I have time to compile a list of changes that I know about.... this reply is getting too long.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Differences between a 73/74 and 76+ models [message #170345 is a reply to message #170181] |
Sun, 20 May 2012 20:35 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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It is a good exercise to identify the production differences and as the owner of an early 73 I like to know the timeline of the changes, but it seems to me you would be better served to assess the merits of the specific coaches you are considering purchasing. So many have had various alterations/modifications that the original configuration may be unimportant. It's not like any of these are recent production.
For some, finding a working layout is first on the list. Rear bath, twin bed, etc.
Most importantly, try to determine what it will cost you to make the coach work for you. No matter what you pay for one, expect to spend a few $K for fixes and changes and unexpected issues.
BTW, in addition to the items others have mentioned, the early coaches had a desirable adjustable steering link, and an off position for the ac controls.
Dennis
| bwalton wrote on Sat, 19 May 2012 12:24 |
This has likely been discussed before but I couldn't find anything on a search. What would be the main considerations when looking at a 73/74 model versus a later model 77/78. In searching I did find reference to the older models attached the frame to the body in a different way and not as good as in the newer models, also the floor beams were thicker in the later models which allowed for more insulation but a little less interior height. There was also something about the rear axle's and how they were attached or there diameter versus the later models. Are there any other major design differences over the 4 or 5 years of models that would make a later model year far superior to the older year? Is there a spreadsheet or chart that lists all the differences in the model year designs?
Thanks
Bill
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Differences between a 73/74 and 76+ models [message #170352 is a reply to message #170192] |
Sun, 20 May 2012 22:06 |
Adrien G.
Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624
Karma: 1
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Senior Member |
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Bob & the rest on the forum,
I read this thread and so far no one has mention about the difference in floor structure between '73-74 and '75 and later.
I think that the alum floor joist structure is bound to add some rigidity to the walls since the frame in inboard of the walls, along with the floor insulation and alum cover.
Non of which the early model have. And if GM didn't find it necessary, I'm sure they wouldn't have added the extra cost.
JMO
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
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| Re: Differences between a 73/74 and 76+ models [message #170356 is a reply to message #170299] |
Sun, 20 May 2012 22:21 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""-there seems to be a feeling that the 455 was far superior to the 403....why? is the 403 just way under powering the coach or was the 455 just a better engine........
""
I think you will find just the opposite
Bob de Kruyff
78 Eleganza
Chandler, AZ
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