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Were there different versions of Mack's plus-3 Cabs?


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I have always found the plus 3 cabs on the R and DM models to be more appealing than than the original flat back cabs pre 1973. However to me the back of some plus 3 cabs look different. For example the back of some R models don't look as curvy as some DM models. Where there different versions of the 'plus 3' cabs?

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1 hour ago, JoeH said:

For those of us who have never heard of them, what's a plus 3 cab?

Before 1973 the R and DM models had a 'flat' back cab. After that the back were extended about 3" to make the cabs more roomy, they called these 'plus 3' cabs. The flat cab was still available on the U models.

mack flat cab.jpg

mack plus 3 cab.jpg

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I believe the basic dimension of the +3 (CA 49) stayed the same but there has been some discussion that the body line crease next to the grab handle is present on same trucks and not on others.

Jim

It doesn't cost anything to pay attention.

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U and DM 600 series rear body panel is bulged and not a full +3 , uses pre 73 roof. That give the more rounded look. The +3 R series in flat as per Hollander Crash books.

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"OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK"  Thomas Edison

 “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’

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Well I  believe the plus as you blokes who call it was a Australian first thought of and produced down under deal

Due to a shortage of cabs from states Mack Australia made its own R model fiberglass cabs  for a while and these were the first to have the buldge in the back of the cabto allow for it to be double skinned

When the US saw this they set about making all R models the same 

This story has been told to me several times over the years and l believe it is even mentioned in the book about Leader trucks which were made by the same company  that owned Mack Australia at the time

 

Paul 

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I think the U model came with the flat backed cab as standard to preserve the 90 inch BBC but could be specd. with a plus 3 cab if BBC wasn't critical.

I think the body line crease behind the grab handle appeared in the late 70's but wasn't present on the earlier plus 3 cabs. Apart from that I can't see any difference in the curvature of the plus 3 back panel.

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3 hours ago, Rob said:

If I remember correctly the "U" series never got the +3 cab. The "flat back" cabs always had the small grab handles like the B series used, (at least here). This is my 1972 parts R-685, and a B series cab:

image.jpeg.ae71aebfba4ec61e4f7b9d29c47a0b59.jpeg

I've got a U single axle dump with the long handles. I forget if it's a + cab or not.

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We purchased 4 or 5 of these in the mid 1980's used.  They were late 70's/early 80's models and they had the long grab handle. These were great little city tractors. Power steering, A/C, with a pup you could almost do a u-turn on a city street with them.

 

U model Macks - Copy.jpg

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If I am not mistaken some of the early U models had the bump for the short handle but used a U shaped long handle that started from the top two bolt holes, then came out and down a ways then doubled back up to connect to the bottom two holes. I believe I had one of these handles out in my shop, I will have look to see if it is still there.     terry:MackLogo:

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Mine has the same grab handle as the newest RD's, I pulled the pass side off the U to stick on my 2001 RD tractor. Fit like a glove. I've got the stomach bug, so I'm not going out today to see if it's a flatback or +3 cab.

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3 hours ago, Swishy said:

So wot twaz the deal with the concave cab

so much trouble to save a cupla inches

cya

Same reason Kenworth  do It Today Swish.. To stay within the overall length Rules..

"Be who you are and say what you feel...
Because those that matter...
don't mind...
And those that mind....
don't matter." -

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16 hours ago, Swishy said:

So wot twaz the deal with the concave cab

so much trouble to save a cupla inches

DSC00948.jpg

 

cya

I think it was a mistake, and they welded it together inside out.   Atleast I'd like to cut mine out, flip it around, and put it back together.  

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The DM and U flatback cabs are both a Mack CA 361 (w rider seat) before the +3 cab came along.

After the +3, the DM cab was a CA 491 (w rider seat) or CA 492 (without rider seat).

The U model remained with a 36 series flatback cab but the CA 491 cab (+3) was available in 1981 until the end of the U model production.  I believe the CA 363 designation used reflects the change to a plastic dash with a flatback.

The flatback R models are a CA 36 and the +3 R model cab is a CA 49.  The RW Superliner cab is a CA 494.

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Jim

It doesn't cost anything to pay attention.

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