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

[JoeH]

So to throw everything off, here's a picture of a 1976 U685T flatback cab with long handles. Has the tan plastic interior that was used up to the end of the R series.

 

I think it was indicated that the flatback was pre 1973.

Just noted that Mr Hancock indicated the U model stuck with the flatback cab. Where would I look for a cab designation?

[Jamaican Bulldog]

On 3/10/2019 at 9:24 PM, 41chevy said:

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.

41 chevy. That is an excellent explanation!  A close look at these pics illustrates that especially looking where the back of the cab meets the roof on both. The DM tapers inward towards the roof which creates the bulge look.

[Whiskymack]

I still think there is no difference and that all the plus 3 back panels were the same excepting the addition of the vertical body crease some time in the late 70's.

The top corners of the roof panel were substantially radiused so the bulge appears more prominent when the cab is viewed from the front corner but less when the cab is viewed side on. Follow this link to see this.

https://www.purplewave.com/auction/120228/item/A6751

I'd also argue that, after the plus 3 cab was introduced, the long grab handle was standard on all the R,U,DM cabs including the flat back cab which was retained as standard on the U. It looks like the panel was modified to eliminate the mounting bump for the old short handle.

The U could be ordered with a plus 3 cab. There was one for sale on here a few years ago.

[j hancock]

3 hours ago, Whiskymack said:

The U could be ordered with a plus 3 cab. There was one for sale on here a few years ago.

Whiskymack has nailed it. 

After doing some research, the CA 491 (+3 cab) was indeed an available option on the U model from 1981 until the end of its production.

[Jamaican Bulldog]

On 3/12/2019 at 9:35 AM, j hancock said:

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.

Btw are DM and U model cabs interchangeable despite having different chassis? 

[JoeH]

23 hours ago, Jamaican Bulldog said:

Btw are DM and U model cabs interchangeable despite having different chassis? 

If you cross reference the U and DM cab numbers you will get a Yes. "Rider seat" is passenger seat. 

[41chevy]

On 3/13/2019 at 2:13 PM, j hancock said:

Whiskymack has nailed it. 

After doing some research, the CA 491 (+3 cab) was indeed an available option on the U model from 1981 until the end of its production.

But Wait!!  There's more! DM was available as plus 3 from 1974 on but not the U until 81.

[j hancock]

8 hours ago, 41chevy said:

But Wait!!  There's more! DM was available as plus 3 from 1974 on but not the U until 81.

Yup, who would have thunk it.  All this for 3 easy payments of $19.99