Frame Commonality

[doubleclutchinweasel]

Greetings, all!

I am in the planning stages of building an antique Mack R-model truck. I have already done much research, and have met several folks in the business (some very helpful, others...not so much!).

I had planned to build what would essentially be an R611T, with the ENDT-673 Thermodyne and an 18-speed Quadruplex. This would essentially duplicate (on a somewhat lighter scale) the truck I drove (too many) years ago.

But, it looks like it will be easier to build an R685T, as there are more ENDT-675 Maxidyne engines and Maxitorque transmissions available. Oh, well!

I have recently seen, in person, an "R" truck on a U685 chassis and another on an F685 chassis. This, along with some comments from one of the more helpful gents at the Mack museum, makes me think that the basic chassis of all 3 of these models are the same, with crossmembers and other components positioned as-needed for the various models.

Does anyone have direct, personal experience with swapping cabs & frames between these F, U, and R model trucks?

Thanks!

[umodelnut]

I am going to have experience changing a cab on a U model. Can you get me some pictures of that R model on the U model chassis, or any U model pictures you have in general? Thanks, Vinny

[doubleclutchinweasel]

I agree, J. It's best to start close to the mark. But, sometimes you find weird stuff!

I have a friend in the parts business who is trying to help me with this project. I would like to post his contact information, in case it would help somebody else. Where would be the best place to post that information?

[doubleclutchinweasel]

_umodelnut,

_{I will forward you pictures shortly of the two oddballs.}

[umodelnut]

_umodelnut,

_{I will forward you pictures shortly of the two oddballs.}

Ok, Thank You, Vinny

[doubleclutchinweasel]

Vinny, the files are pretty big to upload many of them. Is there any particular angle or detail I can try to upload? Or would you like me to send you some directly?

Kent

[doubleclutchinweasel]

All,

Here is one of the oddballs I saw. This truck is an F685T (both on the frame and on the...uh..."transplanted" VIN plate. The cab is an older CA36 "steel dash" piece, and the hood is a somewhat later model with the external grille on it. So, it's kind of a mutt.

"Dale" at the mack museum said that the majority of the holes in the frame for locating the various components were common, and that things like cab mount brackets were model-specific.

The reason I am asking if anyone has personally dome this swap os that I have found F-model trucks with good frames, but little else, and may have located an R or two which need frames.

Of course, like j hancock said, I would be infinitely better off if I could locate an R that is equipped the way I want. I'm just trying to keep my options open!

Kent

[doubleclutchinweasel]

Vinny,

This is the U685ST (on the frame VIN and the door plate) which has been converted to an R model.

It is in the Norfolk, VA area. Last time I spoke with the owner, he was writing out a bill-of-sale, so it may well be gone.

Again, makes you think...doesn't it?!!

Kent

[umodelnut]

Vinny,

This is the U685ST (on the frame VIN and the door plate) which has been converted to an R model.

It is in the Norfolk, VA area. Last time I spoke with the owner, he was writing out a bill-of-sale, so it may well be gone.

Again, makes you think...doesn't it?!!

Kent

That was on trucktrader, I saw that. Did you say you have U model pictures you can send me personally? That would be cool. Also can You please get me the 75' U models serial number off that truck? I would love to know the serial number.

[David]

Welcome to another Tarheel!

I have a "Mack Engineering Publication" dated 12/78 that shows the frame for the R400-600, R700ST, and U600-700 are all the same. The F700, R700S, RD400-600-700, DM400-DM600, DM800, RM4004-RM6004, DMM600-DMM6006-RM600, and RM6006 are all different. One thing you will want to pay particular attention to is the combination of the front engine mount, front crossmember, spring hangers, and raditor mounts. Most of those changes came in the '80's with air ride cabs, front mounted aftercoolers and aluminum front covers on the engines.

[doubleclutchinweasel]

That all makes perfect sense, David. The DMs are definitely a differend frame, as are the "western" trucks.

It is surprising that some of the 700s were the same, while some of them were different, though.

Thanks for the info!

Kent

[David]

The R700ST was the same because that truck was most likely a tractor. The R700S was a 10.5" frame. 1.5" higher than the others and most likely a straight job with more after frame.

[doubleclutchinweasel]

The R700ST was the same because that truck was most likely a tractor. The R700S was a 10.5" frame. 1.5" higher than the others and most likely a straight job with more after frame.

Duh! I didn't look too closely at your numbers, did I? Totally missed the fact that you were comparing a 700S to a 700ST. Eyes must be getting old! And then, there's that liquid corn effect...

LOL!

Kent