6 wheel drive and wide tires/triples?

[Mandrewoid]

Hi everyone, I posted here in 2019 about the DMM we acquired. I'm just now a few weeks away from having it fully operational. BUT in order for it to drive through the fields in the conditions we sometimes get into, it needs a bit more rubber. 

As you should be able to see from the picture, the 680 on the left has 650/75r22.5 on the front. On the back it has 710/65r22.5 which are of course even wider. 

Ideally I'd have 710's on the back of the DMM too, although they are very expensive tires, and burn up really fast on the road. Also, they are bigger than the 11r22.5's that are currently on. Because the DMM is 6 wheel drive, I'm concerned about damaging my transfer case if I run bigger tires on the back than it was designed to operate with? Does anyone know the standard ratio of the mack transfer case?

I'm assuming there is a differential in there, because it says full time 6WD with manual locking. So the differential would allow for the rears to turn slightly slower, but it would mean more power moving through the spiders than it was meant to do. Unless they're just built so heavy it doesn't matter? 

Second, I have Dayton hubs on the back, does anyone know how to run DUAL 425/65r25 on Dayton hubs I think if it's possible, that could be an affordable solution to put as much rubber on the road as single 710's 

 

I know a guy who used to run triple 11r22.5's, but I'm not sure how he did that either. He says he welded the outside rims to the middle rim. But I don't know how he ever got the tires mounted or unmounted after that. 

Thanks for your wisdom. 

Andrew. 

More pictures on request 🙂

Edited March 24, 2021 by Mandrewoid

[mrsmackpaul]

Do you know what the transfer case is, as in brand or model number ?

 

If its the same as the ones used in Australia I might be able to track down some info

I dont believe they were all full time 6x6 

 

Paul

[Mandrewoid]

It may be hard to see from these pictures. But that truck has triple 11r22.5 on the back.  Unfortunately I think it was scrapped about 10yrs ago. Guy has 4 of them with triples and 1 or 2 with big floaters. We bought one of the floater trucks. 

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[Vladislav]

DMM had different ratios in the transfer case to supply the torque to the front axle. Front axle's diff ratio was different than rear diffs so the transfer case was designed to compensate the difference. Actually there must be (slightly) assymetrical interaxle diff used. I remember I saw multiple those ratios in some brochure and thought it could be done due different styles (vendors) of front axles used in DMM's during the production years.

Following logic you're right about 6 wheel full time must mean interaxle diff. And it would compensate some difference of front and rear tyre sizes. But usually it works well when you drive slow and not for a long distance. Otherwise the transfer case may get overheated due to constant spinning of the interaxle differential which is not supposed to be.