[Someoldguy]

They are both 4X4 and the front diff is on the drivers side.

Please excuse my ignorance, but isn't the transfer case offset to match the offset on the differentials?

 

[EVguy]

Yes, they are both drivers side drop.

 

[Someoldguy]

Yes, they are both drivers side drop.

so if i understood you offset the engine to get your transfer case to have perfect alinement with the drivers side drop?.. why not center the engine and have a slight cant from the transfer case to the differentials by the drivelines?

 

[EVguy]

I'm just doing it the way it was from Dodge, the offset does not interfere with anything on the Cummins so no need to reinvent things. The diff is also very close to the oil pan so engine could not move over to center without major mods.

 

[Someoldguy]

I'm just doing it the way it was from Dodge, the offset does not interfere with anything on the Cummins so no need to reinvent things. The diff is also very close to the oil pan so engine could not move over to center without major mods. View attachment 131116

 

[Someoldguy]

thanks for the education.. I was a might confused.. Now I'll have to measure my 5.9s and see if they are offset..

 

[scout4bta]

Still got questions that need answered:

1. Are you guys mounting the engines dead-centre or offset?
2. What is the typical inside width on your frame-rails?

On my first set of mounts the isolators were centered on #2 cylinder, the engine was centered between the frame. Used 93 Dodge Diesel isolators.
My current project I'm using the Anchor 2698 (fluidlastic) isolators. The left side is forward 1.5" from center and extends 5.25" from the center bosses. Base of the isolators is at crankshaft centerline.
The right side is centered on the engine. The isolator extends 6.25" from the center bosses. The base of the isolator is at crankshaft centerline.
Distance between frame rails is 28" The engine will be centered between the frame rails.

 

[EVguy]

On my first set of mounts the isolators were centered on #2 cylinder, the engine was centered between the frame. Used 93 Dodge Diesel isolators.
My current project I'm using the Anchor 2698 (fluidlastic) isolators.

Now I'm curious. What you did not like about the Dodge mounts that made you go to the Anchor ones? I just put the Anchor 2698's in my Dakota and they work well but I'm wondering about durabillity long term with the weight of the Cummins and towing which will put lots of torque on the mounts. I had intended on using the Dodge ones with the holes drilled in them for this new swap.

 

[scout4bta]

Now I'm curious. What you did not like about the Dodge mounts that made you go to the Anchor ones? I just put the Anchor 2698's in my Dakota and they work well but I'm wondering about durabillity long term with the weight of the Cummins and towing which will put lots of torque on the mounts. I had intended on using the Dodge ones with the holes drilled in them for this new swap.

The Dodge mounts in my Scout worked very well and better with 2 drilled holes in them. There were some rpm ranges where they transmitted some vibration at cruise speed, but not enough to make me change them out. Those original mounts were still going strong when I sold the Scout last year, Altho the drilled holes had pretty much collapsed.

Why did I change to the 2698, wanted to see if I could design mounts that were more centered than my previous mounts. And the new mounts allow me to use the first gen Dodge AC compressor, easier to source from a parts store.

 

[Goat]

 

[Someoldguy]

View attachment 131282 View attachment 131283

wonderful... now if they had shown the optimal load points and mount configurations to reduce the harmonic vibrations we'd be happier than a pig in mud.......

 

[Goat]

With the numerous combinations of drivetrain & physical movement constraints?

 

[Someoldguy]

With the numerous combinations of drivetrain & physical movement constraints?

if we dampen the motor before we calculate the needs of the rest of the drive train.. I'd think we could find that the normal systems in place to dampen them would be more than adequate..

 

[Goat]

If that's the case you would be damping primary and secondary of the engine only. If you don't take the drivetrain into account you can't dampen roll frequency. It's worst at idle and happens to be the chief complaint.

94+ Dodge mounts are offset and the isolator has a spring constant of 3000lbs/in (yes I measured).

 

[Dougal]

If that's the case you would be damping primary and secondary of the engine only. If you don't take the drivetrain into account you can't dampen roll frequency. It's worst at idle and happens to the chief complaint.

94+ Dodge mounts are offset and the isolator has a spring constant of 3000lbs/in (yes I measured).

Well that's a damn good reference. Where did you find it?
Do they have diagrams showing how they intended them to be mounted? Was it 4 mounts per engine (two front, two bellhousing)?

So if we go for the soft mounting, we're looking for static vertical deflection of ~0.2 inches (5mm). We can then decide how far in the mounts need to be to give a soft enough moment to keep roll frequency below 14 Hz (I have done none of the maths yet).

How about mount orientation? Can we simply use rubber blocks on 45 degrees (I'm thinking of landrover 300tdi mounts right now) and not care about the intersection height?

 

[scout4bta]

Well that's a damn good reference. Where did you find it?
edit..........

Cummins Install Guide , see post #5

 

[Goat]

So if we go for the soft mounting, we're looking for static vertical deflection of ~0.2 inches (5mm). We can then decide how far in the mounts need to be to give a soft enough moment to keep roll frequency below 14 Hz (I have done none of the maths yet).

How about mount orientation? Can we simply use rubber blocks on 45 degrees (I'm thinking of landrover 300tdi mounts right now) and not care about the intersection height?

If packaging allows you could opt for more static vertical deflection. 0.6" (15mm) would provide 98% isolation.

With a block type mount I would take orientation into account. Intersection height is the roll centerline and when roll center is inline with center of mass, 100% of any primary unbalance & reaction torque is absorbed by the rubber. Down side is you have a lot of shifter movement

 

[Someoldguy]

If packaging allows you could opt for more static vertical deflection. 0.6" (15mm) would provide 98% isolation.

With a block type mount I would take orientation into account. Intersection height is the roll centerline and when roll center is inline with center of mass, 100% of any primary unbalance & reaction torque is absorbed by the rubber. Down side is you have a lot of shifter movement

If I read you correctly and my memory serves.. I read on here of people using the top GM engine roll suppressor to tame the vibration.. if that be the case.. maybe a bottom mount/ top mount configuration would produce premium dampening.. then someone who has actually used their brain for something other than forgetting their engineering classes of 40 years ago.. we should be able to vector out tortional forces and use this for optimal mount locations and design.. but my math ability died long ago... too many head injuries and too much booze and drugs under the hood..

 

[Goat]

Precisely Someoldguy, seems to me that your noodle still works just fine.

A torque arm is a fine solution but you could also move the roll center by changing the angle of the mounts and do away with the torque arm.

I've retired my 4bt, so I no longer have dog in the fight and I'm keeping my secret sauce recipe to myself, just too many youngbloods out there that are looking to make a buck off someone's work.

Data for an accurate model I can help with, such as, flywheel/clutch/pressure plate assembly for a 4bt is 87 lbs.

 

[Dougal]

If packaging allows you could opt for more static vertical deflection. 0.6" (15mm) would provide 98% isolation.

With a block type mount I would take orientation into account. Intersection height is the roll centerline and when roll center is inline with center of mass, 100% of any primary unbalance & reaction torque is absorbed by the rubber. Down side is you have a lot of shifter movement

The ones I've looked at had the intersection well below crank and more like front axle height. Probably just because that's the position that fits. The result I guess is side to side rocking instead of letting the whole drivetrain roll.

As for deflection. My vehicle used to have mounts on like a 60 deg angle (from horizontal) and it put the rubber mounts into such shear that they had no vertical discipline and the vertical shake from the g-outs on road was a problem that put a secondary vertical shake into the whole vehicle.

I don't have an easy way to measure hardness. But landrover 300tdi mounts are rectangular slabs of rubber, 1.5" thick and 3" square mounted 45° to an aluminium pedestal:

Doesn't look very square on the pic, but I've measured them.