CAT mounts and slope thru drivetrain

[coachgeo]

Got the new rear Intermediate axle temporary bolted in. Tweaking things for best overall alignment of drive shaft tranny to powerdivider.

Ran into something my fabricator is finding odd.... In all his experience from standard one ton trucks to race car chassis building... the straight line thru the engine crank to tail end of tranny at the u joint is usually set at 3 degree downslope compared to the chassis. Well on this truck it is a one degree up slope. This could be normal for this truck being that it is a much larger than an one ton truck??? orrrrrrrr.... something is amiss??? Maybe engine mounts sagging pulling engine down and sloping things behind it up?? They don't look terribly bad... but then what is good?

Here is the engine mounts


Driver


Passenger.

what is ya'lls thoughts?

 

[Smike740]

I recall reading in the research done by the army into the driveshaft issue the engine angle mentioned. I don,t recall the specific number. Also I believe the angle is a compromise between the front and rear driveshaft. With the front being shorter the angle is worse.

i will look at my mounts and see what they look like today.

 

[coachgeo]

actually would love to get the driveline angle of the 6x6 as well.

 

[Ronmar]

Mine is about half a degree upslope toward the rear(front of engine lower). I think Smike 740 is correct. Pitching the front of the engine up makes life harder for the shorter front driveshaft and its ujoints in a 4X4...

 

[Awesomeness]

If you read the engineering reports about the original driveshaft issues carefully, they talk about it in one of them. The reason the engine is tilted at an unusual angle is to allow the engine to keep pumping oil while meeting one of the design criteria that it needs to be able to ascend or descend a steep slope. The report talks about how it's a contributing factor to the poor driveline angles, and I think I even remember them trying to do a test with it changed.

 

[coachgeo]

Mine is about half a degree upslope toward the rear(front of engine lower). I think Smike 740 is correct. Pitching the front of the engine up makes life harder for the shorter front driveshaft and its ujoints in a 4X4...

Yeah; the engine/tranny up slope at same degree you found is what we were finding too... threw us for a loop.

Now to degree the rear axle a tit to keep its yoke angle and tranny yoke angle appropriately matching. Makes since engine/tranny NOT having typical down angle that would then cause more issues with front shorty driveshaft...... we get enough vibe there as it is.

 

[Jbulach]

Whats the degree of your front axle pinion, is it an acceptable angle with the t-case output?

 

[coachgeo]

Yes

 

[Jbulach]

I’d call it good, it sounds like your guy knows what he’s doing. The nose down pinion may look odd, but as long as the shafts are as close to parallel as possible at loaded ride height, you should be golden.