What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Lets discuss the solid motor/tranny mount issue again

Well, I can't speak for "most", but I can say I had no loose bolts (full inspection before the run), new mounts, and shafts that could not have bottomed. I also had a skid plate that fully covered the entire transfer case stack and the tail of the transmission, so no impact damage. I do agree that most breakage is from bottomed shafts or impacts on cases that hang down, but I don't think that was the case with mine.

But, I suppose it could have been a cumulative thing... I did hit the case before I ran my current skid and stripped the bolts out of the back of the transmission. When I heli-coiled them back, there was no sign of other damage, cracks or otherwise…

Also, just before mine broke, I has "getting it" on a large waterfall, bouncing and getting air under all 4 tires. So with 4.5 psi in 42" tires, double low range, add in bouncing around under heavy throttle with the tires coming down and being wrapped around rocks while spinning, and I'm sure you can see that the torque load would be pretty high. Street trucks don't experience those shock loads since the tires break loose long before the numbers get that high.

I'm not sure about the inertial swaging theory in my case either, other than fatigue. My rig was near vertical during this, so most of the inertial loads were along the length of the assembly, no perpendicular to it.
 
Yea, I would say that your experience was an exception. Its nice to see that people actually check their rigs before they wheel them, most people I know do not.
 
Tim, Street rigs don't use 4:1 low range and do full throttle assualts on rock. Of course they don't break things because of torque.
I doubt that frame flex plays as big a part in this as everyone thinks, as long as you have reduced frame flex in some manner semi solid is probably good. I have done nothing for frameflex in my truck and have more wheel travel from frame flex than I do from the suspension. I have the doubler mounted off of the mounting feet, single stock trans mount, and stock Ford motor mounts. I have been known to do 4:1 rear wheel drive burnouts while towing the buggy with this set up. /forums/images/graemlins/whistling.gif
I personnally feel that it is all in the mounting. Like stiffness, mounts front and rear for vehicles that get beat hard.
 
[ QUOTE ]
Guys are breaking trans/t-cases regularly? You see it happen to one guy and now its a regular thing? I rarely hear of anyone breaking trans and tcases, and I would bet that usually its due to a worn or loose mount, loose bolts either in the trans to tcase adapter, or a driveshaft bottoming out. Just MHO.

[/ QUOTE ]

Certainly not.

Long before I ever met you, Dan, or even anyone from CK5 I was still on the trail. This has been an ongoing thing too--this isn't a new problem in 4wd.

GM addressed this issue many times, with different ideas tried to stiffen this connection to make the adapters live.

The only thing that makes me take a particular liking towards this subject is that I run a 465/205 10 spline which, in my past experience, cracks more than any other adapter.

As to Dan's, there were a combination of factors involved. I think that the crossmember is what caused all that torque to twist and break his, and I'm not ruling out the idea that his driveshaft didn't bottom out eitehr because his springs were really hopping hard and I have no idea how much slip spline travel he had available to keep him from bottoming it out.

I think Dan's breakage was due to an issue like you mentioned...poor retention at the crossmember or the driveshaft, or both.

But, in the past I've seen many a rig break a 465/205 adapter, and as a result, I am glad we are having this discussion so stuff like this in the future can be avoided by all of us.

This isn't a new problem, or a completely uncommon problem...this happens on a regular basis.
 
Hey Russ, how much drag do you think you get on the square shafts when they're under torque and have to compress? It could be substantial. I heard from a fairly reliable source that a big part of the rear suspension design on the trophy truck and CORR4 he was pitting for was eliminating driveshaft plunge since 800 hp going through the splines on the shaft tended to bind up the slip shaft. We could be experiencing the same problems due to our large torque loads and in your case in particular, the square tube could have more bind in it that a splined slip.

If you were on it and fell backwards (downhill) when the front landed it could have tried to torque the pinion down and shove the axle forward hard enough that it could put a large tension load on the front driveshaft. That's something to consider anyway.

I haven't considered driveshaft plunge an important part of suspension design so far, short of keeping it reasonable so you don't have to use a super long slip 'shaft, but maybe it's a bigger deal now that we're using big power to go with our super strong drivetrains, big tires and ridiculous terrain.
 
Hmmm, good point. Had not considered that. All I can say is that I have not noticed any sign of galling or excessive wear that I would expect with binding like that, but that could explain some of the breakage...
 
some snippage from various posts....

[ QUOTE ]
If flex was so good in the frame then why did they get away from that concept?

[/ QUOTE ]

It wasn't good, it was what the accountants were willing to pay for. Every single Engineering decision made by an OE has cost involved. A savings of 50 cents per unit is huge when you look at the volume of units to be produced.

[ QUOTE ]

It's not that they *wanted* it to flex, or that it's good. It's that they had to work within the design parameters, and those requirements resulted in a ladder frame chassis being the logical choice. They knew that it would flex, so it was built to deal with it. You can see evidence of that throughout the chassis.

[/ QUOTE ]

Witness the riveted crossmembers. Those joints can flex where a welded joint can not.

[ QUOTE ]
And FWIW, even the newer boxed frames flex, just not as much.

[/ QUOTE ]

Been there, fought that in a DuraMax on King's and 37" BFG Bajas that sees high speed use in Baja.

[ QUOTE ]
Dear god, I've been sucked into one of these debates again. I've got to start ignoring these.

[/ QUOTE ]

What fun would that be?

[ QUOTE ]
I'm not exactly sure how you could calculate those forces though. Any ideas? I'd say that the dynamic load of bouncing is going to be so high I doubt you can calculate it.

[/ QUOTE ]

F=MA Figure on at least a 2G acceleration, could go has high as 4 or 5 as a WAG.

[ QUOTE ]
Basically if you just dropped the truck really hard from a few feet up and landed on a rock (that sounds familiar) does the tranny have enough inertia to break itself?

[/ QUOTE ]

My estimate is Yes.

[ QUOTE ]
Can any engineers on the site run some FEA on our frames? I dont know how difficult that would be since I have never done it, but if one could get the exact dimensions of the frame and any other pertinent info I wouldn't think it would be too hard. Correct me if I am wrong.

[/ QUOTE ]

First you need a math model (3D CAD file) to import in the FEA software. Then you need to constrain the model. That requires assumptions. Now you're screwed unless the person doing the work has a really good intuitive idea of what is happening. That takes both time in the field and time on the computer running iterations.

[ QUOTE ]
I heard from a fairly reliable source that a big part of the rear suspension design on the trophy truck and CORR4 he was pitting for was eliminating driveshaft plunge since 800 hp going through the splines on the shaft tended to bind up the slip shaft.

[/ QUOTE ]

About 2 years ago I designed a 4 link for a Class 3 race truck. The owner specifically requested two things of the linkage design. That the slip distance be held to an absolute minimum, and that all 3 UJ's always operate at the same angle. The UJ request stems from his observation that most designs with a CV at the t/c tend to employ very high angles in the UJ pinion, and those are the ones that always get broken.
 
Always good to hear from ntsqd...

Stephen:
Thinking more about what you said. I also folded a rear leaf just before the breakage, which given the bind that would have been on the shaft from impact induced torque recoil, and the axle moving several inches forward at a high rate of speed/acceleration, might well have driven it into the back of the tcase.

I think this is the most likely explanation for my breakage yet... /forums/images/graemlins/waytogo.gif
 
I'm kind of interested in this linked up class 3...
Total post highjack so maybe we get a new post or a PM? I've been mentally aaaaaah, well, pleasing myself.... with ideas on linking up a K5 for class 3 racing. I hate the idea of linking it up and having to use leaves for springs but the rules are what they are. Details?
I've had problems getting less than 2-3" of plunge on the rear driveshaft but then for our vehicles I haven't put it high on the priority list, past being able to use a standard slip shaft with 3" or so of travel. I think you might sacrifice some anti-squat properties to make this happen, depending of course on what you want for anti-squat.

Back on topic, I don't know a good way to test plunging forces without some elaborate test fixturing but it's good to keep in mind I think. Time for links for yet another reason.
 
Been listening to Sammy? /forums/images/graemlins/laugh.gif

[ QUOTE ]
Time for links for yet another reason

[/ QUOTE ]
I'll say, more like "past time"... /forums/images/graemlins/crazy.gif I've broken a set of springs (at a minimum) on each of the last two trips running. Last set only lasted about 4 hours. <sigh> They used to last several months... Now it looks like my slacking on getting the links done is likely what cost me this transmission... /forums/images/graemlins/doah.gif

[Edit]
I just started another thread to cover this topic. Anyone who has anything else to add, please make further comments on this over on the other thread rather than taking Neil's thread further off topic. Thank you...

New thread
 
[ QUOTE ]
Been listening to Sammy? /forums/images/graemlins/laugh.gif

[ QUOTE ]
Time for links for yet another reason

[/ QUOTE ]
I'll say, more like "past time"... /forums/images/graemlins/crazy.gif I've broken a set of springs (at a minimum) on each of the last two trips running. Last set only lasted about 4 hours. <sigh> They used to last several months... Now it looks like my slacking on getting the links done is likely what cost me this transmission... /forums/images/graemlins/doah.gif

[Edit]
I just started another thread to cover this topic. Anyone who has anything else to add, please make further comments on this over on the other thread rather than taking Neil's thread further off topic. Thank you...

New thread

[/ QUOTE ]

I wouldn't say you took the thread off topic. I think this is valid information. I think I will just be the test bunny for using solid motor/tranny mounts.

The Jest is, I need to stiffen the chassis via the addition of a cage (done deal) and keep in mind the information on the "driveshaft torque to spline slippage factor"!

/forums/images/graemlins/thumb.gif

Now, Watson - keep us posted on this Class 3 truck! /forums/images/graemlins/pimp1.gif
 
You must log in or register to reply here.

Latest Posts

Top Bottom