binding in 4 wheel drive only

[gevans]

I have a stock 1974 fj40 when i drive in 2 wheel drive no problems when i engage 4x4 occasionally IN THE SAND it feels like the drivetrain binds up but it releases instantly with a small "clunk" sound there is no regularity in it just occasionally with no reguard to if the drivetrain is in a bind at all. I have checked the u joints and bolts in the driveshaft they all are ok i was thinking about the front end and that scares me any help would be appreciated. Thanks Gregg

 

[John Smith]

I have a stock 1974 fj40 when i drive in 2 wheel drive no problems when i engage 4x4 occasionally it feels like the drivetrain binds up but it releases instantly with a small "clunk" sound there is no regularity in it just occasionally with no reguard to if the drivetrain is in a bind at all. I have checked the u joints and bolts in the driveshaft they all are ok i was thinking about the front end and that scares me any help would be appreciated. Thanks Gregg

Are you engaging your 4wd and running it on dry pavement? If so, you are binding the drivetrain and asking to break something.

 

[chinrednek]

You have no differential between the front and rear wheels. The front and rear wheels turn at different speeds. On dirt and snow, the wheels just slip. On pavement, you get the wind up and release. Don't use 4wd in the dry.

 

[yzftaco]

Umm If you have the correct gearing in the diffs... the wheels DO turn at the same speed... (front and back)
Now if you're talking about while in a turn than you are correct..

You have no differential between the front and rear wheels. The front and rear wheels turn at different speeds. On dirt and snow, the wheels just slip. On pavement, you get the wind up and release. Don't use 4wd in the dry.

 

[amaurer]

Umm If you have the correct gearing in the diffs... the wheels DO turn at the same speed... (front and back)
Now if you're talking about while in a turn than you are correct..

... or going over a bump, or have slightly different tire pressures, or different tire wear, or really any time you're driving a real vehicle on anything less smooth than a sheet of glass...

So the wheels pretty much never turn at the same speed.

 

[Michael Hanson]

Lock out hubs could be going out. Mike

 

[yzftaco]

You guys must be engineers...


As a machinist, I'll tell you that unless you make a tight turn you're not going to break anything.. Driving in a straight line with it engaged on pavement is best..

Legal disclaimer: I do not recommend taking long drives with 4X engaged, Although I have done it with no problems.. I am in no way responsible if you try it, and break something on your rig.. since i can't control how other people drive..

 

[amaurer]

You guys must be engineers...


As a machinist, I'll tell you that unless you make a tight turn you're not going to break anything.. Driving in a straight line with it engaged on pavement is best..

Legal disclaimer: I do not recommend taking long drives with 4X engaged, Although I have done it with no problems.. I am in no way responsible if you try it, and break something on your rig.. since i can't control how other people drive..

Noooo don't say the "e" word on this forum!!! Now no one will take me seriously!

Still, consider a situation where your front tires are worn by just 1/16" more than the rear ones (like mine are, since I adjusted my toe-in like a jackass):

With 31" tires with 4.11 gears, there will be a full turn of binding between the front and rear DS by the time you've driven 500 feet.

Your tires will probably slip on most surfaces enough to release that... until that one trip when they don't. Oops.

 

[yzftaco]

yeah that would be ugly..

ok, enough hi-jacking.. back to the original program..

 

[camcruiser13]

youll be fine


run it.


i do it all the time from trail to trail

 

[camcruiser13]

do you have a locker of any kind? that you know of?

 

[gevans]

Thanks for the responses sorry i did not put in the original post this was in soft deep sand (sugar about 8-10 " deep) i will try to answer questions posted above in this reply I have only ran 4x4 off road this happened last weekend in soft sand (ie sugar) tires have wear on them but fairly even i have no locker it does have the selectro hubs on it. only time i ran on the road in 4x4 was 4 hi on icy road never has done it before that i noticed but it is slight i was the only one that thought it might be mechanical everyone else thought i hit a stick or something but that was not the case as far as i know Thanks and keep the suggestions coming i will get to the bottom of it soon i hope ps i tried to recreate this in the mud at home later and could not do it...... huh sand maybe..... idk

 

[Fast Eddy]

With 31" tires with 4.11 gears, there will be a full turn of binding between the front and rear DS by the time you've driven 500 feet.

I claim shenanigans.

399.094 vs 399.26; how, again does this translate into a full turn of binding? Show your work student.

 

[mattcamp]

I bet his front tire turned like 5 or 6 times more than the rear one or something and then pop

 

[amaurer]

I claim shenanigans.

399.094 vs 399.26; how, again does this translate into a full turn of binding? Show your work student.

Oh no you didn't...

Distance-to-rotation function for wheel 1 and 2 (x=pi*Diameter*turns):

x1=pi*31"*t1
x2=pi*30.875*t2
(Note that I took "1/16" of wear to mean 1/16" down from the natural surface, so thats a diameter decrease of double: 1/8")

DS rotation as a function of wheel rotations (duh):

DS1=4.11*t1
DS2=4.11*t2

Combine the two to get distance as a function of DS rotation:

x1=pi*31*DS1/4.11
x2=pi*30.875*DS2/4.11

Rearrange to solve for DS1,DS2:

4.11*x1/(pi*31) = DS1
4.11*x2/(pi*30.875) = DS2

Solve for the point where DS1 differs from DS2 by one turn when the wheels do not slip (e.g. x1 = x2):

1 = DS1 - DS2 = 4.11*x1/(pi*31) - 4.11*x2/(pi*30.875)
1 = DS1 - DS2 = 0.04220*x1 - 0.04237*x2
1 = DS1 - DS2 = 0.04220*x1 - 0.04237*x1 (<-- implement no slip condition x1=x2)
1 = DS1 - DS2 = -1.7E-4*x1
5882 = x1

Convert 5882 inches to feet... (you should be nervous by now....)

5882/12 = .............


....



x1 = 490.1961 feet

For the record, yes, I am a rocket scientist. WHO ELSE WANTS SOME!??!?!

 

[camcruiser13]

Oh no you didn't...

Distance-to-rotation function for wheel 1 and 2 (x=pi*Diameter*turns):

DS rotation as a function of wheel rotations (duh):


Combine the two to get distance as a function of DS rotation:


Rearrange to solve for DS1,DS2:


Solve for the point where DS1 differs from DS2 by one turn when the wheels do not slip (e.g. x1 = x2):


Convert 5882 inches to feet... (you should be nervous by now....)






For the record, yes, I am a rocket scientist. WHO ELSE WANTS SOME!??!?!

oh snap son


all i wanted was change for a ten

 

[Krusty]

Have you had your front driveshaft out recently? If the slip joint separates and is reinstalled one tooth or more off, you can get a clunking sound as the u-joints bind and release as the shaft turns.

Good luck.

Krusty

 

[Pighead]

For the record, yes, I am a rocket scientist. WHO ELSE WANTS SOME!??!?!

NO! No mas! No mas...

 

[John McVicker]

Amaurer, I will look at your posts in a new light.

Kool.

John

 

[GarageRat]

For the record, yes, I am a rocket scientist. WHO ELSE WANTS SOME!??!?!

Where's the simulation showing the binding

The equations all look perfect, results are interesting.