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F350 vs F250 rear drive line angles

37K views 77 replies 15 participants last post by  josh77 
#1 ·
Has anyone done some comparision to see if the factory did anything different on the rear driveline to account for the different blocks sizes from and F250 to an F350. I would like to find a SC longbed F350 truck I could compare some measurements to. I am wondering if from the factory the carrier bearing was mounted at different heights between the two?
 
#2 ·
Assuming you are talking 4 wheel drive trucks, I doubt there are any changes made between the 250 and 350 driveline angles. The back end of a 350 is 2" higher due to the block but the front end is also higher which probably negates any need to change the angles.
 
#3 ·
I read somewhere that the carrier bearing is dropped 2" in a F-350 extended cab 4x4. Don't know if this is true or not as I've never seen one myself.
 
#4 ·
This is exactly what I want to get determined. I will measure up my F-250 if someone will help out with measurements on a F-350.
 
#5 ·
I didn't think an OBS SC 4x4 was produced.

No matter what Ford did or didn't do you would be better off to take driveline measurements of your truck and adjust the angles as needed. This is the only 100% sure fire way to have your truck right.
 
#6 ·
Yeah thats my understanding. All SC trucks were F250s or 2wd. And I have never seen a factory SCLB F350 in anything but a dually.
 
#9 ·
Tom, I'll try to answer what ever I can. The best advice I can give is to start reading up on driveline angles. The more you undestand the better.

Strart here; Pirate4x4.Com - Extreme Four Wheel Drive. There is some very good info.

As for initial measurements, they don't really matter. Once you have all of your suspension installed that is when to take measurements and make adjustsments.
 
#10 ·
I had read that before when I was trying to do some learning on this. I did not understand how that all worked when factoring in a two piece driveshaft like we have.
 
#11 ·
Basically think of the carrier bearing as the output of the transfercase. You will want the pinion angle a degree or two below that of the output side of the carrier.

So if the carrier bearing joint is at 4 degrees down (mine is this way) set the pinion angle at 2 to 3 degrees up.
 
#33 ·
I read the Spicer Driveshaft guidlines several times tonight. There are some guidline in there for shafts with a carrier bearing.

1. The operating angle between the transfer case output shaft and the forward half of the driveshaft should be between 1 to 1.5 degrees.

2. The angle of the forward driveshaft should be the same as the pinion angle aka parallel. This arrangement then creates equal angles on both ends of the rear driveshaft. I assume this means under load so compensation has to be made for static measurements estimating the degree of pinion rotation under power.

When I looked at the diagram from the measurements I took on my truck current set up that seemed to make better sense.

The guide also provided these basic rules

RULE 1: UNIVERSAL JOINT OPERATING ANGLES AT EACH END OF A DRIVESHAFT SHOULD ALWAYS BE AT LEAST 1 DEGREE.

RULE 2: UNIVERSAL JOINT OPERATING ANGLES ON EACH END OF A DRIVESHAFT SHOULD ALWAYS BE EQUAL WITHIN 1 DEGREE
OF EACH OTHER (ONE HALF DEGREE FOR MOTOR HOMES AND SHAFTS IN FRONT OF TRANSFER CASE OR AUXILIARY
DEVICE).

RULE 3: FOR VIRTUAL VIBRATION FREE PERFORMANCE, UNIVERSAL JOINT OPERATING ANGLES SHOULD NOT BE LARGER
THAN 3 DEGREES. IF THEY ARE, MAKE SURE THEY DO NOT EXCEED THE MAXIMUM RECOMMENDED ANGLES.

This also seemed to make sense for me with the stock setup

In taking this a step futher it would seem like if you added a tapered block or shim to point the pinion angle more directly at the transfer case THEN you would need to shim down the carrier bearing to restore the pinion angle and forwards shaft being at the same angle or parallel. I could also see how shimming the carrier would be usefull if needed to fine tune getting the pinion angle and forward shaft angle into agreement.

http://www2.dana.com/pdf/J3311-1-DSSP.pdf page 13 and 14 talk about the angles and phasing the the shaft

 
#12 ·
I've already decided that when my carrier bearing needs replacing, I'm eliminating it. I will have my drive shaft made into a 1 piece unit.
 
#13 ·
I've already decided that when my carrier bearing needs replacing, I'm eliminating it. I will have my drive shaft made into a 1 piece unit.
Where would a person start looking if he wanted to do this?
 
#14 ·
OK the reason I wanted to learn more on this is as I will effectively be lifting my truck a small amount doing the RSK both front and rear.

So I can keep this straight I will split this up. On the front due to the desired design of the kit the front of the leaf spring will be lowered less then the rear adding some caster to the axle. The other effect will be that the pinion will be lowered in relation to the the amount transfer case of the lift increasing the angles and it also the pinion angle will be pointing more at the ground also increasing the angle. I think the change is about 2 degrees or so.

MY IDEA is that perhaps I should look at this 2 degree change. By simply adding a 2 degree shim to the leaf spring back, I can restore both the original caster setting and restore the original pinion angle.

I have a new front driveshaft that has the double cardan joint at the transfer case so I was looking at this information from the very good link you posted.

Proper CV driveshaft geometry is actually a lot more simple to understand than single-cardan driveshaft geometry. Pictured at left, proper CV shaft geometry is achieved when the operating angle of the CV joint (head assembly) is less than the maximum (and there is some room for increase in operating angle under suspension droop), and the operating angle between driveshaft and pinion is 0 under cruise throttle.
This is because of the clever design of the CV joint, or head assembly. If you refer back to the picture of the CV shaft components in pat one, you will see that the CV head assembly (double cardan joint) contains two cardan style universal joints and a centering yoke assembly. This clever arrangement serves to neutralize the effects of the increasing and decreasing angular velocities, right at the head assembly. This relieves us of having to arrange the pinion yoke operating angle to be equal to the transfer case operating angle. Instead, the pinion is arranged so that the operating angle between it and the driveshaft is zero degrees (0°).
I have read any reports of issues from that 2 degree change but it also seems to me that retaining a closer setting to the factory specs would be the most beneficial for something so simple to do at the time. I have located inexpensive steel 2 degree shims so that is not an issue.

I would like to discuss this further and then maybe move onto the rear changes going from a 2 inch to a 4 inch block and see about the carrier bearing. I still want to do some measuring and comparing F250 to F350.
 
#15 ·
So will your two degree adjustment put your angle at or near zero at the front pinion? It should be in that range with a CV type driveshaft. Of course, caster takes precedence over pinion angle.

I've never measured the angles on my stock height F250 to compare the front output and the front pinion. I have a feeling that they aren't parallel because the front makes a crapton of noise with the truck in 4WD at highway speeds. More noise than my CJ5 does and it's lifted enough for 37" tires.
 
#16 ·
Well there was a TSB do address noise and vibration on the F250. The solution was to put in a dbl cardan style shaft like the F350 had. The driveshaft I picked up for my swap was actually the part number from that TSB. It might need to be changed a bit for length but the price was very right.
 
#17 ·
I seem to recall that TSB from many years ago. At the time I didn't think mine was that bad, but probably should have checked into it a bit more. With the manual transmission my front driveshaft is the shortest one used and is more prone to changes in angles compared to the auto trucks.
 
#19 ·
Forget about the transmission angle, that applies to chassis set up.

You are not going to change the angle at the transmission/xfer case with relative ease. The pinion angle needs to be addressed. You need to find the difference between the driveshaft angle and the pinion yoke.

To check pinion angle..... I use the Craftsman digital protactor. All the measurements should be at ride height. It doesn't matter if the truck is on a slope or not.
- Stick a angle finder on the driveshaft. Record that number. Say it slopes down, -7*
- Get the angle of the pinion. Either pull the driveshaft and put the protractor on the face of the yoke or put a socket on the end of the bearing cap and put the angle finder on the socket. Say the pinion angle points up 5* (nose up).

Now the difference between the two angles is 2* at rest. Which is no good under load. As power is applied, the leafs deflect and rubber bushings distort around 3*-5*. So under power, the pinion rotates above the driveshaft. What you're looking for, is to set the pinion angle lower so when power is applied, it is inline with the driveshaft.

Now with leaf springs and rubber bushings, you need atleast around -3* to -4.5* but more closer to 5* IMHO. You wanna be within 1*-2* difference under load. The u-joints can tolerate the 1*-2* difference. You don't wanna be a 0* because the needles in the yoke won't spin.

So going back to the above example, 2* is not enough. You need to buy 4* shims to place under the leafs which rotate the pinion down if you installed the shims the correct way. If you measure the pinion at rest, it should read around 1* (nose up). That makes it a difference of 6*. So under load, the pinion is going to rotate 3*-5*. This brings you within spec.

You really shouldn't play with the carrier bearing. The shaft between the carrier and the transmission/xfer case is really an extension of the transmission/xfer case.

Now throw in traction bars which "lock" the pinion angle. You can reduce that 5* difference alittle. The leaf bushings/traction bar bushings (if any) still distort.

Some don't like using shims and prefer angled blocks. Ring a bell now....why some blocks have tapers to them.

For more reading:
Pinion Angle - Wolfe Race Craft

Here is a pic of my driveshaft angle with protractor. I have my notes at my shop.



Hope this cleared some of the confusion.

Billy T.
gnxtc2@aol.com
 
#20 ·
I have the same or nearly the same angle finder as Billy so I did some measuring on mine. This is on almost but not perfectly flat gound in the garage. Every angle slopes down from left to right. This was with my truck as it sits now B code rear springs, stock 2 inch blocks, Velvet Ride shackles. The intermediate shaft has front the rear u joints in phase as does the rear but they are 180 degrees to each other phase wise.


 
#25 ·
What you guys are failing to realize, you can't change the angle of the trans/xfer case/carrier bearing w/o major mod. When you're driving down the road, the pinion angle is constantly changing. The x-fer case and carrier bearing are not moving, they're fixed.

I'll use Tom's drawing.

You drop the carrier bearing, you are going to mess up the relation between the xfer case yoke & intermediate shaft yoke.

I'm assuming the driveshaft is sloped down 5.5* and the pinion is sloped up 4.5*. So there is a 1* in the joint. I think the leaf perches on a 10.25 are welded to have 5* nose up. So it's within tolerances if there are flat 2" blocks. The transfer case and rear pinion angle almost the equal. You can't have 0*.

Now when Tom cruises or gets on it, the pinion rotates up depending on his power level. Now his 4.5* is now somewhere between 7.5*-9*. Not only does the joint at the pinion exceed it's tolerance but also messes up the angle at the intermediate yoke. And also his pinion doesn't match the t-case.

The amount of pinion rotation depends on condition of the springs, bushings, power level, towing/not towing, traction bars/no traction bars, etc, etc.

So Tom orders shims or angled blocks to rotate his pinion 3.5* down. Tom gets his pinion to 1* nose up. Now when the power is applied, the pinion rotates back up to 4.5*-5.5*. Which now puts it back in line with the T-case.

Tom, if you're still confused, give me a call tomorrow and I'll try to explain it to you, I'm working days.

Watch this video of what happens to the pinion. Don't concern yourself with the traction bars, thats a whole 'nother topic.


Billy T.
gnxtc2@aol.com
 
#21 ·
Billy, pinion angle should be compared to the TC output angle or in our case at the carrier bearing angle not the drive shaft angle. The reason one needs to check drive shaft angle and pinion angle is to ensure the drive shaft is not at such a steep angle as to bind the universal joint.

Only when using a double cardan, such as the front shaft, does one compare the angle of the angle of the shaft to the angle of the pinion.
 
#23 ·
I also did some looking to compare the carrier bearing bracket heights between and F250 and F350. It appears the carrier bearing is mounted at the same point behind the T case from the photos I have with the F350 having a longer final driveshaft. It also appears that the F250 a taller bracket and the F350 a shorter one. I forgot to measure mine tonight but will tomorrow. Could someone please measure up an F350 one for me to satisfy my curiosity and also the length of the intermediate shaft center cup to center cup? I have more photos if anyone is interested.

My F250



A F350 I found to take a picture of.


 
#24 ·
#26 ·
Billy, no one is trying to change the TC or carrier bearing angle, they are being used as reference points to set the pinion angle. Additionally Tom is trying to find the differences in the f350 angles as compared to the 250 angles.
 
#28 ·
When does carrier bearing shimming come into play?
 
#30 ·
Can you explain. Today was busy with work so I did not get to read like I wanted to but I am still confused. It seems like there are quite a few diverging opinions on this.
 
#31 ·
Ujoints can only take so much angle in the driveline before they start to bind. If you add lift you increase the angle that the ujoint has to absorb. Once you get to a certain height you need to rotate the pinon and/or drop the carrier bearing to reduce the angle.
 
#34 ·
Keep reading and before long you will be the resident subject matter expert when it comes to drivelines.
 
#35 ·
With the stock 2" blocks and the 1 inch longer Velvet Ride Shackles



With the 4" F350 blocks installed and the Velvet ride shackles removed which are 1 inch longer then stock loaded.



Does anyone think I need to tweak the set up? I went a little soft on the U-bolts torque in case I needed to make a change. I might feel just a tad of vibration on take off. Note I do have single bar traction bars but they do have a joint with some flex in both ends.
 
#36 ·
What did you ever discover on the f250 f350 carrier bearing differences?

I would probably drop the carrier an inch and see where you end up with the shaft angles and feel.
 
#37 ·
I forget to get measurements off Matts F350 when it was here yesterday. I will have to get back with him to compare some more this week.

I am surprised how much changing those blocks changed the angle of the driveshaft.
 
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