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I have a 94 F250 351w with a Dana 60 solid front axle that i put in it .... Whenever i put it in 4WD it works fine and drives fine at LOW SPEEDS like in granny gear. But as soon as i go on the road in 4WD and gain some speed, my whole tuck vibrates and it sounds like a jack hammer in the transfer case area and down at my locking hubs. But when my truck is in 2WD there is NO problem ... I was thinking maybe my transfer case AND locking hubs are bad, but Ive also been told that maybe the U joints are bad on the front shaft ... Does anyone have any idea what the problem or problems may be exactly? Any help is greatly appreciated ... THANK YOU
When you say "on the road" do you mean a paved road? Are you aware that you cannot use 4wd on clear pavement or even a packed dirt road unless only going a short distance in a straight line? Snow covered roads and offroad is fine because it allows some slip that is necessary to prevent binding in the driveline that occurs when the vehicle is turned.
Another concern would be the gear ratio in the two axles since you say you changed the front axle, these gear ratios must match or be within a couple percent of the same ratio, for example if the rear is 3.55 the front is usually 3.54. You cannot have 4.09 gears in one axle and 3.55 in the other.
Lastly.. bad U joints in the driveshafts and axles will cause vibration and maybe some noise if they are really bad but it sounds like your problem is a bit worse than that.
And it does the vibrating and noise just going down a snow covered road in a straight line ... i had the axle and hubs professionally installed so i don't know what the problem could be
Ok.. sounds like something is seriously messed up with the front axle or t-case, did the 4wd system work smoothly before the SAS? Dried up U-joints are the usual suspects with vibration problems, as a test I'd drop the front driveshaft, lock the front hubs and take it for a spin, if the vibration is still there then you know the problem is in the front axle, if it's not then the problem is with the front driveshaft or t-case
I don't know anything about this SAS so I can only ask what I would guess might be problems.
Are the 2 drive shaft U joint angles the same or as close to it as possible?
Are they in line with each other?
Is the drive shaft hitting/rubbing the skid plate/crossmember?
Did you have change the drive shaft, modify the old one?
Is it too short, over extending or too long, thus bottoming out during a suspension cycle?
Have to ask how sure are you, are you going by what you were told, numbers on the differential cover, or have you actually checked the ratios?
I'm assuming the rear axle is stock, it's unusual for a F250 to have 4.10s stock, most are 3.55s.
Originally Posted by Conanski
Ok.. sounds like something is seriously messed up with the front axle or t-case, did the 4wd system work smoothly before the SAS? Dried up U-joints are the usual suspects with vibration problems, as a test I'd drop the front driveshaft, lock the front hubs and take it for a spin, if the vibration is still there then you know the problem is in the front axle, if it's not then the problem is with the front driveshaft or t-case
I'd suggest a simpler step first, put the transfer case in 4wd but leave the hubs unlocked and go for a drive(with the front driveline in). This way everything will spin but have no load, the results will say a lot.
Originally Posted by *2fords*
I don't know anything about this SAS so I can only ask what I would guess might be problems.
Are the 2 drive shaft U joint angles the same or as close to it as possible?
Are they in line with each other?
Is the drive shaft hitting/rubbing the skid plate/crossmember?
Did you have change the drive shaft, modify the old one?
Is it too short, over extending or too long, thus bottoming out during a suspension cycle?
All good points, for example for the most part F250s don't have the double cardan U-joint at the transfer case, but the F350s do. This is cause even with the high pinion D60 the front pinion yoke is much lower with the D60 even at stock height(2" taller then F250) making the driveline angle much steeper. It's fully possible that the U-joint at the transfer case is at too much of an angle if the F250 front driveline was used.
However FWIW the driveline/U-joint angles won't be the same, it's just not possible. Another reason for the double cardan U-joint.
My truck also has a 6 inch lift in it if that helps with any solutions you may have, and my truck is a Heavy Duty F250 with the free float rear axle and from what ive read they had 4.10 ratios ... I also have tryed both locking my hubs in 2wd and going down the road AND going in 4WD without the hubs locked and BOTH times it vibrated and made noise and rattled ... if this helps any ive had my right front wheel lock up going down snowy roads when ive had it in 4wd with the hubs locked, and i know its not suppose to do that lol
Did you dismantle and service the D60 before installing it or did you just bolt it in there?
What is the axle code on the drivers door pillar calibration decal? You can't just assume the truck has a particular gear ratio there was a range of ratios available for these trucks.
Ill have to look .... but say my rear axle doesnt have a 4.10 gear ratio, would i be able to get differentials that i can swap into it to make it a 4.10 ... basically if it is wrong then how would i get the to match what would i have to do ?
Picture isn't exactly right but can give you enough to go off of. The top is a double cardan joint, the bottom isn't. You should have a double cardan where the front driveline attaches to the transfer case. This is what Brad means by two joints vs. three joints. The double cardan is two plus the one at the axle is a third.
That it does the same thing with the TC in 4 and hubs unlocked, or TC in 2 and hubs locked says it's not a gear ratio thing. However, you should check to make sure, just do a rotation count.
I think it's time to take out the front driveline, likely it's the problem and if you can't get it to do it with the driveline out then it confirms that's the problem. It may even be a length thing, with 6" of lift it's likely that the stock front driveline is also too short. More so if you used the F250 driveline.
