JD-3520 MFWD "driveshaft" faulty?

tugboat-2 · Sep 6, 2009

My 2006-JD-3520-Cab,... just racked 900 hours and on its third,..(3rd) MFWD "driveshaft". The shaft that comes forward from the transmission to the front differential.

Its splined-end meets the splined shaft coming out the back of the front diff. The two slide into a short,(3") common, internally splined "sleeve",..(with a pin through the centre).

Load-Match and 4WD engaged constantly unless in transport or mowing. I dig and move lots of earth, "working" my machine, but never purposely abuse it.

First shaft went (last year) suddenly. The next gave a quick warning. Driving down a steep, 20ft hill, filling my bucket and "backing" up the hill all afternoon,.. no problem.

Went down scooped a 1/2 load for front ballast, scraped up a pile with rear blade,.. filled the bucket and crawling up frontwards (low gear @2500 RPM) felt a quick slip'n'grab, slip'n'grab and detected a faint clicking as I came over the top. Dumped my bucket and parked.

Slid under checking "everything" for "anything", shafts, linkage, pins etc. Removed dash panel to check "travel" and freeplay in the MFWD "lever". The "Brail-method" confirmed lever engagement of detent spring-balls that "hold" it in gear,...yet there was NO drive at wheels! Checked oil levels and anything else I could think of, All OK. The driveshaft "felt" tight.

Testing,..(smooth and quiet) in 2 wheel, but 4WD,..."Nothing"!! So dropped grader blade and bucket, connected RFM and mowed a couple hours without incident.

Next day, drove 'er the quarter mile to my dealer. The shaft and sleeve splines, were rounded off, warn and chewed like you'd expect from "softer" metal.

New shaft and sleeve wouldn't be so bad,..but the "other" shaftspline was just as bad,....EXCEPT:..it's the back end of the front "pinion" gear (one solid, short shaft) which means dropping the front axle, splitting the case, pulling out the carrier, (Crown and pinion, side gears and bearings etc), and replacing the pinion,...which is a pre-set "package" with bearings etc complete!!!

They suggested the alternative: "welding" everything solid, to save a major expense. But agreed the possibility of "heat" damage through the short pinion shaft to seals and bearings was not a good choice. (good idea on an old beat up tractor,...but WHOA!! This Baby is still brand new to me,..still shines up to a Beauty!!!) So I authorized a full and proper job. This is precision work in a clean shop with the right tools and not for my dusty, gravel floored drive-shed. (Note: no paper gaskets,..just metal to metal with liquid sealant spread thin with an ink roller and torqued! A sterile operation for the OR!!)

Meanwhile I have my tractor back, up and running,...but am walking on eggshells,..hesitant to go back to anything heavy. Perhaps having a brand new machine made me a tad "over" confident??

Well OK, now that you've endured another long winded "tug-tail",...."IF" you're still with me,......have any of you experienced anything similar?? AGAIN: This is an (Xmas) 2006 JD-3520-Cab,...(my beautiful Rolls! Cab still has that "new-car" smell,..ha,ha!)

I'd appreciate your thoughts...?
. . tug

sunnyside360 · Sep 6, 2009

I've never had a burp with my 3720 engine or drive train but I only use 4 WD when the wheels are slipping or when on a very steep hill to give 4 wheel traction and/or braking. Otherwise, it's always in 2 wheel drive which is 99% of the time. I don't recall anyone else reporting this type of problem. I personally don't think it is good for the drive train to keep it in 4 wd all the time due to the stresses put on it.

Cocre · Sep 6, 2009

Have you got a matched set of tires? From what I understand the front and rear have to be sized to rotate at the ratio of the MFD, just something to check.

RogerH · Sep 6, 2009

A couple questions:

1. Are the rear tires filled with fluid?
2. How heavy is the blade on the rear?

The reason I ask is that in my experience many angle type blades and lighter box blades are not enough weight on the back to properly ballast the tractor. When using the loader, most of the weight ends up on the front wheels and all the power is going through the front axle. This can wear out the front axle and MFWD drive components quicker.

When I take apart anything that is splined, I like to lubricate it with a "moly" grease when I reassemble it. I have read where that helps prevent spline corrosion, which accelerates wear.

tugboat-2 · Sep 7, 2009

sunnyside360: Thanks for the reply, I must agree with you on the idea of stress and keeping in 2WD as much as possible. I've been digging and climbing a lot and need the traction for both aspects. However, I'll take your advice and try to disengage 4WD when not really necessary. Definitely a good "habit" to form!!

I should (and "do") know better,...just got into the bad habit of leaving 4WD engaged due to the terrain I'm working much of the time. "Costly habit that"!!
THANKS~~~~~~~~~~~~~~~~~~~~~~~

Cocre: Thanks for the reply, and thank you for a great suggestion. I have always been cognizant of that fact and although I've changed front tires a couple times,..I'm very strict about sticking with what tires were recommended for the tractor when it was new,..they are matched but I agree that is a very excellent point, (especially for those new to 4WD!)
THANKS~~~~~~~~~~~~~~~~~~~~~~~

RogerH: Item: 1. Yes, the rear tires "only" are filled with good Canadian Beet Juice. Item: 2. Relative my rear grader blade, I'm not sure of the actual weight, but it's quite old, had it for years. Extremely heavy compared to modern ones. Was likely sold as EXTRA Heavy Duty when new.

However, you do conjur up an excellent point. The work I was doing, (and quite a bit of it), was driving forward down a fairly steep grade, filling the bucket with damp, heavy earth, . . then "backing" up the hill. At this point the weight would be on the front wheels, . . and the weight of my blade was more than likely inadequate to countre the stress?

The hill was of such steepness that more than once I stopped and rocked the tractor slightly to see if it would lift the rear and balance on the front, but not a chance. I guess the combined loaded tires and blade held us firm. (I have the two-way tiltmeter, unsure how to read the fore'n'aft but it sat on 1.5 and more,. if we have an interpreter aboard?)

Regardless, . . I see the stress I was placing on the entire front assembly as I "backed" up the hill. Climbing slowly "forward" up the hill perhaps wouldn't be quite "as" stressful but certainly too much on a continuous basis! And it "was" the forward climb that stripped the splines,...or at least was the "coup-de-grace" for them.
THANKS~~~~~~~~~~~~~~~~~~~~~~~

TO ALL of you who responded thus far: Your combined input is of great value to me (and hopefully to others), so please accept my sincere thanks!

CHEERS for now !!
. . tug

kennyd · Sep 7, 2009

RogerH said:
A couple questions:

1. Are the rear tires filled with fluid?
2. How heavy is the blade on the rear?

The reason I ask is that in my experience many angle type blades and lighter box blades are not enough weight on the back to properly ballast the tractor. When using the loader, most of the weight ends up on the front wheels and all the power is going through the front axle. This can wear out the front axle and MFWD drive components quicker.

When I take apart anything that is splined, I like to lubricate it with a "moly" grease when I reassemble it. I have read where that helps prevent spline corrosion, which accelerates wear.

I agree with Roger here...sounds like a ballasting problem.

Cocre · Sep 7, 2009

I never (well almost never) take my 3320 out of MFWD, but I also have a 1000 pound backhoe hanging off the rear most anytime I am using the FEL. I have been meaning to load the rear tires too, I will probably do it for sure now.

sunnyside360 · Sep 7, 2009

Cocre said:
I never (well almost never) take my 3320 out of MFWD, but I also have a 1000 pound backhoe hanging off the rear most anytime I am using the FEL. I have been meaning to load the rear tires too, I will probably do it for sure now.

My neighbor has a 4X10 with FEL (no backhoe) and he used to keep it in MFWD all the time until he had trouble. He had to replace some gears and bearings in the front axle housing. He now uses MFWD only when needed.
I personally am not so sure he had the problem because it was in MFWD all the time but he thinks so.

Spudland_Dave · Sep 7, 2009

sunnyside360 said:
I personally am not so sure he had the problem because it was in MFWD all the time but he thinks so.

I'm gonna agree with you, most if not all the machines I know about (friends & family) of various color pretty much LIVE with the MFWD engaged.. My dad has 900 hours on his orange L2900 and I think probably only 5 of those hours have been in 2wd...Also quite a few green machines that for all intents & purposes you could engage MFWD and then unhook the linkage...

LBrown59 · Sep 7, 2009

sunnyside360 said:
My neighbor has a 4X10 with FEL (no backhoe) and he used to keep it in MFWD all the time until he had trouble. He had to replace some gears and bearings in the front axle housing. He now uses MFWD only when needed.
I personally am not so sure he had the problem because it was in MFWD all the time but he thinks so.

I don't think so either it's something defective.
.