990 rear diff problem

kenmore99 · Apr 7, 2010

I've been happy with my JD 990 7year old tractor until it started knocking last week--I baby this tractor and it only has 340 hrs and now its getting a new rear differential! wow- going to pay the JD dealership for the repair and may go look at Kubota--Ive always serviced on time etc--I'm bummed--anyone else had this happen???

RoyJackson · Apr 8, 2010

kenmore99 said:
I've been happy with my JD 990 7year old tractor until it started knocking last week--I baby this tractor and it only has 340 hrs and now its getting a new rear differential! wow- going to pay the JD dealership for the repair and may go look at Kubota--Ive always serviced on time etc--I'm bummed--anyone else had this happen???

This is the first time I've read of a 990 breaking.

kennyd · Apr 8, 2010

RoyJackson said:
This is the first time I've read of a 990 breaking.

Me too...

Welcome to TBN kenmore

Can you give us some more details? What exactly broke?

kenmore99 · Apr 8, 2010

The JD dealership at first couldnt find the knock--after a week I told them to keep looking bc when it started knocking in the rear it would scare the daylights out of him--a week went by,I called yesterday and the mechanic stated he was "so busy sorry I havent called but your rear dif. is gone and I've ordered gears to replace" I told him I was upset since that sounded expensive and he hadnt cleared it with me and he stated "well,you cant drive it now bc the rear's in pieces and its not my fault it failed and I dont know the cost till I'm done"--so...my overall disposition will be determined when we see what the repair bill is...next week

Nitro-Fish · Apr 8, 2010

Doesn't the 990 have a planetary set up? I would think it would take quite a bit of abuse to damage one!

arrabil · Apr 8, 2010

Wow, never seen an axle quite like that before. Yep... its a planetary axle drive system. And I agree that looks REALLY stout. But, its still driven by one pinion from the transmission. Thats probably where it broke is my guess.

I'd imagine if the diff lock got stuck, or was used incorrectly, that planetary drive would transfer a tremendous amount of strain to the transmission pinion.

kenmore, you should ask what specifically broke... the drive axles themselves look indestructible.

[I'm perusing the 990 tech manual btw.]

kenmore99 · Apr 9, 2010

I'll ask specifically what broke--I spoke with the head service person and he said not only was the differential replaced but 2 wheel bearings also were replaced and I'll find out the total cost next week (at least 2k so far)--my only symptoms were an infrequent loud rear knock every so often out of nowhere--it never shook,stuttered,or affected the pull of the tractor--since i am mechanically illiterate, I hope I'm not getting suckered--I'm asking for used parts next week to see what the condition was and let you know.thanx--again, this tractor was babied and pampered--I'm sick

arrabil · Apr 9, 2010

my only symptoms were an infrequent loud rear knock every so often out of nowhere

That could be the differential skipping a tooth like I was guessing. Any particular reason you didn't take it in after hearing the first loud knock?

kenmore99 · Apr 10, 2010

I took the tractor in for repair the 3 rd time I heard the knock--the knock only lasted 2 or 3 knocks the first 2 times but I took it in the 3rd instance when it knocked 4 or5 times--it took the dealership 2 weeks to get it to knock again--the dealership reiterated today that the tractor would have to be pushed past its limits to strip the rear gears but I can attest that didnt happen--it will be finished repair tuesday--I looked at the KubotaL4400 yesterday and it just plain looked less sturdy/less solid than a JD410--going to pay for this over 2k repair and look the JD4105 and the MF1643--anyones opinion on those 2 trac would be appreciated...