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ebnel
ebnel, Technician
Category: Heavy Equipment
Satisfied Customers: 282
Experience:  master certification diagnostics and repair
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I purchased a John Deere 4960 MFWD w/powershift a year ago.

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I purchased a John Deere 4960 MFWD w/powershift a year ago. It had just come out of the shop with a transmission rebuild. They had replaced a bunch of parts but mainly the ring gear and disks for #3 planetary brake. The symtoms were listed as "no reverse and noise in transmission." We used the tractor for planting and pulling a grain cart and this past fall, going down the road, not yet full speed, it downshifted big time by itself and started making noise and no reverse. Took it apart, and same parts are broken. It's like this planetary brake just engaged on its own and broke the ring gear and disks. Checked all the controls, everything looks good. Asked dealer, no idea yet. Don't want to replace and have happen again. What could cause this downshifting and brakage? Bill
Submitted: 4 years ago.
Category: Heavy Equipment
Expert:  ebnel replied 4 years ago.
Hello thunder, I have rebuild lots of these pst trans. Just couple questions, did all brake housings look good? No gouges or disk wear into housins? Also was shift valve on right side inspected? Also did dealer make sure all elements pressure checked good?
Customer: replied 4 years ago.
EBNEL, All the drake housings looked good except for B3, it was worn and gouged up from when the discs broke and turned inside the housing. They had replaced this housing last year so it was good at that time. I inspected part of the shift valve, I took the cover off and lifted the forward/reverse valve out and it looked good, no marks anywhere, and all conections were tight. Last year when it was rebuilt, I don't know if they did a pressure test. This year, I don't have that equipment so I did not test it. I was hoping to replace parts and put back together and save the $4000.00 labor bill. But when I see the same thing happened less than 250 hours ago, I want to know more.
Customer: replied 4 years ago.
EBNEL, one other thing, the whole "package", I think it's called the output planetary, is held it the transmission housing with four bolts, and when I got that far on diasembly, I could remove them with my fingers and you can see where the unit was working in the Transmission housin and the one locating pin was loose and bend. Those four bolts hold the unit down against the o-rings on the bottom of the transmission case. I don't know if they were loose enough to allow leakage but the o-rings were not blown out. If this makes any difference. Some times, soon before this happened, it was a little slow on some of the shifts. Bill
Expert:  ebnel replied 4 years ago.
Sorry I'm having computr issues,If your pack was coming loose that is when I seen gear failures,Replace bolts and piston packings,Also replace long bolts holding pack together, check planetary gears and bearings.Yes if you had pressure loss thats when I seen disk and ring gear failures, i will do more digging and post here.

Edited by ebnel on 2/13/2010 at 9:31 PM EST
Customer: replied 4 years ago.
I want to be clear, it was the bolts that hold the pack in the transmission case not the long bolts that hold the pack together that were loose. Is the b3 engaged for anything besides reverse. I figured it would take b3 being engaged to cause the problem, but you are saying that another one loosing pressure would do it?
Expert:  ebnel replied 4 years ago.
I would hope other dealer would stand behind their work, cause I have never seen the top bolts come loose on their own, course i always use lock tite, that entire assembly has no end pressure against it, only shafts going through, so really is no reason for bolts coming loose.I just got your last post,I will check which gears use b3. You only have 190 or so psi in pack so o-ring might not shear even when leaking
Customer: replied 4 years ago.
I deal with another branch of the dealership I bought it from ( it's now up to 10 dealerships owned by one) but the local service manager said that he would see if they could help on the parts seeing as how I'm doing alll the labor. The original warranty when I bought it was for three months.
Expert:  ebnel replied 4 years ago.
Your system oil pressure should be 170-180 psi. B3 is only engaged for reverse gears.Let me know if I can assist you more
ebnel, Technician
Category: Heavy Equipment
Satisfied Customers: 282
Experience: master certification diagnostics and repair
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