[edw]

My gearbox output shaft is seriously worn and trying to find parts is difficult. I saw a gearbox on EBay for 149.95 looks like a possible replacement size wise. The seller looks ok and he has sold a lot of these. I just want to know if anyone who has bought and installed one on a mower deck and if it’s worth buying.

 

[TempletonJDguy]

The going price on those out here is upwards to 500$ so that price sounds very very attractive.

 

[HappyValleyJD]

Last year I had to replace the 90 degree gearbox on my snow blower. I was able to find an exact replacement from Peerless Gear (www.peerlessgear.com). While this is a custom blower arrangement, they had a decent selection of right angle boxes available. I think it was in the range of $180. You might shoot them a note with the specs of what you have and need. The engineer I worked with was over-top-helpful.

 

[army]

Some commercial parts sellers don't test them so that used gearbox isn't necessarily ok. They have a good return policy instead. In some cases if a part is defective they just refund the money and don't even want the part back. Something to keep in mind is 420 gearboxes turn the opposite way to a 400 deck and are a 1:1.5 ratio. 400 decks are 1:1 so watch out for that. A 420 gearbox drive pulley is 5.5" vs 7" for a 400. I put a new gearbox on my 420 deck that spins the correct way bit it's a 1:1. The slower blade speed is pretty aggravating sometimes. I'm gonna put a 6" drive pulley on it. It will just fit and speed the blades up 14% according to the math.

The new gearbox. Had to shorten the driveshaft due to the longer input shaft. I don't know what the new one was off.

My gearbox output shaft is seriously worn and trying to find parts is difficult. I saw a gearbox on EBay for 149.95 looks like a possible replacement size wise. The seller looks ok and he has sold a lot of these. I just want to know if anyone who has bought and installed one on a mower deck and if it’s worth buying.

 

[TempletonJDguy]

Good info ☝

 

[dan_hosler]

I just went through this exercise in the past couple of months for my 60" deck. My output shaft was severely wobbled out. The culprit was a loose split bushing which attaches the sheave.

I saw only a couple of options at the time:
1. Buy used/rebuilt for $$$
2. Rebuild myself for much less money

I chose to rebuild the gearbox myself. Influencing factors in my decision were:
1. I have the time to rebuild properly due to being winter.
2. I am very wary of online replacement parts that are obviously underpriced.
3. And the biggest factor: I have partial ownership of a machine shop.

For your specific situation, you need to repair the output shaft. It likely underwent the same failure mode as mine. If you do not have easy access to a free/cheap machine shop, you may consider simply buying that output shaft new of JD. It is a $216 part, but you will have the comfort of knowing it will be rebuilt correctly and should last a good many many years.

If you choose to rebuild yourself, I also suggest replacing the shaft seals (2x) and the gear case o-rings (2x). You might have $250 total in the rebuilt if you buy that $216 part.

Keep us updated in your decision making and show lots of pictures as you go.

 

[Jeeks]

Some commercial parts sellers don't test them so that used gearbox isn't necessarily ok. They have a good return policy instead. In some cases if a part is defective they just refund the money and don't even want the part back. Something to keep in mind is 420 gearboxes turn the opposite way to a 400 deck and are a 1:1.5 ratio. 400 decks are 1:1 so watch out for that. A 420 gearbox drive pulley is 5.5" vs 7" for a 400. I put a new gearbox on my 420 deck that spins the correct way bit it's a 1:1. The slower blade speed is pretty aggravating sometimes. I'm gonna put a 6" drive pulley on it. It will just fit and speed the blades up 14% according to the math.
View attachment 287044

The new gearbox. Had to shorten the driveshaft due to the longer input shaft. I don't know what the new one was off.
View attachment 287045

I get the ratio difference but they turn whatever way you want to turn it. The 400 may power it the opposite direction but it will still work backwards.

 

[army]

Yuh. I think we all knew that. The point was the output shaft on 400 and 420 deck gearboxes turn opposite to each other.

I get the ratio difference but they turn whatever way you want to turn it. The 400 may power it the opposite direction but it will still work backwards.

 

[army]

Great info Dan and very well explained.

My 420 deck gearbox has an input shaft issue. There's enough play in it to shake the deck and the external keyway on the input shaft is buggered up too. Output shaft seems fine though. I'll rebuild that gearbox if I can. Had the spare new gearbox so I haven't dug too deep in that respect yet.

I put the new gearbox (grey one) on a 400 deck several years ago. That's when I realized it rotated the other way (aka opposite, backwards, reversed?). I flipped the blades over and tried mowing anyway just to see what it would do. It made the kind of mess you'd expect with nothing exiting the discharge chute. Likely would have worked good to mulch leaves though. Same as backing up over them but much easier on the old neckaroo.

I just went through this exercise in the past couple of months for my 60" deck. My output shaft was severely wobbled out. The culprit was a loose split bushing which attaches the sheave.

View attachment 287050

I saw only a couple of options at the time:
1. Buy used/rebuilt for $$$
2. Rebuild myself for much less money

I chose to rebuild the gearbox myself. Influencing factors in my decision were:
1. I have the time to rebuild properly due to being winter.
2. I am very wary of online replacement parts that are obviously underpriced.
3. And the biggest factor: I have partial ownership of a machine shop.

For your specific situation, you need to repair the output shaft. It likely underwent the same failure mode as mine. If you do not have easy access to a free/cheap machine shop, you may consider simply buying that output shaft new of JD. It is a $216 part, but you will have the comfort of knowing it will be rebuilt correctly and should last a good many many years.

If you choose to rebuild yourself, I also suggest replacing the shaft seals (2x) and the gear case o-rings (2x). You might have $250 total in the rebuilt if you buy that $216 part.

View attachment 287051

Keep us updated in your decision making and show lots of pictures as you go.

 

[edw]

We’ll I didn’t get a gear box for Christmas but the replies from you’ll gave me a broader perspective on what to look for when I take it apart. It was a very noisy gear box and not having a reference to other decks I will see what I find out. Will keep you posted and with pictures, thanks!