I may have screwed up my 1620 HST

ETD66SS

Member
I have only mowed 3 times with my "new" tractor this spring, unfortunately today I mowed about 2 acres with the parking brake on. The tranny got so hot the plug with the little cotter pin head sticking out started to drip transmission oil. Oil was all over the mid mount mower deck.

What kind of damage could I have done besides shortening the life of the brake (pads?) The engine never overheated, the temp stayed out of the red on the guage. But I was wondering why the temperature was as high as it was, it was not that hot out today (80F)

I'm assuming the brake applied is what heated up the oil and not the pulling load, as I could not even tell the difference with the brake on...

The oil is dripping out the hole in item #24 of the following parts list. The HST unit is in that housing from what I can tell. Do you think I blew out a seal on the HST or worse?

http://www.infinity-universe.com/~dev/WhiteDwarf/Projects/1620/1620-HST-Leak.pdf

I let the tractor cool for a few hours, topped off the tranny oil, and started it up. The tractor drives fine, but there is a steady drip out of that hole while it is running, and while it is turned off. That case is filling up with oil, which I assume is leaking out of the HST unit.

What a bonehead mistake...
 
Ok, so went back this morning after the tractor completely cooled off. Removed the case drain plug, and started it up. Pretty much right away oil started to drip out.

So either the relief valve did't close back up all the way, or I burned up a seal, or worse, the heat cracked a housing (sure hope not).

Question is, should the tractor be split immediately, to see what happened, or is it likely it is a bad seal, and I can finish the mowing season, keeping the tranny topped off, and do this repair in the winter?

I do not hear any odd noises when driving, and it still operates fine, just loses oil now.
 
I would say you heated up the input seal on the transmission. It is now leaking into this housing. It MAY get better but more than likely not. You can run it and see how much it is leaking.

You are finding out why I HATE equipment that has a parking brake. I much prefer a park lock. Just about every parking brake gets driven with it on at some time in its life.
 
(quoted from post at 05:50:50 05/20/12) I would say you heated up the input seal on the transmission. It is now leaking into this housing. It MAY get better but more than likely not. You can run it and see how much it is leaking.

You are finding out why I HATE equipment that has a parking brake. I much prefer a park lock. Just about every parking brake gets driven with it on at some time in its life.

Well, the dealer is going to want ~$3500 to remove the HST, re-seal & replace.

Looks like I'm going to have to do this job myself.
 
Ok, I did the repair myself.

Unfortunately I did not have my camera with me when I first pulled apart the HST unit. But it looked like a factory defect on the gasket between the HST pump housing and the port plate. The gasket was askew & torn, then the housing was bolted down. I could see the gasket was like that from the factory due to the "stain line" from it on the aluminum housing, it was not a recent event. I overhauled the HST unit completely, and reassembeled the tractor. Runs fine, no leaks. We'll see what happens when I give it a hard days work.

Here are the disassembly/assembly pictures I took of the job.

http://www.infinity-universe.com/~dev/WhiteDwarf/Projects/1620/HST/Disassembly/

http://www.infinity-universe.com/~dev/WhiteDwarf/Projects/1620/HST/Assembly/
 

I have a question for you. I just got finished splitting my 1620 and replacing the oil seals between the gear box and the dry sump where the hst is located. I thought this is where my hst leaks were coming from. After all that work I put it back together and the damn thing is still leaking, but now I believe it is coming from the hst pump like yours. Where did you get your overhaul kit for the 1620 HST pump; New Holland does not show it avalible. I'm not sure where my pump is leaking like you it appeared to be fine and it looked like the lower shaft seal running the 4wheel drive was the problem, but it was not.. Any help would be great..
My Tractor has 3500 hours on it and started leaking after pulling a heavy road grader for about a mile so I suppose it was hot as well. I don't have the money for a new tractor or to have NH do the repair. The HST is 7k from NH which is more than the tractor is worth.

Thanks Kevin
 

Sorry I never saw this and didn't get back to you.

After 4 years, the HST is once again leaking form the SAME gasket on the HST unit: http://i.imgur.com/1JjirKg.jpg

I am resorting to making my own gasket, because I believe the issue is a poor gasket design on the part of the manufacturer.

I drew up a new gasket and laser cut it our at work: http://i.imgur.com/02KzuGX.jpg

I'm hoping this is a more permanent repair this time.
 
(quoted from post at 03:20:02 05/24/16)
Sorry I never saw this and didn't get back to you.

After 4 years, the HST is once again leaking form the SAME gasket on the HST unit: http://i.imgur.com/1JjirKg.jpg

I am resorting to making my own gasket, because I believe the issue is a poor gasket design on the part of the manufacturer.

I drew up a new gasket and laser cut it our at work: http://i.imgur.com/02KzuGX.jpg

I'm hoping this is a more permanent repair this time.

Looks like the gasket got sucked in as the oil cooled. Is the housing vented?
 

I am supersized they used a gasket. Did it have a sealer are some sort of contact adhesive on one side it looks like it in one of the pix.

I see it moved to the inside :?: I have a bud that builds hydraulic pumps for living I an going to ask him his take when I can run him down...

Thumbs up 8)
 
(quoted from post at 04:55:17 05/24/16)
I am supersized they used a gasket. Did it have a sealer are some sort of contact adhesive on one side it looks like it in one of the pix.

I see it moved to the inside :?: I have a bud that builds hydraulic pumps for living I an going to ask him his take when I can run him down...

Thumbs up 8)

I was surprised when I saw the gasket sucked inwards, it has happened twice though. I assumed there would be positive pressure inside the housing, but it seems to be negative.

iirc the New Holland overhaul manual says to use grease on the gaskets, not sealer. I don't think they wanted mechanics gobbing all kinds of excess goop all over the place jamming up the variable displacement pistons.

What I think is happening is when the HST gets to a certain temperature, the housing is warping, and the gasket is getting sucked inwards. I am laser cutting more rigid gaskets, and plan to use aviation gasket cement (very small amount) to hold the new gaskets in place.
 

Is the gasket necessary to set up clearance. I would have a hard time applying grease to a gasket its just not my cup of tea... Why would you make it slick and in your case were there are only four fasteners to retain it.

I would glue one side with a small amount 3M 8001 adhesive are this on both sides of the gasket with a very small bead...

https://www.permatex.com/product-category/gasketing/anaerobic-gasket-makers-flange-sealants/

I have seen gaskets slip some sort of adhesive nailed it in place to never move again... My HST Bota is blessed with RTV it must not be a issue with Bota...
 

My bud said they use permatex 515 sealant on both sides of the gasket. He also said a metal gasket would be the way to go.
He tried to explain it has a case line that should salvage the oil I could not get a understanding of how it worked over the phone.

As for greasing the gasket he said ell NO he would install it dry if you did not want to use sealer... The case warp question came up also....

My thoughts is I would not put grease on the gasket unless I felt the need to chase it again...
 
(quoted from post at 16:36:23 05/24/16)
My bud said they use permatex 515 sealant on both sides of the gasket. He also said a metal gasket would be the way to go.
He tried to explain it has a case line that should salvage the oil I could not get a understanding of how it worked over the phone.

As for greasing the gasket he said ell NO he would install it dry if you did not want to use sealer... The case warp question came up also....

My thoughts is I would not put grease on the gasket unless I felt the need to chase it again...

It's interesting that you say metal gasket. I was wondering when I ordered the gasket, how they could come off asking $70 for it. I just got it in today, it is a metal crush style gasket. I assume I should not use any sealant of any kind on it. I guess maybe confirm that with your buddy if you get a chance :)

Here is a picture showing the original wimpy gasket on the left, my AutoCAD re-interpretation of a more sturdy gasket in the center, and the new metal crush gasket on the right : http://i.imgur.com/pfOa3Nq.jpg?1

I am definitely going with the metal one.
 

He said probably not and I agree... You see a lot of that type of gasket used on foreign applications (plenum, air intake throttle body gaskets) most seam to have some sort of a coating on them like Teflon. I have never had a issue re-using the old gasket even with out a sealer.

I think it will solve your issue.
 

What kind of pisses me off is, the rebuild kit I bought 4 years ago, had the old paper gasket in it. If I would have known, I would have bought the rebuild kit + the improved metal gasket.

I hope no one else makes the same mistake, and buys a kit that has been sitting on the shelf for 10 years, and does not have the proper gasket. Obviously the original gasket was a design flaw.

Thanks for all your help btw.
 
Hello everyone! I cannot tell you how helpful this thread has been to me.

Our 1620 had the exact same problem with the gasket in the HST being shot. We took it apart and replaced it, got the whole thing back together and now the transmission is acting up. It works in both forward and reverse but randomly stops working.

Any thoughts helpful hints on what I may have put back together incorrectly?

:?
 

CCL you want to start a new thread for this. Most users here want nothing to do with anything modern so they stay with classic view so they don't see old ones. This came up for me because I had posted to this thread back last May. I suggest that you look the transmission housing over very carefully for a vent. Virtually all gear cases are vented to prevent this problem. A plugged vent would cause this to happen.
 
(quoted from post at 05:21:43 03/30/17)
CCL you want to start a new thread for this. Most users here want nothing to do with anything modern so they stay with classic view so they don't see old ones. This came up for me because I had posted to this thread back last May. I suggest that you look the transmission housing over very carefully for a vent. Virtually all gear cases are vented to prevent this problem. A plugged vent would cause this to happen.

Thank you for your guidance on both points. I will start a new post and look at the vents. I know I accidentally bent the bolts that appear to be venting mechanisms.

Thanks!
 
(quoted from post at 11:20:02 05/24/16)
Sorry I never saw this and didn't get back to you.

After 4 years, the HST is once again leaking form the SAME gasket on the HST unit: http://i.imgur.com/1JjirKg.jpg

I am resorting to making my own gasket, because I believe the issue is a poor gasket design on the part of the manufacturer.

I drew up a new gasket and laser cut it our at work:http://i.imgur.com/02KzuGX.jpg

I'm hoping this is a more permanent repair this time.

Hi, I have the same problem and will be splitting tractor. Great info and pictures. Is there any chance I could purchase one of those gaskets you made?
 
(quoted from post at 11:22:39 06/01/17)
(quoted from post at 11:20:02 05/24/16)
Sorry I never saw this and didn't get back to you.

After 4 years, the HST is once again leaking form the SAME gasket on the HST unit: http://i.imgur.com/1JjirKg.jpg

I am resorting to making my own gasket, because I believe the issue is a poor gasket design on the part of the manufacturer.

I drew up a new gasket and laser cut it our
at work:http://i.imgur.com/02KzuGX.jpg

I'm hoping this is a more permanent repair this time.
Ok, I just read a little deeper into the message and appears new gasket kit comes with better metal gasket. I'll order up the new kit. Thanks again for pics and info!!

Hi, I have the same problem and will be splitting tractor. Great info and pictures. Is there any chance I could purchase one of those gaskets you made?
 
(quoted from post at 03:31:26 06/01/17)
(quoted from post at 11:22:39 06/01/17)
(quoted from post at 11:20:02 05/24/16)
Sorry I never saw this and didn't get back to you.

After 4 years, the HST is once again leaking form the SAME gasket on the HST unit: http://i.imgur.com/1JjirKg.jpg

I am resorting to making my own gasket, because I believe the issue is a poor gasket design on the part of the manufacturer.

I drew up a new gasket and laser cut it our
at work:http://i.imgur.com/02KzuGX.jpg

I'm hoping this is a more permanent repair this time.
Ok, I just read a little deeper into the message and appears new gasket kit comes with better metal gasket. I'll order up the new kit. Thanks again for pics and info!!

Hi, I have the same problem and will be splitting tractor. Great info and pictures. Is there any chance I could purchase one of those gaskets you made?
/quote]

Threesuns, as I posted to crazycatlady earlier, you need to start a new thread for this, as the only people who will see your post are those who posted to the original thread, and who are also on modern view. Most members here disdain anything modern therefore they stay on classic view. Go to the top of tractor talk and click on the "new topic" button.
 

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