NV3500 Bearing Seals & Overheating
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Registered User
Joined: Mar 2024
Posts: 22
Likes: 4
From: Oceanside, CA
NV3500 Bearing Seals & Overheating
Hello all,
Simple question, do any of you run your transmission input or output bearings with one or both of the seals removed? If so, has it helped with bearing failure? And can anyone think of potential downsides to removing the seals from the bearings?
Back story: A few weeks ago, I drove 1100 miles in one day on a round trip to Arizona from Oceanside, CA to pick up a transmission and transfer case. It was a hot day in AZ, and I was in 5th gear around 80mph the majority of the trip for hours on end loaded with about 500 lbs on the back. By the time I got back home, the transmission was making a definitely noticeable bearing howling noise (similar to a bad wheel bearing but not as bad). I realize I could be wrong, but my ears and gut instinct tell me it's the output bearing. The noise is directly proportional to wheel speed, not rpm. so in my mind that rules out the input bearing. and the countershaft bearings are submerged in oil so I'd be amazed if those ever failed before the input/output bearings. And yes I checked the oil level and its full and the oil seems to be in good shape (I put it in about 8 months ago).
Hypothesis: My suspicion is that the hot AZ day, with about 16 hours of nonstop high speed driving was too much for the sealed bearing, and due to the seals, it couldn't get enough oil circulation to keep it cooled and failed. I've heard of these output bearings going bad when towing heavy in 5th for long periods. As a side note, i've also towed a 5k lb trailer for 600 miles a couple months ago with this same bearing, and no issues there. But I towed at 65mph in 4th gear where the input and output shaft are directly coupled. Therefore there is (almost) no loading on the input and output bearings since the countershaft is just idling along with no real force on any gears. This time I was going alot faster and I was 5th gear, where there is both radial and thrust loading on the bearings. (especially the rear since 5th gear is right next to the rear output bearing and therefore transmits most its radial load to that bearing).
Proposed Solution: I intend to tear apart the transmission again in a couple weeks and replace the bearings again, however this time I will remove the inward facing seal from both bearings. So they can receive ample lubrication and cooling from the oil. I will not remove the outward facing seals so that I don't get excessive oil seeping out through the input and output seals. Down the line I also intend to fabricate an oil cooling system for the transmission.
As a side note: In about a month from now, the truck will do a 1500 mile trip to Texas flat towing a 2500lb jeep through a few small mountains (5,000 ft elevation change) and mostly flat ground after that. I will also install a transmission oil temp gauge before the trip to monitor oil temp throughout the trip and see if it becomes excessive as that might have also contributed to the bearing failure. Does anyone have recommended oil? as I've been using the Pennzoil synchromesh.
Truck info: Truck is single cab short bed 2wd 5.2 1500. I have an nv3500, which I rebuilt last summer since 5th was popping out under torque. Anyhow, I replaced all the bearings and seals as per the usual. The bearings which came in the kit were sealed bearings like the original ones I took out. The rebuild went well and I've put about 15k on it so far with about a 1k of towing heavy with a few steep grades, and often carrying 300-900 lbs on long drives. Aside from that, easy daily driving. The truck is bone stock including 245/75r16 ties and stock gearing. I don't drive aggressively but I sure put her to work.
Thanks for any input and experience.
Simple question, do any of you run your transmission input or output bearings with one or both of the seals removed? If so, has it helped with bearing failure? And can anyone think of potential downsides to removing the seals from the bearings?
Back story: A few weeks ago, I drove 1100 miles in one day on a round trip to Arizona from Oceanside, CA to pick up a transmission and transfer case. It was a hot day in AZ, and I was in 5th gear around 80mph the majority of the trip for hours on end loaded with about 500 lbs on the back. By the time I got back home, the transmission was making a definitely noticeable bearing howling noise (similar to a bad wheel bearing but not as bad). I realize I could be wrong, but my ears and gut instinct tell me it's the output bearing. The noise is directly proportional to wheel speed, not rpm. so in my mind that rules out the input bearing. and the countershaft bearings are submerged in oil so I'd be amazed if those ever failed before the input/output bearings. And yes I checked the oil level and its full and the oil seems to be in good shape (I put it in about 8 months ago).
Hypothesis: My suspicion is that the hot AZ day, with about 16 hours of nonstop high speed driving was too much for the sealed bearing, and due to the seals, it couldn't get enough oil circulation to keep it cooled and failed. I've heard of these output bearings going bad when towing heavy in 5th for long periods. As a side note, i've also towed a 5k lb trailer for 600 miles a couple months ago with this same bearing, and no issues there. But I towed at 65mph in 4th gear where the input and output shaft are directly coupled. Therefore there is (almost) no loading on the input and output bearings since the countershaft is just idling along with no real force on any gears. This time I was going alot faster and I was 5th gear, where there is both radial and thrust loading on the bearings. (especially the rear since 5th gear is right next to the rear output bearing and therefore transmits most its radial load to that bearing).
Proposed Solution: I intend to tear apart the transmission again in a couple weeks and replace the bearings again, however this time I will remove the inward facing seal from both bearings. So they can receive ample lubrication and cooling from the oil. I will not remove the outward facing seals so that I don't get excessive oil seeping out through the input and output seals. Down the line I also intend to fabricate an oil cooling system for the transmission.
As a side note: In about a month from now, the truck will do a 1500 mile trip to Texas flat towing a 2500lb jeep through a few small mountains (5,000 ft elevation change) and mostly flat ground after that. I will also install a transmission oil temp gauge before the trip to monitor oil temp throughout the trip and see if it becomes excessive as that might have also contributed to the bearing failure. Does anyone have recommended oil? as I've been using the Pennzoil synchromesh.
Truck info: Truck is single cab short bed 2wd 5.2 1500. I have an nv3500, which I rebuilt last summer since 5th was popping out under torque. Anyhow, I replaced all the bearings and seals as per the usual. The bearings which came in the kit were sealed bearings like the original ones I took out. The rebuild went well and I've put about 15k on it so far with about a 1k of towing heavy with a few steep grades, and often carrying 300-900 lbs on long drives. Aside from that, easy daily driving. The truck is bone stock including 245/75r16 ties and stock gearing. I don't drive aggressively but I sure put her to work.
Thanks for any input and experience.
Thread Starter
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Registered User
Joined: Mar 2024
Posts: 22
Likes: 4
From: Oceanside, CA
Hello,
No the seals aren't exposed to the outside directly. Both input and output bearings have a seal on either side, as well as a dedicated input and output seal on the shafts themselves. Oil would have to pass all three seals to leak out either the front or back. Or just two seals if I remove the interior ones on each bearing.
And no the oil level doesn't come up high enough to even touch the bearing. I'd just be depending on splashing to lubricate and cool. Which is going to be limited at best since the gears mostly block the face of the input and output bearings.
No the seals aren't exposed to the outside directly. Both input and output bearings have a seal on either side, as well as a dedicated input and output seal on the shafts themselves. Oil would have to pass all three seals to leak out either the front or back. Or just two seals if I remove the interior ones on each bearing.
And no the oil level doesn't come up high enough to even touch the bearing. I'd just be depending on splashing to lubricate and cool. Which is going to be limited at best since the gears mostly block the face of the input and output bearings.
Administrator
Joined: Apr 2010
Posts: 87,479
Likes: 4,223
From: Clayton MI
Hello,
No the seals aren't exposed to the outside directly. Both input and output bearings have a seal on either side, as well as a dedicated input and output seal on the shafts themselves. Oil would have to pass all three seals to leak out either the front or back. Or just two seals if I remove the interior ones on each bearing.
And no the oil level doesn't come up high enough to even touch the bearing. I'd just be depending on splashing to lubricate and cool. Which is going to be limited at best since the gears mostly block the face of the input and output bearings.
No the seals aren't exposed to the outside directly. Both input and output bearings have a seal on either side, as well as a dedicated input and output seal on the shafts themselves. Oil would have to pass all three seals to leak out either the front or back. Or just two seals if I remove the interior ones on each bearing.
And no the oil level doesn't come up high enough to even touch the bearing. I'd just be depending on splashing to lubricate and cool. Which is going to be limited at best since the gears mostly block the face of the input and output bearings.
