Towing with T56

[CDeeZ]

All good bearing manufacturers publish this fact in their failure analysis documents.

The factory (Tremec) endplay specs for the T56 is .000" to .002" endplay on the mainshaft, .000" to .002" preload on the countershaft, and .000" to .002" endplay on the countershaft extension.

And this is to both of those statements listed above..... And?????? So what???????? Don't take this personal and go ape shit again I'm just saying. I do what works for me. I don't care much about what is written down somewhere or stated. I will investigate it, consider, and ultimately it is still MY decision to make. So what's wrong with having some autonomy in the matter and doing something independent of what is stated or published by someone else? ALL OF THESE QUESTIONS ARE RHETORICAL. Don't freak out.

[CDeeZ]

I found this and thought it an interesting read.

It is a failure analysis from SKF. These are excerpts from the "Limits of acceptability"

Abrasive wear:
"Wear that results in a mirror finish on the bearing components might be acceptable. However, further clean conditions are needed. When wear causes ridges that can be felt with a fingernail or other blunt probes in the running surfaces of the bearing, the bearing should be scrapped."

Corrosion:
"Bearing components with corrosion damage that can be felt with a finger nail should be scrapped. A stain on the surface of the bearing components might be acceptable if it can be removed by polishing with fine abrasive paper."

Vibration corrosion:
" If the damage to the surfaces can be felt with a fingernail, then the bearing should be scrapped. Light vibration markings on the bearing surface might be acceptable if they can be polished away with abrasive paper and/or cannot be felt by a fingernail."

Indentation from debris:
"Over rolled indentation damage is not acceptable if widespread throughout the bearing as shown in the photo. It might be acceptable if only slightly damaged and not present across the entire raceway."

Discoloration:
"Lubrication stains might be acceptable if no other damage is present. Blue discolouration caused by heat is not acceptable on any bearing component."


I think this is interesting. I have never looked into any of this before but I have always used my fingernail to see if it catches on bushings, bearing races etc. as a determinant of whether the part in question needed to be replaced or not. It seems that SKF is reliant on the user of a bearing being smart and independent enough to be able to make a judgement call in the field. This was my approach. The bearing staining that I have witnessed in that other T56 from the pictures had a rusty brown/dark red discoloration. Which, according to this SKF failure analysis document, is "acceptable" provided no other damage is apparent.

[lionelhutz]

SKF really only says it might be OK, which is likely why you quoted acceptable. If you read what I posted, I said the bearing has staining which is the first stage indicating it has experienced overheating and also that means it was taken close to having permanent damage. If it was overheating, then when the overheating continued it would have advanced beyond the first stage. It might be still be Ok, or it might not. If it was a big bearing for a critical application that cost a good chunk of cash then a much closer inspection would be called for. On a cheap bearing, it makes sense simply to replace it and not take the chance on it. It's easy to determine when a bearing is definitely bad, but not always so easy on a worn one that has bad indicator signs but still doesn't show failure damage.

[CDeeZ]

Yeah. It just seems to me that they want the end user to have sense enough to know what they're dealing with more than anything. They're not saying Yes or No one way or another but just "might be acceptable". Which I still take to mean that the end user of the bearing is responsible for being smart enough to make a judgment call. I agree; if there was any doubt just replace it on a cheap bearing. But again, it all comes down to a personal judgement call, for me anyways. Can you post the failure analysis documents indicating bearing staining is a first stage indicating overheating? If so, that will be an interesting contrast to the SKF document as well as the Timken video I posted.

Maybe I have been lucky, but I can't recall a single time I have ever had a tapered roller bearing fail on anything I've ever messed with that uses them. I had a T56 pilot needle bearing explode and wreck an LTx T56 input shaft. I have ONLY run pilot bushings after that. And bronze ones.... I check them with a magnet to be sure they're not iron bushings, that's no bueno for a pilot bushing.

Do you care to weigh in on preloading the bearings a tad bit as opposed to having endplay like I mentioned a ways up? I have found multitudinous posts on LS1Tech where guys are setting them up with preload. Which is directly contrary to what Tremec publishes.... Here are some I found easily.

https://ls1tech.com/forums/manual-tr...d-setting.html

https://ls1tech.com/forums/manual-tr...ntershaft.html

https://ls1tech.com/forums/manual-tr...-shimming.html

[lionelhutz]

They always leave it up to the end user. The right wording makes it easier to not get sued.

I don't recall which manufacturer so I'd have to look for it. I've also seen it in online and print documents in industry magazines before.

From what I've seen, taper bearings tend to have a decent life with a fairly wide range of end play, have best life with a little preload and then die quickly with too much preload. In other words, the life of the bearing is the best with a little preload and the life drops off slowly as you move towards too much endplay while it drops off quickly with too much preload.

You can find papers where trucking companies are starting to use specialized equipment to install axle bearings with a preload. It's interesting stuff but basically comes down to them being more reliable when done with precision as opposed to putting the nut tight and then backing it off a little.

I have no idea why the specification is how it is. There are probably good reasons behind it. 0.001" to 0.002" seems like a decent preload target for the sizes of bearing in the transmission. The only reason I could see it not working is if the shaft heats up more than the case and tightens them further, which might be possible on some of the OD gear sets while under significant load. That one bearing is the smallest so it would be the one to watch for issues due to too much preload.

[Xnke]

What's worse, CdeeZ, isn't the bearing staining, it's the surface shear failure in that same photo. Look on the gear teeth at 8 and 9 o'clock, you see those tiny pits on the involute face? That is the material failure. They will only get worse, and there's nothing you can do to fix them. Maybe it's just dirt, but to me, that's the textbook pitting of a surface shear failure.

Same thing happens in a flat tappet cam when you don't have enough EP lube in the oil, or the valve spring pressure is too high, or you're just running much too aggressive a profile on the cam lobe. The lube gets forced out and you get metal-on-metal right there in a tightly focused area, which results in the hard surface literally tearing off the softer core-thus "surface shear" failure. Ways to fix that issue is use a lube with more phosphorus or sulfur, although I think boron compounds are the new hotness in EP additives.

Could also be that the oil was fine, but just breaking down from the same heat that stained those bearing rollers. Do you have more photos of similar detail on the countershaft gears?

[1project2many]

What's worse, CdeeZ, isn't the bearing staining, it's the surface shear failure in that same photo. Look on the gear teeth at 8 and 9 o'clock, you see those tiny pits on the involute face? That is the material failure. They will only get worse, and there's nothing you can do to fix them. Maybe it's just dirt, but to me, that's the textbook pitting of a surface shear failure.

I noticed the same issue. But without knowing the condition of the transmission before installation I didn't want to assume all of the damage was due to towing. If the damage is due to the current application, it seems like the transmission has survived long enough to suggest that it may be worth investing time to improve it's chances.