Towing with T56

[CDeeZ]

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.

I found this talking about how preload is gaining favor over endplay:
https://www.vehicleservicepros.com/v...dplay-settings

As far as the spec on setting endplay or preload as provided by Tremec I'm going to quote the guy from one of the posts I linked:

"Setting up a transmission that has tapered roller bearings with end-play/no-preload only accomplishes one thing, and that is bearing wear/noise a few years down the road when the clearences open up and there is too much play...

Great for rebuild shops and dealerships as they get more work. Sucks for the consumer... "

I couldn't agree more. It seems best to me to set up a slight preload or a very MINUSCULE endplay. Just because some engineer type at Tremec somewhere decided on that spec doesn't mean much to me. I will look at their spec and still ultimately decide what I want to do. Which if you look around on LS1tech there are hoards of people disregarding the Tremec spec in favor of tighter shimming like I mentioned.

Good point about the smaller bearing being the one to watch out for. 85MikeTPI wrote that article on building a T56 hybrid and has many posts on LS1tech pertaining specifically to the T56 which seem pretty credible to me. I'm going with the specs he used which are listed in that 3rd post I linked.... Which in the case of the counter-extension is .000 - .001 endplay.

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?

If you're talking about some of the stuff circled in red it was dust, shop rag lint etc. Also, I'm taking these pics with a new to me camera, it's on my Note 8 phone so I'm still getting used to how to operate it to depict things in the most clear manner. I'll have to revisit that when I build up that T56 for a future project. I will likely send it to Liberty to be faceplated so I'll just have them do whatever else needed at that time.

Excellent point about flat tappets. Everything I have that is flat tappets gets an extra dose of ZDDP for that reason.

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.

The hybrid T56 that is going in place of the one that was pictured a few posts back will have a fluid pump which will help the trans in any conditions be it towing, hard acceleration etc. We tig welded a -6 AN bung in the case exactly where the TR6060 has one. Eventually this will be plumbed into a pump and possibly also a cooler. I'm hoping I can control it with a TPS % or boost threshold plus a manual override toggle switch for whenever I want to have it on anyways.


Also, the specs from the Tremec service manual for endplay on the counterextension that I posted in post #57 are in contrast to this one I'm posting now. I believe this one is the correct spec (as per Tremec) but I'm ignoring them anyways hahaha. Interestingly, they both came from the same T56 service manual so there appears to be a discrepancy there. Notice the title from the service manual "Shimmin Procedures"..... Guess they couldn't be bothered to put a g on the end LOL.