In all my studying up to do a rebuild on one of these for a fellow that is pretty low on funds, I have found very little info about the lube system.
I'm just wondering how well that input to output seal works? It sure seems iffy plugging it into splines and being very low on rigidity.
So what sort of pressures are running in that circuit?
A video of a THM 350 showed it used a plastic bushing in that area, that the fellow replaced with a bushing. Would this be a good thing to do on a 4L60? I would think the added support would be a good thing.
Machining out the splines and making a plug to hold said bushing is what I was thinking?

 

One other thing I have not found. It seems there is plenty of info on changing bushings during a rebuild, but zero information on the actual bearing clearances, I guess its a machinist thing to want to know that. The last transmission I built was REOF09A Jatco, and if I remember correctly, those bushing clearances even with new bushings were a bit on the large size. Its been so long now since working on other transmissions I don't remember their clearances, I've not seen them in manuals, but then I'm too lazy to dig into some of them.
Is that normal for transmissions to have a bit larger tolerances than standard of say .001 for every inch of journal or shaft diameter?

 

The rubber teflon seal works well . The plastic one was early style 700r4. They will work in a tight squeeze but were known to crack up break over time.
Someone did at one time make a BRASS one. Nice little piece and I liked the IDEA of additional support stabilization. But they stopped , Likely because of the hasel an expense of making them, I managed to make one and it is in a trans functional , I did this by cutting down a piece of brass stock to just a little larger than the spines in the drum . cutting to correct height. Then used a cut out of that section of the drum. Heated the brass to far from liquid but more permeable state and then used press to push it into the drum part. Then let it cool. Tapped it back out. cleaned up with air grinder and spinning wire brush then put back in lathe and drilled center hole to just a bit smaller than shaft (could not find a direct bit size ) then use small brake hone to size it. But took better part of a day to make one. Though I imagine with the right tooling could be done much quicker. But what I mostly determined was with the cost of brass stock that size. That alone made it more than anyone would pay for one i had 15 dollars in just that little bit of brass. Not to mention the time and labor .

 

Clearance on bushings . I like them semo snug with no drag and never loose. But the option we have are pretty must as the come when you buy them and whatever they come too. I generally just replace all . Then go by feel. One I am not to quick to replace is the big one in the 4l80e center support as on few occasion then new one was actually looser fitting than the original. So replacing it i do as a judgement call.
Though I am aware everything has some exact measurement it should be, I think for many of not most experienced builders it is about feel in many cases.

 

Last one I did it had that deal with the old bushing fitting tighter than the new one. Very discouraging, makes it a waste of time changing it. I wonder how well making your own bushings in that situation would work say using 660 Bronze? Likely not enough strength with a thin wall and no steel backing, it would probably loosen up and fall out?

 

Probably so and yes discouraging, This is why If I find I have a nice looking bushing in the unit and it still fits well , I will just leave it, Sadly increasingly this is not the case as these units are getting so old

 

The bushing if I remember correctly was about 5/8 ID, and calculated clearance was .003, before install of the new one it was a bit bigger, I thought well it should shrink when installed in the hole, nope not much it was about .0005 larger than the old one installed.
I've never seen a video of any transmission builder checking the bushing clearances, they all seem to slam bam and go for it.

 

A thin strip of scotch tape is what I use in some cases. !/4 wide situated vertically on the ride surface. Slide parts together and see if the bushing can peal off the tape. If so or partially so with no drag equals my good to go standard. I may be wrong.

 

On this I generally and people HATE hearing this go by "FEEL" I want the part to have little if any side motion and 0 drag at the same time .
I used to years ago have a large collection of bushing from many different trans i had collected over the years and i remember sometimes i would intentionally use a bushing meant for something else here and there because maybe it was wider or perhaps same outside diameter but a bit small on inside, I liked that because i could use a brake hone to get a very precise fit .
I am sure they is a method to measure all of this though I doubt many if any do except maybe an engineer . For the most part when it comes to bushings it visual and feels like judgement call.
But as Bob mentioned It is frustrating and more and more common of late to replace a bushing because it felt a little loose only to find the new one is worse.
I think a lot of that is like a friend of mine at a machine shop they do comercial stuff but have over the last few year seen much that used to be done in china shift here and well they are not really set up for it yet and it's a learning curve tooling and setting up for things they have in the past not done.
Also OFF SUBJECT but I recently accidentally bought a chinese knockoff of the sonnax the sonnax servo (i mean it did say sonnax in the title) but I didn't pay attention to the price "way lower by about half" but I was curious and took it apart and compared to the sonnax and my finding was well lets say surprising. While I cannot speak to strength which is why I'm holding off till I do some test with press etc . Appearance wise outside it was identical, In fact if not for the chinese writing all over the box I would have never known. But inside was a surprise, the servos themselves were thicker aluminum and appeared to be much beefer than the sonnax . Particularly the larger servo which was about 2x thicker i have always though the sonnax seemed awfully thin where the washer rides and have seen a few crack there over the years.
However the immediate down sides noted were the washer was not grade 8 and I guess to compensate for the thicker servo was thinner. That would need to be addressed with a grade 8 or 10 washer if available and the seals they use are wrong , Not dimensionally but material wise. They didnt "feel" right to me so I placed one in trans fluid and it swelled overnight significantly.
Anyway more on that when i have time to play with it more. I did however send an email with link to it on amazon to sonnax and let them know they were using the sonnax name and part number in title and description.
Just something of note, beware when ordering stuff, But still interesting findings thus far.

 

That's why I don't buy parts from Amazon, you never know if you are ordering the OG part or a knock off.

 

True but at least part of my point is in this case at least appearance wise ill tell more after a few test , Well it seems to be a better made piece is all .