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6L50 transmission repair

Blue85

Blue85

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Anybody know where to get the book for one of these? ATSG (and some others) publish a manual for 6L80/90, but there seems to be nothing for the 6L45/50. I'm assuming that the '80 book will be better than no book at all. So is the reason it's not available that it's so similar, or that GM doesn't want anybody working on them?
 
I’m surprised ATSG don’t have a guide for that trans. I’m going off memory here but I can’t say the ‘80 is the same as the 45/50 version. Wiki calls them similar but the ratios do differ.

Though part of the reason I don’t recall how similar they are is we never really tore a 45/50 version apart. If they shelled they did so in such a way it was cheaper to replace than the cost of all the parts and added labor to rebuild.

Sadly the way the prices were on individual parts and components it wasn’t hard to exceed the replacement price with labor.
 
Apparently they use the same case and valve body, but get different planetary gears and bellhousings. The clutch packs must be bigger in a '90 than a '45, and presumably some other things like that. The exploded views in catalogs claim to apply to all 4 versions. As you know, it can be the little details that make the manual important, like which way up a snap ring goes.

This trans has been working fine, but the output shaft splines have corroded away, as was a known common issue with CTS. That part is $100 and simple to change once the transmission is pulled and almost fully disassembled. The transfer case input shaft also needs to be replaced. Dropping the car at a driveline shop would cost more than the car is worth, so my son will do most of the under-car work and I'll do a lot of the bench work. We're moving to the 2010+ style parts that seal the splines with an O-ring just because it's the same money. The older style, if new, would last as long as this car will be on the road.

I was joking we would pack the splines with JB weld, throw the case back in, get a for sale sign and hope it holds for a test drive :whistle:
 
Transfer case is just about back together. Clutch pack looks good, chain doesn't have much slack and input/output bearings look good.

The output/input shafts are the newer style, so somebody has fixed this before and even with the o-ring, the splines still rusted away. It's possible both units are just salvage yard pulls and still have over 200,000 miles. Hard to tell at this point, but if the transmission is in as good of shape as the T-case, we won't need many parts.
 
I've done a few of those for the splines stripping out. I don't recall any real difference between the 6l50 and the 6l80. Just a little bit smaller parts
 
The fluid is definitely burnt, but nothing incriminating in the pan. Torque converter looks freshly painted and little sign of wear. Like I said, someone has been in here before, so we really don't know what we're dealing with.

20220823_200654.jpg

Notice the little chimney on the plug pan to the right. Apparently that is the fill level indicator. Since they deleted the dipstick and replaced it with a little plug and there are exhaust pipes and heat shields on both sides of the pan, you have to have the car running, warm, raised off the ground but level, pull the plug and then pump fluid up into it until some drips out. Yay!

20220823_200658.jpg
 
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I can't believe how easy this is since we're not taking every assembly apart. Plus the design is mostly o-ringed with no custom paper gaskets (because we're not taking the valve body apart.) Even with the large PITA snap rings, I swapped the output assembly to the new shaft in like 10 minutes. So far the only new part is the output seal.

20220824_175629.jpg
 
This is my first 6-speed. Before I've only done 700R-4, a 4L60e and a couple 4T65e.
 
Anybody following along who has done one of these before has been waiting for me to get to the hard part, right?20220824_193111.jpg20220824_193035.jpg
 
Any suggestions for what to put on the splines? I was thinking anti-seize.
 
That would work, and should stay put better than a grease. Plus, you will earn the curses of the next guy that takes it apart and can't get that stuff off his hands, clothes tools, etc. etc.
 
Thanks for dropping in on my thread @Greg Ducato. I always try to leave things in good shape for the next guy, because the next guy is usually me.
 
For the record, the 6L80 book has been just fine. Maybe if I was taking apart the clutches some differences would show up, but probably nothing that careful notes on disassembly wouldn't solve.
 
What we figured out years ago for PTO mounted hydraulic pumps on heavy wreckers was to mix anti-seize with grease to make the pump and PTO splines last the longest. We would drop the pumps off annually to lube them, as a hydraulic wrecker with the stabilizers down, boom out and up, was the worst time to have a failure when you were pulling hard.
Just my experience.
 
Greg Ducato said:
Kudos for the improvised snap ring tool, that is some genius level improvisation right there and yet the most dangerous snap ring pliers ever conceived.
Click to expand...
That's just how I do these things. Don't worry, those shrub cutters are too dull to put my life in danger. I do this so seldom, the only way to know what's really needed is to tear into it. I can't find it now, but years ago I posted on a GTP forum about all the workarounds I did to rebuild a 4T65 without any special tools. I thought I was being helpful, but it was a mistake. A few guys gave props for innovation, but mostly they all flamed me for being a hack and how the transmission could never last if I hadn't used the official clutch spring compressor or whatever. Making the tools is way slower (could lose half a day!), but as long as it's assembled as it should be it will work as it should. I did finally go back and update that thread years later when I sold the car, trans still working perfectly like 50,000 miles later.

EDIT: Oh yeah, they were sure the "quality" of the build was simply the amount of aftermarket parts you threw in.
 
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The dipstick replacement plug is nearly inaccessible with the exhaust in place, so we tried disconnecting the cooler lines and filling from there. This didn't work, but the idea was to add over a gallon before installation and then top it off after installation. We settled on the plan of overfilling, then warm the car up, pull the fill/check plug and let it down to correct level.

This seems to have worked, as the car is driving. Filling it from the cooler lines at the transmission didn't work (fluid just spilled back), so we pulled the upper cooler line from the radiator and filled there. After the recommended rebuild level had been pushed in, the car was raised, running, the fill plug pulled and after a bit some fluid dripped out, so level is probably close.
 
I'm told there is an aftermarket dipstick kit available, but big $. It would be interesting to see if a truck tube and stick could be reworked, but it's probably not going to happen on this car. Hope it works, he's supposed to move soon.
 
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