My GMC, a little update

Quit busting my beans Nattie, I am hoping to upgrade to a concrete work area someday.

The weather is finally down to around 103 or less during the day. Man it's been a long summer. Global warming my butt. The sun causes global warming. I have a hard time believing that since the day man discovered fire we have somehow managed to put more junk in the air than all the volcanos that have spewed trillions of pounds of sulfer and other junk over the past couple million years.

I ordered my biscuits on friday.
Amazon.com: Trans-Dapt 9314 Biscuit Motor Mount Pads - Set of 2: Automotive

Transmission is clean and degreased. Have yet to throw the new pump seals on.
Lastly, the motor with all it's goodies. I just need my adapter plate and starter then I can get the new drivetrain in.

What is WMO?

Waste Motor Oil I believe.

Yes WMO Waist (used) motor oil. Not to be convused with a MWO which is Modification Work Order.

That is a purrdy motor you got there. Looks like it should hook up 1.2.3. with out to much issues.

Well, crap. Can anybody take a guess and point out what the problem will be with this Th400 output shaft? No slip yolk. Will this be a problem for my street use or should I just not worry about it? I suppose if there was any give in the system the trans mount would provide some flexing.

It looks like the yoke slides inside the transmission like on a 2 wheel drive pickup? Won't it just slide out? Sometimes if they get pushed in too far they stick in. How about a close up pic?

Yep, I think the slip yoke slides inside the tapered tailshaft housing of that transmission. It may just be seized on the splined shaft. Looks like it is bottomed out. You may have to pull on the yoke and tap (toward the rear) quite firmly with a heavy hammer.

Gunfreak25 said:

Quit busting my beans Nattie, I am hoping to upgrade to a concrete work area someday.

The weather is finally down to around 103 or less during the day. Man it's been a long summer. Global warming my butt. The sun causes global warming. I have a hard time believing that since the day man discovered fire we have somehow managed to put more junk in the air than all the volcanos that have spewed trillions of pounds of sulfer and other junk over the past couple million years.

I ordered my biscuits on friday.
Amazon.com: Trans-Dapt 9314 Biscuit Motor Mount Pads - Set of 2: Automotive

Transmission is clean and degreased. Have yet to throw the new pump seals on.
Lastly, the motor with all it's goodies. I just need my adapter plate and starter then I can get the new drivetrain in.

Click to expand...

Your motor appears to be defective... where are the obligatory valve cover & oil pan gasket leaks?



'Tanner'

I'm lookin at those headers and I'm seein an easy turbo upgrade with there shape and size

Holy crap, I think you may be right henderson......all of the "slip yolk" output shafts that are for sale for Th400's look just like mine. I think it has indeed frozen itself in place and with some work it should slide out.

Thanks a lot for the tip Henderson. The yolk was indeed seized onto the output shaft. I picked it up by the yolk on the crane and a few taps with a mallet broke it loose, it slid right out.

I am not sure just yet what caused the yolk to seize up. But here's my findings so far. With the tailhousing removed, the yolk will slip onto the output shaft a full half inch further than with the tailhousing in place.

Which tells me the problem is in the tailhousing. Is it possible the bushing in the tailhousing is too small causing the yolk to get stuck if/when pushed in too far?

Saw a guy chain the yoke to the vehicle and put the transmission on a 4 wheel cart. He pushed the transmission really fast and when it came to the end of the chain the yoke popped out. It helped the driveway was sloped and had new concrete. Unfortunately the transmission continued on and slammed into my receiver hitch breaking the bellhousing. True story.

1. The play is what I've seen many times in TH400 and th350s. I think the yoke needs to be in there when you measure the play. The yoke rides on the tailshaft bushing and supports the tailshaft of the trans. I would not worry about it. I have seen many with a lot of play WITH the yoke in. They did leak some.

2. I don't think so. When I first saw the pics I thought the yoke was too far in. I assumed you pushed it in so it would not fall out. I have had first hand experience with bottoming the things out resulting in many broken tailshaft housings before I figured it out. -Custom driveshaft, lifted vehicle, too steep of an angle, big jump, hard landing, impressed friends etc.I would consider shortening the driveshaft if you have to.

If you have to shorten the driveshaft take it out of the transfer case end. Remember you will never exceed 58 miles an hour.
The transfer case has a real (and big) bearing in the front that is supported by real iron. The transmission has a tailshaft bushing inside an aluminum housing. A machinist who used to rebuild me driveshafts showed me how to do it a few years ago. I think he fet sorry for me. Mark the entire length tube and yoke position with a file first. He told me to cut the driveshaft at the rear to the desired length. This way I can see how thick the tube is. Wrap a piece if paper around the driveshaft where you want to cut and paint it. It gave me a perfectly perpindicular line to cut on. It is important to be square when reinstalling the yoke.I ground the weld off the rear yoke. I understood why he wanted me to cut first because I could see how deep to grind. place the rear yoke back on, align your file mark and tack in 4 places to prevent warp. Recheck for square and weld. He felt ballancing was not necessary if you do a good job. we were running pulling trucks, mud boggers, and toys not 120 mph racecars, or vehicles made to run freeways for 10 years. He felt the diameter was small enough ballance was not necessary. I guess we did about 30 for ourselves and other friends. We never had a driveshaft problem. I know some people will balk at this, just an idea, you decide for yourself.

That yoke was intended to slid in and out over every bump, when you loaded groceries in the trunk, at drive in movies...

Can you move the engine forward 1"or 2"?

You are correct again Henderson, end play is measured with the yolk in place and the extension housing bolted on. In which case, mine has zero play.

Funny you mentioned moving the engine forward to account for the now longer driveshaft. I was going to say, all that I would have to do is plug and redrill the hole in the crossmember for the rubber trans mount. You think a half inch would be sufficient? That should leave plenty of room for the yolk to slide in and out some. Perhaps a full inch?

I'd try to get enough room so you can take it out if you need to. I'd want at least 1/2 to prevent pressure on the transmission, but that is only my opinion. I'd aim for 1" if you have the room.

An inch is no problem. As soon as I get my adapter plate I may even drop the drivetrain in to start finding any potential clearances issues before setting too many things in stone. My main concerns are the headers and the horizontal oil filter. Though the latter is easily fixed with a vertical or remote filter. The right header points straight back at the firewall. I was told it nearly hits the large cast iron mount on the frame that connects the uppermost torque rod. I can carve a little on this if need be, or I can chop the end of the HMMWV header flange and weld on a 90 degree pipe to bring the flange down lower. Same concern for the left (drivers) header. The HMMWV headers do NOT hug the block like traditional headers do.

Worst comes to worst i'll be using a different oil filter adapter and trading my headers for civi ones. Other than all this, I know the 6.2 will fit very nicely.

I can't wait to see the progress.