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#1 |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Why did my drive shaft just fall out of the transmission?
I was driving my new 72 GMC (350, automatic, c15) at lunch and as I started off from a signal there was a loud clang and clattering and sudden loss of drive ability.
The drive shaft yoke (?) came out of the transmission and dropped on the ground. I had to get towed home. On my initial post on this forum 2 weeks ago, I had noted that I could see splines showing on the driveshaft and asked if this was normal. No one answered so I assumed it wasn't a big deal. Assuming the first pic is not normal, I was thinking the previous owner may have swapped out the transmission for a different type and then not put the correct length DS in place, or else replaced the DS with one that was the wrong length. Thoughts? I don't even know what transmission I have or how to tell. Can someone get me going in the right direction on this? My GF just wrecked her car and is borrowing my Jeep, and now my backup transportation is down. What I posted the other week: ![]() Today: ![]() |
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#2 |
Registered User
Join Date: Apr 2011
Location: Klein Texas
Posts: 3,852
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Re: Why did my drive shaft just fall out of the transmission?
I think the rear shaft is too short for your truck. Either that or your centering pins are broken on your leaf springs and the rear end is moving.
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My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe |
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#3 |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,194
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Re: Why did my drive shaft just fall out of the transmission?
I'm sorry I didn't see this earlier, but the level of spline engagement in the first pic is definitely not right.
Judging by the dings in the muffler this may not be the first time that shaft has come out and banged around. K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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#4 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,151
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Re: Why did my drive shaft just fall out of the transmission?
I remember replying to the other post that it looked like it wasn't engaged far enough, but I can't find that post anymore. Weird.
It does appear that the rear shaft is not long enough.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#5 |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
Where are these centering pins?
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#6 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,616
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Re: Why did my drive shaft just fall out of the transmission?
They're on the rear springs. It's the bolts that hold the spring togethior. They fit in holes in the spring perches (or saddles) that are welded to your rear end.
Looks to me that you have the wrong yoke and it hasn't been bolted back on. There should be a centre bolt holding the yoke to the splined shaft. |
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#7 |
Senior Member
![]() Join Date: Sep 2007
Location: Albuquerque NM
Posts: 7,848
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Re: Why did my drive shaft just fall out of the transmission?
most likely too short. take a pic of the trans pan and we can tell you what kind of tranny. is it just me or is the spline shaft sticking out of the trans too far?
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1967custom |
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#8 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,616
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Re: Why did my drive shaft just fall out of the transmission?
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#9 |
Senior Member
![]() Join Date: Sep 2007
Location: Albuquerque NM
Posts: 7,848
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Re: Why did my drive shaft just fall out of the transmission?
i didnt think so but it looked odd to me. der.....
![]() i just say it... its a longbed. yup that driveshaft is too short
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1967custom |
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#10 |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
I posted some wrong info. I'm still new to these trucks, only 2 weeks into it.
I've never had a rwd car that had TWO drive shafts before. So when I posted that the shaft fell out of my transmission it was inaccurate. There apparently is a front drive shaft that comes rearward to rest in some sort of cross member piece. What is that middle piece called? And from there a rear drive shaft meets it, and runs rearward to the differential. This is the drive shaft that fell. To me, it looks like the front drive shaft is right - it comes to that cross member piece and seems to sit where it should. The rear drive shaft appears to be newer - and the u-joints on it are new. This must have just been done recently, before I bought it. The observation above that the old muffler was dented and this may have happened before seems like it might be true. I never even thought of that. Something had ripped that old muffler from its bracket and from the tailpipe - and it very well may have been this. Anyway, the rear shaft is just a hair over 24.5" (just the shaft) or around 29" if you count the 'ears' that hold the u-joints. More pics: Front 'spline' section near whatever that cross member is called: ![]() ![]() Rear drive shaft, which fell down in the front: ![]() The front yoke (?) of the rear drive shaft, which slips over the splined part: ![]() |
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#11 |
Registered User
Join Date: Dec 2014
Location: Sedro Woolley Washington
Posts: 86
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Re: Why did my drive shaft just fall out of the transmission?
The "middle part" is called a carrier bearing. Obviously it supports the 2 piece drive shaft where they meet. The rear shaft looks way too short to me.
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72 Chevy C20 LWB-Just what I always wanted. Now, just need more time and money! |
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#12 |
Registered User
Join Date: Dec 2014
Location: Sedro Woolley Washington
Posts: 86
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Re: Why did my drive shaft just fall out of the transmission?
I'll look at mine when I get home. Is your truck a longhorn or standard 8' bed. I think the standard 8' bed rear drive shaft is shorter than the longhorn. Like maybe replaced a bad rear shaft with the wrong one. The splined section should be engaged at least half way with no load on the rear.
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72 Chevy C20 LWB-Just what I always wanted. Now, just need more time and money! |
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#13 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,188
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Re: Why did my drive shaft just fall out of the transmission?
Unless you own the tools to make a driveshaft, you are going to have to take it to a driveline shop and have them take care of it. I'd suggest towing it and having it all done there, since you don't have much experience with 2 piece shafts. Measuring and taking them just the shaft could be more costly if it's done wrong.
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#14 |
Registered User
Join Date: Dec 2012
Location: Fort Thomas, KY
Posts: 290
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Re: Why did my drive shaft just fall out of the transmission?
Just checked my GMC tailshaft and the measurement of the rear shaft at the differential from center of u-joint to u-joint going forward is 28".
The next section going forward into the front drive shaft is around 6" from center of u-joint to end of cap. BTW, it looks like your are missing your grease dust seal cap. HTH.
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#15 | |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
Quote:
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#16 |
Registered User
Join Date: Jan 2014
Location: Wasilla Alaska
Posts: 537
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Re: Why did my drive shaft just fall out of the transmission?
that's correct. So lets start at the beginning. put your wheels straight and measure center to center on each side. get someone to help so ya get pretty close.
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#17 |
Registered User
Join Date: Jan 2014
Location: Wasilla Alaska
Posts: 537
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Re: Why did my drive shaft just fall out of the transmission?
the long wheel base trucks came in 2 lengths 127 inch and 133 inch that 6 inchs looks about the distant your short?
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#18 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,151
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Re: Why did my drive shaft just fall out of the transmission?
I would almost guess that the PO had a rear u-joint failure. He went to the junkyard and got a rear driveshaft out of a 3/4 or 1 ton that is shorter and put it in. I think your rear shaft is too short.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#19 |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
Center of wheel to center of wheel is 127", which is also what is listed on my SPID.
The front shaft (runs from transmission to carrier bearing) is around 32" (shaft itself) and add another inch or so for the u-joint part, or another 6-8" for the splined part. I don't think the front shaft can be the wrong length; if it were any longer it would be too long for the carrier bearing. The carrier bearing and cross-member that holds it appear to be correct - nothing looks rigged, and it all appears to be in the original position. The rear shaft appears to be the same length as others have, based on comments above. That leaves me thinking the yoke might be the problem. Could it be a few inches too short? Connected, it only covers less than an inch of the splines of the front shaft. How long are the yokes on your trucks, if you have this setup? ![]() |
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#20 |
motor exploder
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 2,346
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Re: Why did my drive shaft just fall out of the transmission?
I wouldn't feel comfortable with anything less that 2" of engagement. You risk either the driveshaft falling out again or breaking the end off the splined part of that intermediate shaft without proper engagement. You should at least take the rear shaft, if not the whole truck to a driveline shop and tell them what is going on so they can find you the right yoke or build you a longer driveshaft. You're lucky that it didn't catch the ground and pogo your truck in the air and really tear stuff up when it fell out. You can measure and figure all you want, but the thing is too short and needs to be fixed.
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#21 |
Registered User
![]() Join Date: Apr 2015
Location: Bloomingdale, Georgia
Posts: 22
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Re: Why did my drive shaft just fall out of the transmission?
Is it possible the PO had an overdrive trans installed (say 700R4) which needs to have the drive shaft shortened (2in I believe), then before sale threw the old tranny back in it leaving the drive shaft the same?
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#22 | |
Registered User
Join Date: Apr 2012
Location: Covington, GA
Posts: 386
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Re: Why did my drive shaft just fall out of the transmission?
Quote:
I'm wondering if the truck is a Longhorn - the longer long bed. And using a regular long bed driveshaft.
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Matt Cramer 1972 Chevy C10 - 4.8 swap, long bed, and maybe one dent free body panel somewhere - SOLD 4.8 LS build thread |
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#23 | |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
Quote:
And another poster above indicated his rear shaft was also 28"-29", like mine. What DOES look non-standard is the slip yoke - mine has threading on the end which is not typical on our trucks, and appears to be shorter than standard. I just need someone who has the same length rear shaft to verify the correct length of their yoke. |
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#24 |
Registered User
Join Date: Jul 2015
Location: Dallas, TX
Posts: 167
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Re: Why did my drive shaft just fall out of the transmission?
Can anyone with the 127" wheel base get me a measurement on their slip yoke (think that's what it is called)?
Last edited by centuryhouse; 07-30-2015 at 11:44 AM. |
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#25 |
72 GMC
Join Date: Feb 2008
Location: Wells, Maine
Posts: 534
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Re: Why did my drive shaft just fall out of the transmission?
I have a mostly stock 1972 GMC 1/2 ton 127" with a 350 / TH350.
I just went out to the barn an took a quick measurement. Weld to weld on my front shaft is about 24". My tranny tail is about 6". I was having trouble because this thing is not up in the air. I couldn't get to the "yoke" w/ splines which slides into the tranny. If no one chimes in, I can measure whatever you want on the weekend - - - if you remind me !
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