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How to replace transmission, transfer case & drive shaft?

Tiny
BLAZE45
  • MECHANIC
  • 1979 CHEVROLET TRUCK
  • 18,000 MILES
I bought this truck last night and I think that it was in 4 wheel drive ( I had no idea), and the speedometer was off by about 8 mph meaning I was doing almost 80+ instead of 70 in 4 wheel drive. Finally, the front U joint exploded ripping a huge hole in the floorboard damaging the tranny as well. I need to put in a new tranny for sure and so I am l am looking for a walk though on how to do this (removal and install).

How do I tell if the transfer case is shot? I am reluctant to buy one if I don't need it but I don't know if the U joint blew because the transfer case froze up or the U joint just couldn't handle the speeds I was pushing and shattered.

The truck is stuck in 4 wheel drive, the front tires seem to be locked in and I don't know how the actuating system works in them. I am mechanically inclined (done a few engine swaps, timing belts & head gaskets) but I have never delt with Chevy V8's or 4 wheel drives. I can provide more pictures as well. In the first picture I saw these lines, I don't know what they do?

Thanks.

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Monday, March 12th, 2012 AT 11:08 PM

7 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
I would recommend either a Chilton's or Haynes manual for this. Dropping the trans and stuff is pretty straightforward, just drain (automatic trans only), disconnect, and drop (disconnect battery, first). The transaxle is pretty much the same, except draining it first isn't as necessary.

Dropping the driveshaft is a matter of sliding under the rear and removing the 2 U-joint clamps on the differential input yoke and sliding the U-joint out of the yoke, then down and back to remove it from the trans output shaft.

You can check to see if the transfer case is frozen by turning the driveshaft.

Your vehicle is too old for our reference to have detailed step by step instructions. They'd cover 2 pages and take 30 minutes to type.
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Monday, March 12th, 2012 AT 11:30 PM
Tiny
BLAZE45
  • MECHANIC
  • 380 POSTS
I am going to dive in on Wednesday and Ill keep you posted on how it goes/ questions I may have. For the removal of the tranny/ trq. Converter on the last auto I did I had to un bolt the flywheel/flexplate via the starter hole from the trq. Converter. Will I have to do the same with this as well or can I just pull the tranny off? Thanks for your fast reply.
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Tuesday, March 13th, 2012 AT 12:49 AM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
You can just pull the transmission off once the trans to block bolts are removed, but I would remove the torque converter from the flexplate first. That helps keep messy transmission fluid off the ground. It stains, trust me. Remove the front inspection cover and use a large screwdriver to move the flexplate around to access the converter bolts.

Removing the transmission and xfer case are fairly easy. You should be able to look at them and see what needs to come off to remove them.
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Tuesday, March 13th, 2012 AT 1:05 AM
Tiny
BLAZE45
  • MECHANIC
  • 380 POSTS
Thanks for your patience, I have only ever really delt with FWD/AWD import cars and I am bit intimidated.
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Tuesday, March 13th, 2012 AT 1:09 AM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
I'm intimidated more by FWD cars than RWD cars. Too cramped and too many things to mess with. Too much hassle. I come from back in the day when there was only one front wheel drive car on the road.
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Tuesday, March 13th, 2012 AT 4:18 AM
Tiny
BLAZE45
  • MECHANIC
  • 380 POSTS
Good news! The tranny & T case came out no problem. Bad news is that I have no idea how I am going get the tranny bolted back up to the block. I used a floor jack to raise up the tranny to the engine but I couldn't get the tranny to line up to the block and come together. Any insight or help with the order of how to get things back in one piece.

Would you suggest bolting up the T case and trying to put it all in at once or just doing the tranny then the T case?

I twisted the t case and I felt a slight metal on metal contact when spinning it which is enough to make me want to get another so I don't have to do this all again. Suggestions/Insights?

The kick down cable. How important is this to get working again? Hmmmm. What else. The 4x4 levers on the T case. The levers were broken as well as the selector. Not sure what I am going to do here because without the selector hooked up I don't know what 4x4 is in Hi Lo or whatever.

There is some tranny fluid in the other transmission I am putting into the truck but about how many qrts does the TH350 hold?

Thanks!
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Sunday, March 18th, 2012 AT 4:49 AM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Lessee, We have engine. We have flexplate. Torque converter mounts to flexplate inside bellhousing. Block has two 'prongs' that guide the bellhousing onto the block properly.

The kickdown cable allows the trans to shift properly.

Your truck is too old for my reference to be able to look up exactly, but everything I've found shows trans going up, then xfer case.

Capacity is usually about 7-10 quarts.
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Sunday, March 18th, 2012 AT 5:34 AM

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