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TH 350 Install

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by acablik, Aug 20, 2002.

  1. acablik

    acablik Registered Member

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    I have a TH-350 in my 75 K-5 (350, TH350, 203w/part time kit, dana 44 front, 12bolt rear, 6" lift 35" tires) and it won't shift out of 1st, and there are lots of metal shards in the pan. So I bought a newly rebuild TH-350 from Advanced Auto Parts and cant decide wheter to attempt swaping them myself. I know I can do it but how much time will it take? What does it involve i.e. does the t-case have to come down? If it takes more than 4 hrs and requires special tools I may just have someone else do it. What do you think?
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well no you can do it without removing the T-Case...just got to take the engine out /forums/images/icons/smile.gif
    The shards as a blown Sprag. You could have probably got that tranny rebuilt for what the Advaced one cost including removing and installing.
    The case is ungodly heavy. Get you a peice of 3/4 ply ab out 2ft square. Get some scrap peices of 2x4. Drill a hold about dead center the ply wood. bolt it to your floor jace with a BIG thick flat washer ontop and a stack of them between your juck cradle and the ply so you can tilt it a fe degrees. put the mess under the case so the bolt is about center the case where the two halves meet. that about it's ballance point. Take the scraps of 2x4 and screw it to the ply wood to make a cradle to hold that fat pig. Once you have a jig it's not that bad. If your truck has 2 crossmembers then both will need to come out. Remove the rear one first and the skid. there should be enough room to get the cradle in there to suport the case. Remove the shift linkages.
    If you body mounts are shot the case is about touching the floor. you can lower the front crossmember down onto a jack stand to get a little more room. there is about 8 bolts that hold the case to the adaptor then you can back it up about 4 inches and it's free. If you have your carpet out it's easiest to unbolt the tranny tunnel to get at the bolts on the top as well as the bolts for the bell housing.
    Once the case it out of the way take the two cooler lines loose on the passenger side of the tranny. Disconnect the down shift cable from the carb and bracket. Dissconnect the battery. on the passengerside there is a pipe that the wires down by the starter run through. It's bolted to the belhousing with one bolts that hold it to the engine. get that mess out of the way. I'm hoping you got dual exhaust because then it wshould be out of the way. If not then your going to have to remove the Y pipe if it's wrapped around the bell housing.
    Next Jig is real easy. It's going to bolt onto the jack the same way. The bolt will center about 2 inches forward of center on the pan. take some 2x4's and put them around the lip of the tranny to keep it from slinding.
    Take the cover off the bottom of the bell housing. there are three bolts that hold the converter to the flex plate. remove them. push the coverter towards the tranny. should move a little
    Now it's just a matter of taking all the bell housing bolts off. Back the trany up about 2 inches and it's out.
    As the say in Haynes manual ...instalation is reverse.
    Your going to need a new case to adapter gasket. Southern Gear off Atlanta road sells all the paper gaskets in a package for about $8 (pepgirls gets' $40). Look under Gears in the yellow pages or Southern Gear in the white pages.
    I'll try to get you a picture of the jig for the case.
     
  3. acablik

    acablik Registered Member

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    Thanks,
    BTW, I bought the tanny for $350 from a guy who bought it at the zone and never used it. Swaping the tranies sounds like a real PITA!!! Am I right? How much should I pay to have someone else do it?
     
  4. acablik

    acablik Registered Member

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  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    $350 for a rebuilt tranny without core is a hell of a deal. It is a 4x4 model right?
    Well yeah it's a pain but if you take your time it's not so bad. Once you figure out how to suport that T-Case that's the worst of it. If you got the tools and the jack then it's about a day job in the driveway. I'll try to get that picture of the jig up today.
    Ohhh on the bolt to hodd the jig to the jack...bigger is better. that case full of fluid is about 250-300lb so don't go and try to bench press it out. I don't want to pick up the AJC and read a headline like: "Man killed but transfercase falling on head."
     
  6. acablik

    acablik Registered Member

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    No, the transmission is not a 4x4 model, I was told that all TH350's are the same except that I will have to use the tailshaft and other parts from the one that is in the truck now. Is this true? I hope so!
     
  7. Sandman

    Sandman 3/4 ton status Author

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    Then it would go on to say "Family sueing on-line help. Calls himeself the "Grim-Reaper"". HA! /forums/images/icons/smile.gif
     
  8. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    It will work, but I was under the impression that 2WD cases were weaker (not verified this yet). You will have to swap your tailshaft in ("some dissassembly/reassembly required" and "batteries are not included" /forums/images/icons/tongue.gif ) from the old unit.

    I originally had a TH350C in mine and the converter blew, replaced it with a 2WD 350 out of an old Monte (after putting a 4WD output shaft in) and the case cracked. I finally bought a truck tranny and had it gone through and pulled with it with no troubles before I swapped it out for a beefed 700 (knocking on wood as the 700 has been good so far). The other trannies may have been tired/abused when I got them, so it may have just been coincidences that they blew.

    Be careful as many cars and some light trucks received the 350C and not sure what the internal/external differences are except the 350C has a lockup converter and not considered as heavy duty of a tranny as the old reliable straight TH350.

    Hope this helps.
     
  9. four_by_ken

    four_by_ken 1/2 ton status

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    Dont forget about all the fluid. If you dont drain it first, more than likely it will go everywhere. The torque converter holds a lot also. Messy job.

    Ken H.
     
  10. Panther

    Panther 1/2 ton status

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    I could use that pic too Grim. Still planning the 350/203 swap for Sept.
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well the car 203 will bolt in but you do have to change the output shaft. That does involve taking the transmission apart and pressing the shaft out of the last drum in the case.
    My 75 is the thin case like the cars ran I do not know if it's the original tranny to the truck but I think it is. I am not sure when the thick "K" series 350 came about. I think it was 76. So far I have not had a problem.
    Here is a picture of the Jig I use when I need to remove the 203.
    http://coloradok5.com/photos/showphoto.php?photo=1043
     
  12. NITRO

    NITRO 1/2 ton status

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    too bad u arent closer. i have a th350 in great shape from a 78 3/4 that id let go for $150. $200 with 203 x-case.

    NITRO
     
  13. acablik

    acablik Registered Member

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    Thanks for all the help and the pics. I may give it a stab this weekend.
     
  14. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    yes, it will work. but you now have to tear your new TH350 all the way down to get to one of the VERY last parts in the case. then put the 4x4 output shaft in, and put it all back together.
    the guy you buy it from, did he build the trans? or just sell it to you?
    sounds like you may have gottne took... not a bad price, but you still have to have a trans(2 actually) torn down and put back together. a rebuild is the same but with new parts...

    grant
     

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