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TH350 and Torque converter advice needed.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by laketex, Jul 8, 2000.

  1. laketex

    laketex 3/4 ton status

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    I'm about to pull my TH350 tranny and have a couple questions on my rebuild. What I actually did was burn up the torque converter and drop fluid levels in my transmission. What do I need to concentrate on in this rebuild? And is there anything I should beef up over stock? I plan on adding a mild shift kit, should I get a HD sprag? I'll be having a shop do the rebuild, I'll pull and install. I also will be needing a torque converter. My truck is mainly trail only with a little driving around town. It has a stock 350 engine for now, may do a mild rebuild in the future, a 203 case, 36" swampers, 4.11 gears, and a detroit rear. Thanks for any help you may give.

    [​IMG][​IMG]
    Durant, Ok
    '79 Blazer in progress
     
  2. Donovan

    Donovan 1/2 ton status

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    You probably don't need the HD sprag in it. I have not seen the need to do that until you get a lot of horsepower and torque thru the TH350. I run a Caddy 500 behind a rebuilt TH350 and it is holding just fine. I would get a Trans-Go shift kit. They seem to be the best and they are even better than B and M, which I thought was go until a couple months ago when we found the Trans-Go and they will do more for you. Look for a low stall convertor for what you want to do. Also look for the Torque Multiplication of the convertor. Some companies will have the spec and some will not have a clue what you are talking about. Look for a company that knows what it is and they can tell you what you are getting. The Torque Multiplication is how much the convertor multiples the engines torque. Say your engine puts out 400ftlbs of torque you multiples it be the T/M factor which is 1.8 and will get 720ftslbs of torque. Now say the T/M factor is higher like in an Allison convertor which some are around 2.8 you will get 1120ftslbs of torque. That is just by getting the right convertor. So ask the companies a lot of questions about that. I know Art Carr has done a lot with the T/M but they are pricey.

    Donovan
     
  3. Waxer

    Waxer 1/2 ton status Author

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    Another thing to look at is having upgraded clutches put in it. I had them put in mine 2 years ago and its still workin its ass off for me.
     
  4. laketex

    laketex 3/4 ton status

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    Thanks guys, I bought a book and I think I'll do a few little tricks as well as tougher than stock clutches. Also studying torque converters. That T/M factor is interesting, perhaps I can get quite a bit more oomph through the entire truck. Back to the books...

    [​IMG][​IMG]
    Durant, Ok
    '79 Blazer in progress
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    THE VERY BEST THING TO DO TO ANY AUTO IS A BIG COOLER. Heat is was roached your old converter. Now if you live in a area that has a pretty good cold season there is a concern of over cooling the tranny. It does need som heat for proper lubrication. Jegs and Summit sell a thermastatic valve that will keep the temp regulated and for a cold climate I would recomend using one.
    Now one guy said don't see the need to beef the sprag with stock engine...I feel differently about that My truck has a tired old 350 in it and the sprag failed and ate up some partsIncluding for foward drum and some other damage. I would say a beefed sprag will never hurt and really all a beefed sprag is in most cases is doubled up springs to keep plenty of pressure on the rollers. That said I didn't know and was in a hurry when I rebuilt my tranny and didn't beef it. I agree 100% with the rest. it's right on the money.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     
  6. Donovan

    Donovan 1/2 ton status

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    The reason I say I would not get the heavy duty spray is because they are $300-400 for the unit. I don't think you can't just put a 34 element sprag in they have to modify a TH400 unit to go into the TH350. Also there is a thing called a case saver that go in the bottom of the case because they wear the case out. I can't explain it but the tranny shop will let you know if it is needed. Just to let you know they could be a problem with the case. The case saver cost only I believe $60 for the a good one.
    I just reread Grim-Reaper post and I believe they do have a Heavier Duty stock sprag unit I was only thinking of the 34 element unit that cost alot more. I would look into it anyways.

    Donovan
     
  7. Jeff427

    Jeff427 1/2 ton status

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    I put a TCI towing converter in a TH350 in a 3/4 ton truck along with a TransGo shift kit and added a tranny cooler when I rebuilt the tranny. And it has held up great! After I did the mods the truck got better gas mileage, and would pull another vehicle at an idle. In the book <font color=red>Turbo Hydra-Matic 350 Handbook</font color=red>,(this book is awesome, nobody building a TH350 should be without it.) Ron Sessions states that high performance clutches do more harm than good in off-road use, because if they get starved for oil (while rock climbing), they will burn the steels. The stock style clutches use a type of paper friction material that actually absorbs a certain amount of oil (tranny fluid), so if the clutches are starved, the oil soaked into the friction material will help prevent the steels from burning.
    Just a little something to think about.

    Jeff427
    <font color=red>Mud Dog Off Road Club</font color=red>
    http://muddogoffroad.coloradok5.com
     

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