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Blown 700r4, time for a th350/205?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ryan88Jimmy, Jun 16, 2000.

  1. Ryan88Jimmy

    Ryan88Jimmy Registered Member

    Feb 17, 2000
    Likes Received:
    Winnipeg, Manitoba, Canada
    Well my 700r4 finally finished itself off, and a couple of the shops I've talked to in town have given me a round figure of around $1500 canadian to rebuild it, also the 208 is already making some kind humming noise, (probably becaue when I first bought it it had gear lube in it) so it will probably need some work soon also. My question is, would it be more worth my time to replace the 700r4/208 combo in my 88 jimmy with a rebuilt 350/205 combo.

    What kind of other costs are we talking about when doing a swap? I realize I would have to replace the drive shafts, but what other misc costs would there be? There shouldn't be any problem mounting the th350 to the engine, but I'm not sure about differing lengths of the 350/205 combo. Would I have to drill new holes for the tcase support? Any info would be greatly appreciated

  2. J.R.

    J.R. Guest

    hey ryan,i replaced my 700r4 with a t400 and used the factory np208 transfer case.i spent about $1000 on the swap.it really depends what you use your k5 for.if it is your daily driver i would stay with a 4sp auto.one thing to remember is your factory diffrentials are geard for the 4spd auto.so when you change to a t350 or t400 you really should regear your diffs. also.there are places that can build a very strong 700r4,for around $1200 u.s.,witch ever way you go,good luck with it!!!

  3. BigBadBowTie

    BigBadBowTie 1/2 ton status

    Apr 6, 2000
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    I got 125,000 out of my original 700R-4. I've got 50,000 on the Brand New GM replacement. I love these trannys. A properly built one will last forever. I would have purchased a Premier Performance T700 but I was in Germany when the original, blew & the logisitcs of it were mind-boggling. Here are a few web sites. I think you'll be kicking yourself if you give up that 30% overdirve. I love cruising the freeway @ 75mph with 4.11:1 gears & 35" tires at 200rpm's.



    86 K-5
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

    Feb 24, 2000
    Likes Received:
    I personally really like the 700r4's. They have a much lower 1st gear than the 350's for better acceleration, plus the overdrive makes highway cruising nice.
    The newer 700's, or the updates the shop should do if you have an older (pre'87) truck, makes these very reliable and should last just as long as a 350. The biggest factor for automatic transmission life is keeping them cool. Another thing to make sure of when replacing the transmission is to flush out the cooler lines and use a new converter.
  5. HarryH3

    HarryH3 1 ton status Author

    May 31, 2000
    Likes Received:
    Georgetown, TX
    I like the 700R4. You get a lower first gear plus you get overdrive. The high failure rate of the early 700R4's gave them a bad reputation. GM did a major upgrade for the '87 model year and the newer ones hold up much better.

    The one in my '87 K5 still worked great when I traded it off at 125K miles. I drove that poor thing so hard that the hard-facing came off of the side gears and toasted the rear end. The tranny never complained.

    The one in the '91 S-Jimmy is still going strong at 116K. I expect it to last forever behind the 4.3L V6. Oh yeah, the fluid has never been changed in it. It still has the stuff in it that it left the factory with. [​IMG]

    The one in the '94 Suburban has 87K or so on it. No problems to date. That is one heavy truck!

    I've got a Turbo 400 in the ThunderTruck(tm), but there's a 700R4 sitting in the garage that came out of the same 'vette that donated the engine. Someday it will probably find its way under the truck. I just need to change the output shaft to either match up to my NP205 or I may go to an NP208 to get the better low range gearing.

    <font color=black>HarryH3 - '75 K5</font color=black>
  6. CrazeeBush

    CrazeeBush 1/2 ton status

    Apr 17, 2000
    Likes Received:
    Middle Tennessee
    Mine has the original 700R4 and I'm @ 150,000 and it's just now starting to show some age. I hope I can get another couple of years out of it. =) BTW, it's an '83 and the only time it's had a fluid/filter chnge is when I first got a hold of it 2 years ago.

  7. 4x4blazer

    4x4blazer 1/2 ton status

    Jun 14, 2000
    Likes Received:
    My '84 chewed up 3 700R4's before I finally gave up. I now have a turbo 400 with my old np208. I have never been happier. But I have to admit that I do miss overdrive sometimes ( especially while I'm watching the gas meter ). It cost me about the same for the swap as another rebuild on the 700 would have been. The only extra expenses where for a little refabrication of the crossmember, a different tail yoke, and a 700 to 400 swap kit( dip stick and stuff). But I think it was werth it.

    Whichever you descide, good luck.

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