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tranny dilemma

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 76GMCJimmyinAZ, Jul 18, 2000.

  1. 76GMCJimmyinAZ

    76GMCJimmyinAZ Registered Member

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    Okay, here goes. Love my truck- it's a long-term keeper. Rebuilt my T350 a couple years ago, but it appears to have a leak requiring removal to repair (not real anxious to attempt that on my own, so several hundred $$$ labor). I have always regretted not having my xfer case rebuilt when it was out for tranny ohaul. Sooo, I have been wanting a 700R4 for some time, and I'm thinking now is the sensible time to do it. Is the R4 a good idea? I've seen several conversations on here about it... What xfer case goes with the R4? Any particular year runs of R4's to avoid? What mods should I have done to the tranny? I tow occasionally and it's hotter than heck where I live. I'm thinking the conversion will cost me approx $1,500. That reasonable? How intense is the conversion? Better mpg?

    I have about a hundred other questions... =)

    GUZZLES GAS BUT IT'S FREE AND CLEAR!!!
     
  2. MICHIGAN BLAZER

    MICHIGAN BLAZER 1/2 ton status

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    You'll definately get better mpg...you got a 4th gear. You should be able to buy adaptors for just about any application. I loovve my 700r...wouldn't trade it for nothin'....well until it's broke at least!

    <font color=red>MICHIGAN BLAZER
    <font color=green>89 Fullsize Blazer
    87 Cherokee
    65 IH Scout
     
  3. JimmyDie6.2

    JimmyDie6.2 1/2 ton status

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    pre-87 700s are weak. avoid them unless it was rebuilt with stronger parts. yes better mileage, but make sure you are geared for it if you have 3.08s or lower I wouldn't recommend it. and the T-cases are different between the 350 trans and the 700. JS
     
  4. Blazer1970

    Blazer1970 1/2 ton status

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    What size tires, and what rear gear ratio do you have? The 700R4 has a .7:1 OD, and you want to have low rear end gears to get any use out of the OD. My Sub has 3.42s and 33" tires, and I do not drive it in OD except over 70 on the highway. I get better mileage, and way better driveability in drive. I think 4.56s with 33s would be good with a 700R4 (maybe 4.10).

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  5. turbo

    turbo 1/2 ton status

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    First a 4x4 700R$ uses same transfer case adapter and has same output shaft as a 4x4 350.
    No adapter needed.
    Slight shange in length may need driveshaft mod.

    As for cost without core total for well built newer version better 700R4 is only 1000.
    Go to bowtieoverdrives.com
    Talk with Steve Holmes.
    I replaced a TH400 in my burb so I need an speical output shaft but like a said replacing a TH350 is a straight bolt on.

    My 3/4 4x4 burb with a gas 350 CID 4.11 gears and stock 16 inch wheels and truck tires when from a highway milage of 8 to 10 to a highway milage of 12 to 14 MPG.

    I am very pleased with the 700R4 I got from bowtieoverdrives.
     
  6. slodawg

    slodawg 1/2 ton status

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    700r4 mostly came with np208 t-case. I think on the newer ones its like a 243 or something. To switch it to a np 205 or 203 you have to have an adapter if the 205 or 203 came off a short shaft turbo350 tranny. Ive got both a 700r4 with the np208 factory and a turbo 350 with the np203 factory and no they will not crossover without an adapter.

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  7. 76GMCJimmyinAZ

    76GMCJimmyinAZ Registered Member

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    I was told that the 87 and newer are electronically controlled and won't work with my ol' truck. True? Where can I get the best deal on an R4 and NP208?

    GUZZLES GAS BUT IT'S FREE AND CLEAR!!!
     
  8. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I believe the lock-up torque converter is controlled by a computer, however there are several kits available to adapt these into older trucks.
     
  9. Scoobydoo

    Scoobydoo 1/2 ton status

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    What do you hope to gain from going to a 700R4 ? They are not any stronger than a properly rebuilt T350. If you are just doing this for gas mileage, you will never save enough to offset the additional cost of the tranny. There are alot of GOOD shops in Arizona that will rebuild your 350 with a heavy duty torque converter and RV shift kit for around $600 installed (FYI $300 is just to R&R the tranny out of the truck). I highly recommend the heavy duty torque converter and RV shift kit, money well spent in my book. Also you are running a big tranny cooler aren't you?
     
  10. ken

    ken 1/2 ton status

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    700s are worthless pieces of junk. In our '90 Sub, we are on our 5th one in 250,000 miles. We do not tow anything with it. It never gets 4 wheeled (wife's rig). A buddy of mine just blew his 700 in his '95 Z71. It only had 60,000 miles. He took it to the dealer and had them install a new 700 (for $1800 with 50,000 mile warranty), he picked it up two days ago and yesterday was leaving on vacation and the truck won't go over 45 MPH and the tranny is slipping. What a piece of junk!!! If you're only after mileage, you'll never pay for a conversion that's gonna cost you $1500, cause by the time you do get close to it paying for itself, it'll blow up on ya!!!

    ken
     
  11. 76GMCJimmyinAZ

    76GMCJimmyinAZ Registered Member

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    Well, mileage isn't the only thing I'm after. I'd like to turn a lot less rpm's on the highway- being able to run 70 to 75 on the highway without a) going deaf and b) sounding like my engine is about to explode. Comfort, I guess, is another factor. PLUS, I looked at a link someone recommended on here (bowtieoverdrives.com) and read their little example talking about the difference in rear wheel torque due to the lower 1st gear in the R4 (in my case, getting the boat rolling from stops, etc is the advantage I see) and that only solidified my rationale. I am running a tranny cooler currently, btw.

    GUZZLES GAS BUT IT'S FREE AND CLEAR!!!
     
  12. Kyle89K5

    Kyle89K5 1/2 ton status

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    With all the bad press that the 700 gets, I've got to admit, mine is pretty solid. I've got 186,000 miles on it and no sign of it dieing now (knock on wood). I have'nt been kind to it either. I drive my truck pretty hard, but it's still hoding on. If you're making the swap and really worried about the miliage and dependability issues, you might look into and overdrive or something that bolts into the back of the transfer case. Cole Quinnel (editor of 4wheel and Offroad Mag) put one on his pickup a while ago and judgeing by the way he flogs that truck, I'd say it's holding up pretty good. It's something you ight consider as an alternative. Go with a little steeper gear to help with the low end pull but keep the 350 or 400 tranny for beef.

    Just my $0.02
    Kyle
    89K5
     
  13. Scoobydoo

    Scoobydoo 1/2 ton status

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    What is your gear ratio and tire size? I guess I am confused by you saying you can not run 70-75 which indicates to me that you have a low gear ratio (numerically high) like a 4.56 or 4.11, but if that is the case you should have a low 1st to get the boat rolling? this is also one of the advantages of the heavy duty or towing type converter. It sounds to me that the last time your tranny was rebuilt it was just done stock, like car, but not for heavy duty truck use? Too build a heavy duty 700R4 or a buy a JET you are gonna spend a ton of $$$ especially when you consider that they probably will not except your T350 as an exchange and you will still be paying $300 on top of the price of the tranny for the R&R. But hey its your money.
     
  14. Executioner

    Executioner 1/2 ton status

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    Tubo.............and Slowdawg.
    Whats going on here ?
    One says 700r4 will bolt to a NP205, that came from a th350/NP205 marrage.
    One says 700r4 will not bolt to NP203, that came from a th350/NP203 marrage.
    Please go to court for me, and explain what's going on.
    TIA
     
  15. slodawg

    slodawg 1/2 ton status

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    We'll the 700r4 out of my 86 Blazer has an np208 t-case on it. My 78 Blazer has the turbo 350 tranny mated to a (or was mated to it, it fell to pieces and thus is how I know this) Np 203 t-case. The np208 WILL not bolt to it (the turbo 350) without and adapter. Advance adapters makes one for about $210.00 for this swap but they said I would be drilling new holes in the frame and modify my driveshaft among other things.700r has the long tailshaft and the 350 doesnt. The adapters are nowhere near alike. They may have had one that does fit both but I couldnt find it. Just my opinion and hey I could be wrong.

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  16. Eagle86K5

    Eagle86K5 1/2 ton status

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    I have an 86 with stock 305, 208, and 3:08 gears with 700R4. I just lifted it 2" and put 33's on it. Although there is a definate change in the rpm due to the tires, I just drove the ole gal from Toledo to Nags Head N.C. the truck now has 125,000 miles and the tranny works great. All I have ever done is change the fluid and filter. The hills of West Virgina were a killer, in some places I had to put it into second gear pulling 4000 rpm and 40 mph just to get up some hills. Got home and changed the tranny fluid for the heck of it and found it to be clean. Bottom line is I am not sure why some of you have such a distaste for the 700R4. If you go to the bowtie site and read what they have to say...well if the 700R4 shows up more then others in the NHRA then it should be ok for my 4x4. Just my .02
     
  17. turbo

    turbo 1/2 ton status

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    The rear bolt patern where either the rear extension on 2 wheel drive or the TC adapter is the same 4 bolt patern on a TH350 and a 700R4. The TH400 is quite different and a 6 bolt patern.
    Both the TH350 and the 700R4 have a 27 spline output shaft. The Th400 is a 32 spline.

    The 208 came out in 1981 the 700R4 ccame out in 1982.
    So there are stock TH350 208 combos out there
    The catch in the 700R4 vs Th350 swap is tranny overall length.

    the 700R4 is about 1.8" longer.

    So a transfer case with stock adapter from a TH350 will bolt to back of 700R4 as long as both were 4x4 version with the stock 4x4 version outputshaft. However the unit will move the transfer case and driveshaft mount points by 1.8".

    If one wants to use a 2wd version of the 700R4 to replace a 4x4 TH350 you also need the output shaft change to a 4x4 version.

    But as long as you can deal with length change and both tranny are 4x4 version whatever stock TC case you have should bolt to eather tranny using the stock adapter.
     
  18. 76GMCJimmyinAZ

    76GMCJimmyinAZ Registered Member

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    Holy cow! I sure got everyone going with this one... Let me make sure I understand this. Slodawg, are you saying I can reuse the xfer case I have if I buy this adapter from Advance Adapters? As far as I know, my tranny and xfer case are the original ones in the truck. I hope I do understand you correctly, because I got quoted like $625 (incl core charge due to my non-matching core) for the xfer case. I'd MUCH rather spend $210 for an adapter....

    GUZZLES GAS BUT IT'S FREE AND CLEAR!!!
     
  19. slodawg

    slodawg 1/2 ton status

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    I've even got myself confused with this one. You can go to the advance adapters website http://www.advanceadapters.comand they have a chart with all the adapters they sell and you can cross reference what you want to do.I think its in the v6/v8 section. The 208 I took off the 700r4 woud not bolt to my 350tranny. The stock adapter is different and the output shafts are different on mine.

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  20. getsome

    getsome 1/2 ton status

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    This is what I have "seen" in terms of trany, gearing, and tires:
    My 79CJ7 had 33's, and 4speed manual(t18), and 3.73 gears. It was loud do to a 360ci and a short exhust, and would not do 70mph under 4000rpm's. Fantastic offroad but not practical on the highway.
    My 79 Chevy pickup had 35's, th350, and 3.42 gears and was just about right but ran out of gears on the highway. 4.11 would have helped offroad but would have killed any highway driving that I would do.
    My 84 Jimmy has 35's, 700r4, and 4.11 and is a dog on the highway. First gear is great but it goes down hill from there. I went camping in Nebraska last week and on the highway I had a hard time doing 75mph. If i'd had a choice I would have installed 4.56 or 4.88. Around town is a pain doing 40mph and be in 4th gear at 1200 rpm's. I kept it locked out of 4th for a while and liked it better but gas mileage did suffer. I do like the r4 for the overdrive and improved mileage, and up till now i've had no major problems with it except for one seal. I like the th350 more only because of it's price for parts and rebuildability. Is that a word? I don't know if this helps it's just what i've "seen".

    Getsome
     

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