Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

700R4 really a 350 with OD?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MudFrog, Mar 26, 2001.

  1. MudFrog

    MudFrog 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    3,236
    Likes Received:
    0
    Location:
    Daleville, Va
    I was on a website (Don't remember which) but it said the 700R4 is really a TH350 with OD. Is this true? Just seems like everyone goes to a TH350 because they are stronger. I know it is because of the heat problem but are the components actually the same strength?

    89 K5 Silverado
    <A target="_blank" HREF=http://mudfrog.coloradok5.com>http://mudfrog.coloradok5.com</A>
     
  2. bigerik

    bigerik 1/2 ton status

    Joined:
    Feb 24, 2001
    Posts:
    184
    Likes Received:
    0
    Location:
    Sonoma County, CA
    I don't know much about overdrives, but I know that when they (GM? Turbohydramatic?) wanted a tranny with an OD, they based the 700R4 on the TH350. The first gear ratio was changed from 2.52 to 3.06, and the .76 (I think) OD was added. My understanding is that they went almost exclusively to a lockup torque convertor. I heard that early 700R4s had some weakness in or around the OD, but that if you buy a new (or competently rebuilt one), that this problem is fixed. I have a TH350 in one truck and a TH400 in the other truck. I like the TH400, and I don't understand why people would want overdrive. I have 5.13s and I can go 75 mph...wouldn't feel safer going faster. Also, I think that a L480E is an auto tranny with OD based on the TH400, or maybe it's a L460E (one goes in the S10s). Those are electronic and $$$.
    <A target="_blank" HREF=http://www.bigerik.coloradoK5.com>http://www.bigerik.coloradoK5.com</A>.
     
  3. MudFrog

    MudFrog 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    3,236
    Likes Received:
    0
    Location:
    Daleville, Va
    Bigrik,
    The 4L80e is the OD version of the TH400. l had been looking into those also. And yes they are quite expensive.
    Whats the difference in a lock up torque converter and a non lock up?

    89 K5 Silverado
    <A target="_blank" HREF=http://mudfrog.coloradok5.com>http://mudfrog.coloradok5.com</A>
     
  4. Brian 89KBlazer

    Brian 89KBlazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    779
    Likes Received:
    0
    Location:
    Ontario, Canada
    Mudfrog

    BASICALLY, with an autotrans, the torque converter allows the two halves to spin or slip in the tranny fluid multiplying torque. When you get up to speed, this extra torque is not needed and the slipping of the torque converter is only generating excess heat. The torque converter then "locks up" physically linking the two halves together for both fuel economy & efficiency. When you slow down or apply the brake, the halves unlock.

    In my opinion, the 700-R4 is a good tranny and can be built to handle some serious abuse. But like everything, opinions vary!

    Hope this helped
    Brian
    89KBlazer
     
  5. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    I'm not a tranny guy, but since that thats never stopped me before, heres my take on the subject.
    A 700R4/4L60/4L60E are based off a T350, but they are not the same trans, internal parts do not swap around (althow something in there will w/some mods, but I can't remember what it was). The strngth (as in power in-put) is close to the same. Some T350s also had lock-up converters, the last guy is on it, as far as lock-up converters. Think of them as another gear. Samething with the 4L80s and 400s- based off of, but not the same trans. The only trans I know of that is the same in 3-speed and 4-speed is the chrylser(?) torque-flight 727, it looks like it is a 727 with a overdrive bolted to the back.

    Twiztid
     
  6. Wheels

    Wheels 1/2 ton status

    Joined:
    Aug 18, 2000
    Posts:
    638
    Likes Received:
    0
    Location:
    Native Floridian living in Oklahoma, USA
    One other important aspect of the lockup torque convertor is when the throughput is locked up, you will get better gas milage. The slippage that earlier convertors have were known for bad gas milage.
     
  7. MudFrog

    MudFrog 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    3,236
    Likes Received:
    0
    Location:
    Daleville, Va
    So the late model 700's have a lockup converter... ?

    Out of curiosity how much have ya'll typically payed for a 700R4 rebuild? On my old truck the day after I bought it the tranny went.... It cost me about $1000 to have it rebuilt with a 3 month waranty (I think I got ripped off), Especially since 4 months after it was replaced it died on me out of town. There was another $950 from a shop in Williamsburg Va, this one included an 6 month warranty, and 8 months later it died on me. After this I bought a used one from the local salvage yard (they get pissed when you call it a junk yard [​IMG]) for $500 with a 6 month warranty, and sold the truck after this one.
    Anyway point being, I think I'm gonna have to be looking into a new tranny or rebuild in the near future. My tranny now is shuddering a little bit in (I believe) 4th and 2nd (at low rpm). Could this be something else? Please let me know what I should check to diagnose the problem.
    Thanks!


    89 K5 Silverado
    <A target="_blank" HREF=http://mudfrog.coloradok5.com>http://mudfrog.coloradok5.com</A>
     

Share This Page