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Transmission swap question, I'm stuck....

Discussion in 'GM Powertrain' started by Scotty1122, Jul 3, 2011.

  1. Scotty1122

    Scotty1122 New Member

    I purchased a rebuilt transmission with some heavy duty/performance goodies built in it. I got my old trans out (4l60e) and when comparing to the replacement I noticed a couple differences.

    One was the bell housing on my original has a top center mount bolt and the replacement does not. The housing looks to be interchangeable.

    Two was the coverter shaft appears to be different. It comes with its own coverter so fitment there shouldn't be a problem. The issue now is that the coverter bolt pattern is slightly smaller on the replacement. My flywheel looks to have two sets of holes in it. Is it possible its "universal"?

    The original transmission is splined all the way to the end of the shaft but the replacement has a inch or two of smooth shaft sticking out past the end of the splines.

    Here's my info:
    2000 Silverado 2wd extend cab
    5.3 liter Auto 4l60e

    the replacement:
    off of a 1998, 4l60e.

    I'm outta money and outta ideas at this point! Maybe I can get a flywheel for a 1998?
    Any info would help, and is greatly appreciated!

    Scotty
  2. MrShorty

    MrShorty Moderator Staff Member 1000 Posts

    It is interesting to see some of these differences. I had seen discussed in many places that there were differences between the OBS and NBS 4L60e's, but I had never seen those differences spelled out.

    Because of these differences, most discussion I've seen say not to swap between OBS and NBS 4L60e's. I haven't seen any discussions about what to do force an OBS 4L60e into an NBS truck. If you figure it out, be sure to post it so future swappers will know how to make them fit. If you can't find any info on making it fit, it might be easiest to trade the '98 4L60e for an NBS ('99 new body style up to ??) 4L60e.
  3. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts

    It sounds like you've sorted out your issues already. I believe with the later year 4L60E transmissions, the bellhousings were removable and swappable, so if your original bellhousing's still good and the mounting bolt patterns are the same, (they should be) swap 'em out. Also, if there's a set of holes in the flexplate that match up with the torque converter, you're golden. Bolt it up and rock on. Also as far as I know, other than minor fixes/improvements, the transmission internals haven't changed it well over 20 years.
  4. Scotty1122

    Scotty1122 New Member

    Ok....what I have found was that I could use the tranny the way it was. However I would lose two bell mounting bolts.

    Or I could use the original bell with the replacement tranny. However the original bell was deeper than the replacement bell. So I just used the replacement as it was. I figured the original would hold the tranny back too far for the coverter to set right on the shaft. And the top center bolt and one of the bottom bolts were nearly directly opposite each other.

    Bolted up, topped it off, and tested. Works good, got it up to temp and topped off a little more and seems to be doing good.

    We'll see how it does this week.
  5. silveradotrailblazer

    silveradotrailblazer New Member ROTM Winner 1000 Posts

    Welcome to the club. Sounds like it all worked out for you.:sign0173:
  6. dsfloyd

    dsfloyd New Member ROTM Winner 1000 Posts

    glad to hear it seems to work out
  7. franksterjr

    franksterjr New Member

    I've heard 4L60E's are all the same with many minor outward differences. I'm trying to put a 98 S-15 Blazer trans in my 98 K-1500 Pickup. Once I pulled the transfer case and adapter off, the shift arm and the cable bracket, they are identical (or so they seem). The numbers on the torque converters list them both for a 4.3, 5.0, or 5.7. The bell housings are identical. One trans shop told me the guts were the same, another told me they were completely different and I would blow the trans out almost immediately. We'll see.
  8. franksterjr

    franksterjr New Member

    Got the transmission in. I've been driving the truck for 5 days now, feels good, shifts good, torque converter has a slightly higher stall speed. I think it feels better. The transmission from an S-15 Blazer with a 4.3 will definately work in a K1500 (or C1500) with a 5.0 or 5.7. How long will it last? We'll see.

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