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  1. #1

    Default will a engine swap effect my trans?

    I'm about to make my Suburban "MY" Suburban. I found a shop that can do the work and they didn't say I was crazy so thats a huge plus. so I'm thinking about putting a 496(one I'm looking at says it has 690HP) but I may just stick with a 454. but its going to be carb(dual and a scoop) and its a 93 so TBI. will doing the swap effect the trans shifting. the guy at the shop said they could put anything under my hood and have it run but that I should look into this before getting a motor.

  2. #2


    You may have some trouble with the transmission not knowing when to shift because of going to a carb. The transmission in your truck should be a 4L60E assuming it's a 1500. There's 2 issues with that. First, You're looking at shoving a big block in, which has a different bellhousing pattern. 2nd, the factory computer is computer controlled. Your best bet will be to probably swap in a TH400 or an early 4L80 before they went computer controlled. I don't know too many details about these 2 transmissions, but they're ones that should bolt up to a big block and are not computer controlled. I'd suggest a built-up 700R4, but I don't think it came in a big block bellhousing, but would be ideal because of the steep first gear and very good overdrive.

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 265K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

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  3. #3

    Join Date
    Feb 2008
    Red Wing, Minnesota, United States


    that will for sure give the trann yissues, not to mention the rest of the drive train. Your gears wont handle it and you are gonan have to beef up the suspension to handle the extra weight of the engine as well. You may just have to look into a fully built tranny for that kind of motor especially if it will be a daily driver
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual

  4. #4


    Forgot to say its a 3/4ton. so does the 93 3/4ton have a computer controlled trans?

  5. #5


    Yep, no doubt it does. If it's a light duty 3/4 ton with a 350, it's probably a 4L60E. If it's a more heavy-duty 3/4 ton or has a 454, it's got the 4L80E. Either way, it's computer controlled. Your two options are to dump the computer controlled transmission for one of the ones I previously mentioned, or get a standalone transmission controller that will run the transmission. The transmission controller can be a pricy proposition, but you need to weigh the pros and cons and decide on a path.

  6. #6
    Jr. Mechanic LoneWolf'burban's Avatar
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    Apr 2010
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    My 92 GMC running a 4.3 has a 700-R4. It's not computer controlled per-sey bt there are electronics on it that effect the truck. TCC, locks the torque converter to make it perform more as a manual would at highway speeds. But never heard anything being different in bolt patterns between big block and small motors and transmissions. People have swapped 350T and 400T when they jucied their 350's up. From what all I've seen the 4L series transmissions are all computer controlled versions of the 700-R4 with the 4L60 being the new 350T up the 4L80 being the new 400T. I was wanting to ditch my 700-R4 for a 350T until I took it to a trans shop and they diagnosed it with a valve body problem that was fixed quickly. And how much more would a 496 weigh compared to a 454? They're both big blocks?
    Last edited by LoneWolf'burban; 09-04-2011 at 02:03 AM.
    1992 GMC Sonoma GT 4.3
    1984 C20 'burban 454
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