89 gmc sierra 1500


Asked by Anda21 Jan 24, 2019 at 09:42 PM about the 1989 GMC Sierra 1500 C1500 Standard Cab LB

Question type: Maintenance & Repair

Hey every one I have a 4 speed manual tranny with overdrive..its a 89 gmc
sierra 1500 v6 4.3l and Im trying to figure out what tranny i have in it. I went to a
chevy/gmc forum and they said an 89 1500 only comes with an automatic 4
speed with overdrive but clearly wrong so could some one help me out? Also
Im trying to see if i can get a 454 put in.. is it possible? thx

9 Answers


It sound as if the transmission was switched sometime during the trucks life there should be a casting number on the transmission somewhere that will help you identify it my best advice would be to crawl under and get every number you can find on it then google those numbers and the letters gm eventually you will find what you are looking for. And not to be rude.. but it is very possible to put any engine in any vehicle a 454 in a Sierra is definetly possible but for the small amount of horsepower or torque gains you would get you should either go with a 350 small block and a set of heads or just stick with your 4.3 there are tons of performance parts available for those engines there are multiple proven cases of 500 plus horsepower and realistically you could fully build that motor for not much lore than the cost of a big block swap don’t be afraid of cheap parts if you are on a budget build just look at parts specs before you buy if the specs are the same for a cheap brand as an expenisve brand you are paying for looks or names not power..


thx man i knew i could do a 454 i just wanted to be sure also they really didnt have a manual in 89 gmc? it only has automatic?


It’s possible that it came with a manual transmission factory but to be sure you would have to refer to the original owners manual to the truck and verify that the transmission code matches the code that should be in the truck I’m sure there were both manual and automatic trucks built in 89 I have had s10 pickups with the 4.3 and most of them were 5 speeds so if that is any indicator I’d say the Sierra and the Silverado trucks were pretty close to the same drivetrain set up honestly if you want to just make some more power for a street toy you should just look into making yourself a mean little v6 to embarrass those guys with all that big block money


hell ya but the thing is i went to hot rod.com and they said the max bore is .60 which would only give me MAYBE 200 hp. and then its not sure bc ill have to get the block sonic tested now if i want more power would i have to start going more modern with everything on the block? also read the 262 (mine) is the same as the 350 minus two cylinders and has only 2 gallaries and not 3. can you enlighten me a little with what i can do to get more power? thx

1 people found this helpful.

First start small headers and intake are a good start for small gains in order to make power from that set up you can go the displacement route and bore and stroke it and put a bunch of money into the engine parts or you could go the junkyard fast route and buy a turbo off a diesel truck from your local junkyard takeyoir stock exhaust manifolds cut them and make a turbo manifold decal your stock injectors and run a mechanical pressure regulator that would be a way to keep it somewhat old school and fast in order to gain power yes the newer intake and throttle body setups will make more power than a carburetor most of the time.. however the carburetor option is much cheaper to buy if you are buying new parts and you know what you are doing when it comes to the tuning part off things


thx man ya im not trying to get crazy with hp i just want a little ummmph you know. and like alot of people im trying to just figure things out, i've never really worked on building a truck up i've only troubleshot and fixed the issue. I want to learn how to build for great sound and a little more horses like 450hp if i can with a v6? any other things i should know


You could easily make that kind of power from a 4.3 make sure to put money into the rest of the truck as well if you plan for that much power definetly put a good clutch in it doesn’t have to be expensive but needs to be able to support the power you are looking for that is pushing the limits on stock clutch for sure also you should definetly either weld the rear end or buy a mini spool if you plan to put the power to the ground as well as upgrade rear axles at least if not the whole rear end.. at that point your driveshaft is the weakest link and that is not a bad part to have as a weak link considering every car has its weak point and driveshafts are one of the cheaper options lol


Not only that.. 450 hp on stock suspension is gonna be one hell of a wild ride I’d recommend at least putting shocks and springs all the way around if not upgrading to a better suspension setup they make a lot of stuff that uses stock mounts or you can go full race setups and weld your own mounts if you fabricate at all?


thx alot man youve been alot of help i plan i doing all of that! i just want to start with the engine. i think im going to buy a truck thats been sitting with a 327 350 or a 383 in it tear the engine out, tear it down and start from just a block! im super excited to start this and i hope i can get the best help

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