Stock 350 3/4 ton transmission options

[AC89K2500]

That truck would have a SM465. Essentially a 3spd with a granny low. I do not know of anyone that actually uses 1st gear in them unless they are starting off uphill with a heavy load or trailer. Even the shift knob on most of them has L-1-2-3-R.

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This is the trans I have in my truck. I just considered it “3 spd” because I don’t use the low gear at all. Nonetheless, I still like the idea of a 4l80 swap as I live in the city and commute to work on the interstate. I think that an automatic is a better all-around fit for my driving style. I will be checking out a few of the other threads I’ve seen posted as well, but figured if anyone on here had some sort of list of all of the parts I’ll need to acquire before I render the tuck immovable, it would considerably speed up my build process! Thank you all for your input!

 

[99xcss4]

a th400 would be a more easy swap if you can find one a 4l80e is going to require a wire harness swap and computer swap or a stand alone control unit either is going to require a different crosmember a steering column swap or mod unless you put a floor shifter in you could most likely get a way with a 700r4 or 4l60 but they are weaker and you would need to change the input shaft on you t-case for them manuals th400 and 4l80e use 32 input a 700r4 4l60 4l60e as well as a th350 use a 27 spline input you will aso need to get your dive shafts lengthend or shortend or swap them from the truck you get your transmission from

 

[L31MaxExpress]

a th400 would be a more easy swap if you can find one a 4l80e is going to require a wire harness swap and computer swap or a stand alone control unit either is going to require a different crosmember a steering column swap or mod unless you put a floor shifter in you could most likely get a way with a 700r4 or 4l60 but they are weaker and you would need to change the input shaft on you t-case for them manuals th400 and 4l80e use 32 input a 700r4 4l60 4l60e as well as a th350 use a 27 spline input you will aso need to get your dive shafts lengthend or shortend or swap them from the truck you get your transmission from

He wants the overdrive. No changes are needed to the column.

 

[AC89K2500]

interesting 91 model year should be 4l80e not 400 op claims to have a 3 speed manual unless that got swaped in at some I think the op has a sm465 and the shift pattern is confusing him

Wasn’t sure of trans model name, that would’ve been more informative, on my end, from the boot! My apologies. I’ve never touched the low gear on this truck and assumed most people didn’t unless it was under load. I basically drive it as a 3 spd and it works fine and shifts smooth. But I’d like something a little more practical for busy city/interstate use and thought (though I’m aware I’m in for a hell of a project) the 4l80 would be my best and most reliable auto trans option that I can still use in HD applications. I’m only really experienced in body work/paint so I decided to come here for as much advice as I can get. I’m certainly learning that’s for sure!

 

[AC89K2500]

a th400 would be a more easy swap if you can find one a 4l80e is going to require a wire harness swap and computer swap or a stand alone control unit either is going to require a different crosmember a steering column swap or mod unless you put a floor shifter in you could most likely get a way with a 700r4 or 4l60 but they are weaker and you would need to change the input shaft on you t-case for them manuals th400 and 4l80e use 32 input a 700r4 4l60 4l60e as well as a th350 use a 27 spline input you will aso need to get your dive shafts lengthend or shortend or swap them from the truck you get your transmission from

Im aware a 4l80 swap won’t be a cake walk, I bought as a project truck because its got good bones but the current setup isn’t practical for what I’ll intend to use it for. I’m looking into purchasing a parts truck to (hopefully) get all I need in one swing. Just curious what all parts will need to be swapped as I’m not that experienced in the mechanical side of the project. It’ll look pretty when I’m done with it but just seeking any wisdom I can get on the “organ transplants” so to speak!

 

[NickTransmissions]

Im aware a 4l80 swap won’t be a cake walk, I bought as a project truck because its got good bones but the current setup isn’t practical for what I’ll intend to use it for. I’m looking into purchasing a parts truck to (hopefully) get all I need in one swing. Just curious what all parts will need to be swapped as I’m not that experienced in the mechanical side of the project. It’ll look pretty when I’m done with it but just seeking any wisdom I can get on the “organ transplants” so to speak!

Did you read @Astro 's thread that I replied with in post #2? I believe everything you're asking about when it comes to 4L80E swaps is all there. It's why i replied with it (and my thread in case you wanted to overhaul the 4L80E as well).

 

[AC89K2500]

Did you read @Astro 's thread that I replied with in post #2? I believe everything you're asking about when it comes to 4L80E swaps is all there. It's why i replied with it (and my thread in case you wanted to overhaul the 4L80E as well).

I will take an in depth look into this tomorrow when I’ve got time! Thanks a ton @NickTransmissions hopefully this will get the ball rolling!

 

[99xcss4]

He wants the overdrive. No changes are needed to the column.

dosent he need a column shifter unless he puts in a aftermarket floor shifter that is why I said swap or mod the column

 

[AC89K2500]

dosent he need a column shifter unless he puts in a aftermarket floor shifter that is why I said swap or mod the column

I intended on having to replace the column to accommodate for the shifter. I’m sure there are plenty of them available at my local junk yards as I’ve see hundreds of gmt400 trucks on the lots. Intended on a cluster swap as well and I prefer the look of the later model dash so (eventually) would like to do that too

 

[99xcss4]

this is one of the cheapest stand alone options you do have to manually shift it though there is a cheaper one yet but in addition to having to manually shift it you also have to manually lock and unlock the torque converter with a switch https://www.ebay.com/itm/1562390722.../YJhelZBz3we88S1cjGryYO7xw==|tkp:BFBM4KyikKRk https://www.ebay.com/itm/2859952391...0zGRa0enpXt5VhI8OW9XQVlQ==|tkp:Bk9SR7SDwpCkZA you can get a one that has auto lockup and shifts on its own but they are a few hundred or you can go this way if you want to

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