Do you have to regear the tranny when going from a 305 to a 383?

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Jimbo2312

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hey guys, doing a swap from a 305 to a 350, it’s a .30 overbore with upgraded internals so technically a 383.. I’m a little nervous with the transmission though. Any thoughts? Thanks!
 

Drunkcanuk

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Not sure what you mean by regear the tranny.
You probably have the 4l60e if it's a 95. Not the most stout transmission out there. If you are careful and don't bag the $hit out of it, you will probably be ok.

I'd say run it until it goes boom, then either rebuild it, throw another stock one in until it expires as well or do a 4l80 swap.
 

Jimbo2312

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Not sure what you mean by regear the tranny.
You probably have the 4l60e if it's a 95. Not the most stout transmission out there. If you are careful and don't bag the $hit out of it, you will probably be ok.

I'd say run it until it goes boom, then either rebuild it, throw another stock one in until it expires as well or do a 4l80 swap.
Not sure what you mean by regear the tranny.
You probably have the 4l60e if it's a 95. Not the most stout transmission out there. If you are careful and don't bag the $hit out of it, you will probably be ok.

I'd say run it until it goes boom, then either rebuild it, throw another stock one in until it expires as well or do a 4l80 swap.
So every 4L60 or 700 have the exact same gears in them? I thought they might be geared different according to different motors.. I’m pretty green with this, thanks for bearing with me
 

Drunkcanuk

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No worries, have to start learning somewhere, and for these trucks, there is no better place!

As far as I know, they are all geared alike. I could be wrong, but am pretty confident I'm not. But if I am, someone will be along to set me straight. It's probably something easy to look up.
 

Jimbo2312

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Thanks man, appreciate it big time. I’ve had this truck 10 years, absolutely love them and looking forward to holding onto it, hard to beat for ease of working on
 

RDF1

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A 350 bored .030 should be a 355ci if you have the stock crankshaft.



All of the 700r4/4l60/4l60e/4l70e have the same gear ratios.



Some of the 2009+ had a different 2nd gear ratio but nothing crazy different.

Now a couple companies do make different gear sets but they are silly expensive.
 

Jimbo2312

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Just clarified this with the motor builder; stock 350 crank. This truck was stock with a 305, so I think all I have to do is swap the ECM and potentially a remap.. sound about right? Very good news with the tranny though thanks guys
 

GoToGuy

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Do have the service manuals for your year if not download them here in the forum. A Lot of your basic questions can be quickly answered in the manual. How did or who told you a 305 , thirty over gets you 383 ?
383- bore 4.005, stroke 3.800 :3811797817_8d685371
 

Das Hatt

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I'm confused about the displacement as well. so let me see if I have this straight

1. originally this stock motor was a 305
2. It now has a 350 crank.
3. The block has been bored .030 over.

If that is the case, the 350 crank has the same stroke as a 305. So you get no added displacement. If the block has been bored .030 over, you don't have a 305 anymore, you have a 310.

If you want a 383, you need to start with a 350 block, then have it bored .030 over, remove the 350 crankshaft and put in the crankshaft from a 400.
 
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