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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: Mstreman on September 23, 2014, 11:13:55 am
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Newbie to the forum: I am contemplating a 350 motor swap given that "Old Blue"-- blew a head gasket leaving NJ 2 weeks ago. All things considered, rather than replacing the head gasket / possible warped heads etc, an engine swap seems simpler/quicker. I have found another 350 motor mated to a THM350 which came out of an 86 C20. I am awaiting confirmation on whether I have a THM350 or 400 Tranny. I have gotten different answers so what was the Original Equipment for an 86 C20 2wd with a 350ci Chev?
I have an apparent donor sedan engine already changed out by a former owner owing to some clamped off emission lines around the manifold. Not having the truck here in Tennessee, It is a guess as to what is in it now. Do I have any issues if I mix or match the THM 350 vs the 400? I believe I have a 2 piece drive shaft.
That said--As long as I am pulling the engine, I thought I might look upgrade the 3 speed for a 4 speed.
I pull the occasional heavy trailer but would like better gas mileage. What are my options? 4-speed Turbo Hydra-Matic 700R4 or ? What 4 speed could I be looking for and will I also need a different driveshaft?
Any advice on what to look out for is welcomed.
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I can tell you a 350 engine was available in a C20
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I can tell you my '86 C10 came with a 350 with a TH400. I also know this was not the norm
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I can tell you my '86 C10 came with a 350 with a TH400. I also know this was not the norm
Not calling you out on this unless it is a very late 1986 what is your 8th digit (letter) of your VIN? Just real interested is all. Never heard of any 350's making it into 1/2 tons unless it was a rare very early TBI model in late 86
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During today's further reading I see that the 4 speed is not a good choice for a PU. Whichever I use of the 3 speeds, the THM350 or 400, either one will bolt up as most of the differences are internal. Anyone know off hand if there is a torque converter difference I should be aware of?
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I can tell you my '86 C10 came with a 350 with a TH400. I also know this was not the norm
Not calling you out on this unless it is a very late 1986 what is your 8th digit (letter) of your VIN? Just real interested is all. Never heard of any 350's making it into 1/2 tons unless it was a rare very early TBI model in late 86
The eight digit in my VIN is a M. I'm also in Canada don't know if that made a difference
*EDIT* first 8 digits are 2GCEC14M
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M is a 350, Them Canadians ya know... I learned something, thanks
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No problem, glad I could help increase your knowledge. :)
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During today's further reading I see that the 4 speed is not a good choice for a PU. Whichever I use of the 3 speeds, the THM350 or 400, either one will bolt up as most of the differences are internal. Anyone know off hand if there is a torque converter difference I should be aware of?
I'm pretty sure the TH400 converter is like an 1" in diameter bigger. Not sure if interchangeable, and I could be wrong about that as well. I also apologize for slightly hi-jacking your post lol.
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The TH350 and TH400 use different torque converters.