1970 blazer swap
Thread Starter
Teching In
Joined: Mar 2019
Posts: 4
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1970 blazer swap Hi all - new guy here. I am planning my first LS swap for my 1970 K5 Blazer. My plan for saving time and money is to buy an entire running truck then swap everything over to the k5. This blazer was originally 350/sm465/Dana20 & I 100% want to keep it a manual which leads me to my question: what will fit the blazer better 4.8/nv3500 or 6.0/nv4500?
My blazer will be on road 100% of the time (no off-roading) - it will be a fair weather cruiser/very little interstate driving.
There are such mixed reviews about these trans options:
nv3500 - weak but good gear spacing...etc
nv4500 - strong but bad gear spacing... etc
any suggestions?
My blazer will be on road 100% of the time (no off-roading) - it will be a fair weather cruiser/very little interstate driving.
There are such mixed reviews about these trans options:
nv3500 - weak but good gear spacing...etc
nv4500 - strong but bad gear spacing... etc
any suggestions?
Teching In
Joined: Feb 2019
Posts: 49
Likes: 1
From: Wyoming
Mines an 85 k5 with a 6.0/nv4500, the nv3500 and 4500 are pretty close to the same the nv4500 is cast iron case so it is heavier but way more durable. The nv4500 is gear oil specific to a gl-4 oil or you will mess up the synchros. There is an internal and external slave cylinder version the the nv4500, I recommend the internal slave to clear exhaust piping and the front driveline. The output is 32 spline on the tranny so if your not in the market for an expensive t case adapter you're going to want a np205 or np208 32 spline input with the round pattern to match up, these came behind 4 speeds and th400 trucks and blazers from 75-91 depending on vehicle. The trannys themselves are the same length as the sm465 so you could reuse your drivelines with little to no modification depending on your setup along with the factory crossmember. Either tranny would be good but I did the 4500 so I would have no worries, I broke a couple of 3500s behind a 350 in a previous k5 I had. Any questions ask away.
TECH Regular
Joined: Dec 2011
Posts: 420
Likes: 115
If possible, drive both, and see what you prefer. I look at it this way: The Blazer will be lighter than either donor vehicle, and it doesn't sound like you are shooting for beefing up the engine, so I would think either would live fine in the application. I'd go for the 6.0, just because I'd want the bigger engine 
However, I would think the creeper 1st gear would get old after a while with NV4500.
Do you know what axle gears you have? And what tire size you will run? That might have an impact on your decision, also. I'm guessing 3.73s if they are stock. With reasonable axle gears, either 3.08s, 3.42s or 3.73s, then you could get by without the overdrive trans, and keep the 465 if you like the way it shifts.
BTW, I think your original t-case should be an NP205, not a Dana 20.
Below is my 71 Jimmy, I run a LQ4 and 4L65e, very happy with this setup. It was originally the same as you- 350/SM465/NP205, but the engine had been swapped to a pretty gutless 283 by a previous owner. I like manual transmissions, in general, but I like the auto in this application. Ours is also just a street cruiser. I run an NP208 t-case, 33s, and 4.56 gears.
http://67-72chevytrucks.com/vboard/s...d.php?t=770894
However, I would think the creeper 1st gear would get old after a while with NV4500. Do you know what axle gears you have? And what tire size you will run? That might have an impact on your decision, also. I'm guessing 3.73s if they are stock. With reasonable axle gears, either 3.08s, 3.42s or 3.73s, then you could get by without the overdrive trans, and keep the 465 if you like the way it shifts.
BTW, I think your original t-case should be an NP205, not a Dana 20.
Below is my 71 Jimmy, I run a LQ4 and 4L65e, very happy with this setup. It was originally the same as you- 350/SM465/NP205, but the engine had been swapped to a pretty gutless 283 by a previous owner. I like manual transmissions, in general, but I like the auto in this application. Ours is also just a street cruiser. I run an NP208 t-case, 33s, and 4.56 gears.
http://67-72chevytrucks.com/vboard/s...d.php?t=770894
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Thread Starter
Teching In
Joined: Mar 2019
Posts: 4
Likes: 0
If possible, drive both, and see what you prefer. I look at it this way: The Blazer will be lighter than either donor vehicle, and it doesn't sound like you are shooting for beefing up the engine, so I would think either would live fine in the application. I'd go for the 6.0, just because I'd want the bigger engine However, I would think the creeper 1st gear would get old after a while with NV4500.
Do you know what axle gears you have? And what tire size you will run? That might have an impact on your decision, also. I'm guessing 3.73s if they are stock. With reasonable axle gears, either 3.08s, 3.42s or 3.73s, then you could get by without the overdrive trans, and keep the 465 if you like the way it shifts.
BTW, I think your original t-case should be an NP205, not a Dana 20.
Below is my 71 Jimmy, I run a LQ4 and 4L65e, very happy with this setup. It was originally the same as you- 350/SM465/NP205, but the engine had been swapped to a pretty gutless 283 by a previous owner. I like manual transmissions, in general, but I like the auto in this application. Ours is also just a street cruiser. I run an NP208 t-case, 33s, and 4.56 gears.
http://67-72chevytrucks.com/vboard/s...d.php?t=770894
However, I would think the creeper 1st gear would get old after a while with NV4500.Do you know what axle gears you have? And what tire size you will run? That might have an impact on your decision, also. I'm guessing 3.73s if they are stock. With reasonable axle gears, either 3.08s, 3.42s or 3.73s, then you could get by without the overdrive trans, and keep the 465 if you like the way it shifts.
BTW, I think your original t-case should be an NP205, not a Dana 20.
Below is my 71 Jimmy, I run a LQ4 and 4L65e, very happy with this setup. It was originally the same as you- 350/SM465/NP205, but the engine had been swapped to a pretty gutless 283 by a previous owner. I like manual transmissions, in general, but I like the auto in this application. Ours is also just a street cruiser. I run an NP208 t-case, 33s, and 4.56 gears.
http://67-72chevytrucks.com/vboard/s...d.php?t=770894
Gears are currently 3.08. I’m thinking tires will be 33x10.5.
Some 69 & 70s came with the Dana 20 tcase - somewhat odd.
Your jimmy looks great - I’m on the 67-72 forum too. I remember reading your thread when you posted it.
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