Author Topic: 1975 chevy k10 transmission swap  (Read 2322 times)

Offline Sawilli95

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1975 chevy k10 transmission swap
« on: September 07, 2017, 11:42:53 PM »
So I have a 75 k10 with a 350 and am looking to swap my transmission out for another manual trans, I currently have what I'm pretty sure is a Saginaw Muncie SM465 manual transmission but I'm looking to put something that doesn't have granny first in it. Any recomendations? Also will I need to change out my transfer case?

Offline 1967KaiserM715

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Re: 1975 chevy k10 transmission swap
« Reply #1 on: September 08, 2017, 09:35:42 AM »
What's your primary use for truck? Typically a nv4500 or nv3500 (a little weaker, and not the best for towing or any off roading) are the best upgrades, and I believe they are all able to bolt up to the current transfer case. You'll want a 96+ transmission for a higher first and internal slave (unless you have a lift an early external slave NV will not fit) you could get an adapter bellhousing as well.

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Offline roundhouse

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1975 chevy k10 transmission swap
« Reply #2 on: September 08, 2017, 10:47:41 PM »
Yep
N V-3500 from a 97-07 full size 4x4 pickup with the 4.8 LS engine (Not from S10, they won't fit)

We used car-part.com to find one , probably won't find one near you , but will have to have it shipped

Don't remember which clutch disc we used , or if the same one from a granny 4 speed will work


Don't know if you will have to swap t cases since you didn't tell us what t case you have
But you probably have a NP-205

The 3500 bolts up right to a 31 spline round bolt pattern NP-208

Most came behind a TH -400 auto Trans although some manual transmission trucks got a 31 spline after a certain. Year , 1982 maybe ?
If you're calling the seller of a NP208 have them text you a close up pic of the splines so you can count them and verify that it's a round bolt pattern to the Trans , a lot of the 208s have a figure 8 pattern and that won't work with the 3500

It's a great 5 speed , we swapped  one in our 76 K-10 to replace the 4 speed granny
« Last Edit: September 08, 2017, 10:51:03 PM by roundhouse »

Offline 1967KaiserM715

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Re: 1975 chevy k10 transmission swap
« Reply #3 on: September 09, 2017, 05:09:55 AM »
Forgot about bolt pattern, they only affect the 203 and 205, the 208 only came in a round pattern. Splines are different as well, being a 75 you likely have a 10 spline.

Advance adapters may make an adapter to mount the nv3500 to the current 205

Then for the np208 transfer there are 2 splines, a 27 and 32 (I don't think it's 31, but I could be wrong and roundhouse correct) 32 spline came behind the th400 and late sm465, 27 behind the 700r4. Not sure on th350 or the overdrive manual(rare)

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Offline roundhouse

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1975 chevy k10 transmission swap
« Reply #4 on: September 10, 2017, 12:02:54 AM »
Forgot about bolt pattern, they only affect the 203 and 205, the 208 only came in a round pattern. Splines are different as well, being a 75 you likely have a 10 spline.

Advance adapters may make an adapter to mount the nv3500 to the current 205

Then for the np208 transfer there are 2 splines, a 27 and 32 (I don't think it's 31, but I could be wrong and roundhouse correct) 32 spline came behind the th400 and late sm465, 27 behind the 700r4. Not sure on th350 or the overdrive manual(rare)

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You're correct
Its32 spline
But I'm pretty sure that they had "figure 8" and "round" bolt patterns on the 208 depending on the year

Anyhow the best place to find a 208 that bolts right to a 3500is from the CUCV army version , they all had TH-400s

You will dad to learn what the TH 400 looked like so you can tell em apart at a salvage yard

And again, don't drive two hours to look at a 208 case without the seller texting you a picture of the splines and bolt pattern and possibly the transmission it's still bolted to

I did it twice , one salvage yard assured me it was a 32 spline from a 400 and after a 2 1/2hour drive one way, it took me 12 seconds to count the 27 splines

Another trip was over an hour each way to see that the seller had a TH-350 and a NP-205
Grab the crossmember too, and make sure you get the adapter extension thing that bolts  between the Trans and Tcase

Offline Irish_Alley

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Re: 1975 chevy k10 transmission swap
« Reply #5 on: September 10, 2017, 09:26:27 AM »
the round pattern 205 will bolt right up to the nv4500. depending on the length of the output shaft you might need a spacer.

cheapest and easiest option imo is the 208 like theyre talking about
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