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70 auto conversion Dana 20. Need help.

Jimman207

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New here. I have a rare set up with a 4speed 165 mated to a Dana 20. It appears to be original as the cross member and hump does not look modified. They are a leaking mess so i need to do something. I have a th350 but I don't think there is a way to mate to the Dana. If I buy a 205 will the cross member / shafts need to be modified? Should I just find a 700r4 with tcase from the junkyard? Has anyone done this and how big of a job is it? Any suggestions? Thanks.
 

6872xtc

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While I don't have actual experience with one of the trucks with a Dana 20, I am betting that you will probably need some sort of drive shaft work no matter which way you go, unless going back with the identical parts.
I have never heard of a 4 speed 165. Is it a SM465? Those were very common and easy to find parts for, including NP205 combinations.

Just saw your post about the trans. The 465 is very common, at least where I am.
I don't know what driveshaft yokes the D20 has , so I still would wonder if you will have to do a little work to swap a 205 in.
You may be able to swap a newer 465 and 205 in easily, definitely easier than an automatic transmission swap.
Yes, the steering columns swap easily between the C series and K series trucks.

I put a 700R4 with a 205 in my '70, but it was a complete build of the truck, and I didn't have the money for an NV4500 back then. It still took some planning and work to get it all the way I wanted it, but it still works great. But I had a transmission built for it, not a junkyard one.
 

6872xtc

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You can think about how you want to use the truck, maybe tell us so that we know, and then ask more questions and we will try to answer!
 

diesel4me

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GM did put some Dana 20's in 67-72 trucks.I have seen only a few over the years,most had straight sixes or 307 V8's and they had a 3 speed Saginaw transmission coupled to them most of the time,and it had a very strange shifter linkage that was part of the transfer case adapter--the SM420 4 speed was an option until '69 or '70,then they started using the SM465..

I have seen quite a few 67-72 GM 4x4's with factory NP-205's ,I would assume the cross members allowed both drive trains to bolt up,but as noted,the drive shafts and yokes may not be the same ,the NP-205 might be longer/shorter front to rear than the Dana 20..

Personally I'd leave it a manual transmission ,especially where its "rare" and if it had a SM420,that has an ever lower creeper gear in first than the SM465..I'd consider a swap to an automatic a downgrade,especially a 700R4..I know overdrive is desirable,but a 5 speed manual & transfer case from a later truck would be better than an automatic that might croak on you at a bad time..
 

Jimman207

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I plan on this being a daily Driver five miles back and forth to work. It is geared with 3:73 and about 2500 RPMs at 55. just lazy and would like an automatic but everybody keeps saying the same thing keep the stick. First gear is really low and I don't plan on using off road. I was reading about the hydraulic clutch maybe that will make things better if I try that.

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6872xtc

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I have a '95 with a NV4500 in it that I daily drive way more than I thought that I would. The hydraulic clutch is definitely softer, but doesn't have quite the same feel as mechanical. It doesn't bother me much though.
As far as the 700R4, lots of guys hate them, but I don't have problems. But I don't run junkyard transmissions, unless I plan on it being a short term one. My big block truck has 40K miles on the 700R4, and my '72 C10 has had one behind the 406 small block for years, no issues.
I did have one '90 700R4 die after several years, but the original owner told me that the trans hadn't been out of it when I got it from him. That was 250K miles. I didn't believe him 100%, but when I pulled it, it made me think that he was right after what I found, but anyway.
Keeping the manual trans will be easier, but you have to decide what you want in the end, and how much you want to put into it.
 
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I Had a 1970 GMC Jimmy with a 4 speed and a dana 20 t case. T ran 35 Kelly springfields and 38 ground hawgs. It was virtually indestrucatable. I would pull the components and rebuild and reseal as nescesary. I believe my truck origionaly came with a straight 6. It had a built 350 when i got it that loved to rev.
 
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