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Old 01-20-2010, 07:00 PM   #1
HRDROKN
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How to SYE your NV271/273's

Some of you that have followed my 1969 Ford Cummins project know that I was able to fit a Dodge NV271 between the narrow frame rails common with early trucks. I had to make some minor frame modifications, but really not a big deal.

The NV271/273 has been used in Dodge and Ford trucks for several years now and are not all that difficult to find. GM may even use this transfer case, but I have not looked into that. One of the transfer case modifications popular with the off-road crowd is the elimination of the slip yoke output with a fixed yoke design. Several aftermarket companies make kits for various lighter duty TC’s, but none for the NV271/273 series.

One of the interesting things I’ve found with these transfer cases is that 95% or more of the internal parts are interchangeable. A big difference between the Dodge and Ford variants is that the Ford uses a fixed output yoke! Now I don’t want to get into any of the pros/cons of a fixed yoke, you all can research that on your own. What I do want to get into is how to swap a Ford fixed yoke into your Dodge NV271/273’s.

So here is what I’m working with…

In the background (cases split) is a Ford NV273 (donor) and up front is the Dodge NV271....



A closer look at the Ford NV273 internals...





At this point there has been no need for any special tools, just a good pair of snap ring pliers!

Both cases with most internals removed....



I removed both planetary units, but later realized that i didn't need to do this to get to the pocket bearing...



So the big question was if this project was just as simple as swapping shafts... yes and no!

Here is a comparison of the shafts side by side (Dodge on top)....



Note the increased thickness of the Ford shaft....



And here is the big difference.......



The pilot end of the Dodge output was longer...



And the Ford....



So what was the difference on the planetary side to require a difference in length?

The Ford pocket bearing is set shallow into the back of the input shaft...



The Dodge pocket bearing was set deeper....



Removed the Ford pocket bearing to check design and look for any reason why this bearing can't be set for the shaft being used.

Ford pocket bearing removed from input shaft....





It appears that the only reason the Ford shaft was shorter was due to the input splines being shorter than the Dodge input...

Dodge on the right....



So I reset the Dodge pocket bearing to the same depth as the Ford.

Before....



After....



So with that little piece resolved.

The NV273 electric shift has a synchronizer set...



The NV271 is a manual shift with a solid selector or slider...



These two units universally swapped between output shafts. Everything else was identical, so now I will just get everything cleaned up and re-assemble in reverse order.

If anyone has broke a NV271/273 output shaft on your Dodge... you might want to look into this swap, of course that may just shift the weak link elsewhere!



Mark

Last edited by HRDROKN; 01-20-2010 at 07:19 PM.
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Old 01-23-2010, 07:32 AM   #2
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One area of concern to address...

There is no thrust load on that pocket bearing and the radial load must be fairly light as the bearing width is only about .375"... what "if" that bearing were to move or push back out! On any future conversions, I would use a spacer behind the pocket bearing. Can be made from nylon or aluminum rod (I'll post dimensions) as that will be more wear (vibrations) compatible with the pocket bearing. Since I have this case together I will interference fit a nylon spacer up through the input spline, which will ultimately be limited by the transmission output shaft end.

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Old 01-25-2010, 04:05 AM   #3
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Just waiting for the input and output seals.... and she is done!



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