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Low range Dana 20

1K views 11 replies 6 participants last post by  CJ-Jeeper 
#1 ·
I currently have a Dana 18 mated to an SM420 with an AA Adapter. I am interested in converting to a Dana 20 so I can change out my rear axle to a centered diff. (its a 70' CJ5 with stock 44)
Has anybody swapped the gears from an 18 to a 20? I need to know if I can do this and still use my adapter for the tranny. The adapter uses a new main shaft for the tranny so I want to be sure that the 18 input gear will work in the 20.
Will any Dana 18 gears work for this swap or do I need to check to see if I currently have a compatible 18.
Any advise on this is greatly appreciated.

Also, if anybody knows any good articles covering this topic please let me know.

Thanks for helping the Newbie!:eek:
 
#2 ·
#4 ·
I have not done exactly what you are doing, but I did put D18 guts into a D20 case.

The 18 has to have the 29 tooth bull gear, not the earlier 26 tooth one. Then you need an output gear from a Bronco D20 (or you can the whole gearset from a Bronco D20) You will need a complete D20 for this project, the D18 only supplys the gears, you have to use D20 output shafts, housings, shift rails, forks etc. You might be able to use the D18 case, but it might not have the second shifter hole drilled in the back of the case. (Mine didn't) If your D18 has the large hole index, ~4", then a D20 will bolt right up to your adapter. If your D18 has the small hole index ~3.15", then you will probably have to modify it and use it and all D20s are large hole. The good news is, if your '70 D18 is original and came behind a V6 then it has the right gears and the D20 will bolt up.
 
#5 ·
If you swap all the D18 gears into a D20 case all you'll have is a large hole D18. That will not give you a centered rear output. I "Think" the input gears are the same for a d18 and a d20 but the rest of the gear are not. By swapping to a d20 you will cut your low range by 20% if you don't use a low gear set. The d18 has a 2:46 low and the d20 has a 2:01. I personnally like the offset rear, it keep my pumpkins in alignment. It's easier to line up for me.

Keith
 
#7 ·
You must have an early '70, they changed to flanged axles later that year. You don't have a Warn OD do you? If so, you know you can't use it with a D20 right.

Another thing you could do is find a full size centered axle, (like say a 9" out of an F-150) and narrow one side only. Then you'd have a better axle than the D44 and not have to mess with the transfer case.
 
#9 ·
Not sure what a shop charges to narrow an axle, but what ever it usually is, since you only want one side narrowed it should be around half of what it usually costs. On the axle shaft, they will cut it down and cut new splines onto it. Unless it necks down to where they can't do that.
 
#10 ·
If the full size you start with is say 65" wide & you cut off 7" on 1 side, It's still 58" wide. Quite a bit wider than your front axle.
Just something to think about.
On the other hand, if you start with a Waggy, EB or Scout rear, it would come out pretty close.
 
#11 ·
I couldnt imagine it costing you more than $200.00 but that is a guess. If the scout(5 on 5.5) is used then all the shop needs to do is remove the desired amt of tube and weld the flange back on, then take the axle to a machine shop and have it resplined to the correct length.Done.
 
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