dana 20 conversion to 18

In the latest issue of up they were converting a Dana 20 to a Dana 18. It it easy to do? They used a tera low 18 kit. Can you do it without the 18 inturnals? My case is from a j10 with a tera low into it. What's the difference? Couldn't you just move the output and there you go?

 

No. The rear output of the 20 won't bolt where the rear output of the 18 goes, some of the gears are markedly different, the front output is different, etc. etc.

 

The case itself is the same (assuming you have the large center shaft) so all the D 18 guts and gadgets will fit in a 20 case.. I did mone due to the better casting of the later D-20.. I kept cracking my 18 cases..

BUBBA

 

you can add the 1 1/4 gears to a D20 to get a deeper low range

 

So you do in fact need Dana18 internals, and outputs?

 

Yeah pretty much, you need a donor 18 and just the 20 case casting.. everytihng basically bolts on pretty easy.. but be aware that you have to set some bearing clearances and such, not hard but it's not a bolt and go kinda thing..

BUBBA

 

So, is the 20 case really that much better than a late 18 case, like from my '71? Or, are they just an improvement over the earlier 18 cases?

 

Depends on the case. Later cases are stronger. The 20 cases the factory sometimes put 18 guts in are the weakest of the 20 cases, but still an improvement over the the earlier 18 1 1/4" intermediate large hole cases
Some may argue with me but Ive done the conversion so many times and seen the differences in strength and how they hold up no ones going to convince me different.

 

I have had several broken late 1 1/4" 18 cases. I prefer to put the 18 parts into a good 20 case.

 

So, is there a specific 20 case to look for that is the best? ID'd by a casting #? From a specific donor vehicle?

 

Later Jeep Wagon or Pickup. Early to mid 70's to '79 are the best I've found.

 

Does anyone run a j series Dana 20 with a twin stick conversion have an issue with the rear walking our of gear.

 

Seen it a bunch of times. Means there is wear on the gears where they mesh together in the splined area, the shift rails are worn, endplay is out of specs or bearings are worn, or the detent springs are weak. Any of these can cause the rear to jump out. Also endplay of the transmission output shaft if excessive can cause this as can a loose transfer case input gear nut.

I should add that when I build a 20 that I know will be twin stocked I shim the detent springs so they are nice and tight to minimize this problem

 

When I put the tera low kit in everything was good then it started walking out. The main thing I noticeed was the long grove in the rear shift rail. It should have to do with the original shifter being a j shifter. So I could shin it but do you think I should replace the rail with the long grove, with one that dosen't have the long grove?

 

Does anyone have experience with the long grove rear rail?

 

What exactly do you mean by long groove rear rail? Are you talking about the detent groove that is ramped on those? If so you may be able to replace it with a rail that is not ramped but remember these rails come in different lengths and configurations on the shifter end so that would need addressed. I've welded and ground the ramped portion in the past too with success. Tedius but can be done if you're careful.

 

Yes that is exactly what I was refuring to. Could I use a front rail in the rear rail position? Or are the detents in the wrong place? I have a second 20 t-case. Is the ramped rail because of the j shifter?

 

The ramp is because of the shifter style. Can't swap the rails from front to rear or vice verse. Would need one for the rear. There are tons of variations in them for a 20 contrary to popular belief. I know of at least 5 or 6 variations off the top of my head for the 20.

 

I like your weld it and grind it fix. I was thinking I would
weld it then use a lathe to turn it round again, then fix the grove up. I'll try it on my spare case first. It's the same as what I have in the jeep now.