T20 Transfer Case Issue In My '68

Hey all..... I have a '68 CJ5 that currently has a Dana 20 transfer case in it. Everything works as it should in 2WD and 4WD high range. However, in 4WD low range, only the rear wheels drive, the fronts are not engaged, (it moves around fine, but only with power to the rears)....any thoughts as to what could be going on? Thanks, Dave

 

You mean D20? Dana 20? There is no T20. A '68 came with the Dana 18 from the factory.

The Dana 20 was only used after 1972 in the CJ. Sounds like a shifter problem, not a transfer case problem. If the shifter in a '72 or newer Jeep is not pulled back far enough, it remains in 2WD low range. The shifter has to go all the way back and nearly touch the tool box. Long throw, way back.

First post! Welcome from Boston!

 

Thanks for the welcome! I lived just north of you in Maine until a year ago and moved to Arizona....

It is a '68 with a single stick Dana 20 in it , not the twin stick 18....

I'll see how far it's coming back.... is that shifter engagement adjustable??

 

Are you sure it's a Dana 20?
A 1968 would have had a Dana 18 stock, but it has a single stick shifter.

 

From around '65-up, the D18 was a single-stick, so just because it isn't twin-stick doesn't make it a D20.
A D20 is a straight through drive, where the rear output yoke is in line with the transmission mainshaft. The D18 has the rear drive yoke offset on the same side as the front output. Double-check the rear output to confirm what you have.
The D18 single-stick pattern is (from the firewall) 2H, 4H, N, 4L, so its unlikely this is your problem, unless the interlock pill has been removed.
The D20 does have a very long throw.
-Donny

 

Yep it was replaced by the guy I bought it from...something about the 20 being syncro and the 18 not? Thanks!

 

Thanks Donny its a 20 for sure....

 

First off, welcome from Chester, Mass. Next, do you have a centered pumken on your rear axle, or is it offset? If you have not used it in a while, it could be crud has built up and not allowing full throw from the shifter.

Does it still drive the rear axle in 4 low and just not the front?

 

Dave, transfer cases are not synchromesh. Transmissions are, but not transfer cases. It will be worthwhile to learn a bit more about this.

You can easily look under the Jeep and see whether the rear driveshaft is offset to the passenger side or not. The D18 is offset, the D20 is centered. Because of this offset, the rear axle must be changed to a centered type along with the centered D20 transfer case. Not a trivial change.

Look at the Jeep, take some pictures and post, do whatever it takes to sort this out. Without your cooperation, we can only guess.

 

..corvid.
Finished the sentence for you Glenn.

 

There IS a T20. It just doesn't have anything to do with Jeeps.


Welcome to the site Dave. And yes, someone was feeding you

 

People swap out the 18 for the 20 because the straight through drive is quieter and runs cooler than the 18's offset gear drive. They seem to be less leak prone too.
I think Tim was on the right track with his post above....the shifter has a long throw and you may not be getting it all the way back into 4 low. I'd check for wear and slop in the linkage, also make sure that the hole in the floor is big enough to let the shifter move all the way back.

 

Thanks for the welcome.... the rear axle still drives in 4WD low, but not the front....4WD high works as it should...... I've been driving this Jeep about once a week since I bought it in October....our Ranch in Arizona is surrounded by 56,000 acres of National Forest, so lots and lots of trails and forest service primitive roads..... Dave

 

Thanks Glenn, I'm pretty sure that's what he said... I didn't know any different but I do now ;-)
Dave

 

Thanks! That sounds in line with what he said...I remember something about "quieter"..... I'll check that all out..... I sure appreciate the help..Dave

 

The other advantage to switching to a D20 is moving to the stronger, centered D44 for the flanged axle shafts, since the offset flanged version is so hard to find.
The disadvantages of the stock 20 are 2:1 low range (vs 2.46:1 in the 18) and no option for an overdrive unit. They’re both plenty strong.

 

thanks! good info Dave