CJ front end

billfish76

New Member
Joined
Nov 6, 2006
Location
Charlotte NC
I have a 79 CJ 7 with a 304, Auto, and Quardatrac. I wanted to know if any of you guys out there have replaced the front end (dana 20???? stock) with one that has locking hubs on a CJ with a automatic and quadra trac. The stock one is full time 4x4. I would like to be able to unlock the front to try to improve gass mileage and power.

Also I would like to drive this jeep on the street and highway so 65mph would be great. What gears should I use with 33's so my motor doesnt work to hard on longer drives.

Thanks for any info,
 
I am not sure about your quadratrack question, but as far as the gearing goes

3.54's, 3.73's, 4.10's

I ran 3.73's with 33's and 35's and it seemed to ride real good on the interstate
 
billfish76 said:
I have a 79 CJ 7 with a 304, Auto, and Quardatrac. I wanted to know if any of you guys out there have replaced the front end (dana 20???? stock) with one that has locking hubs on a CJ with a automatic and quadra trac. The stock one is full time 4x4. I would like to be able to unlock the front to try to improve gass mileage and power.
Click to expand...

Your front axle, if stock is a "narrowtrac" Dana 30 (Dana 20 is a transfer case). IIRC, you shouldn't add locking hubs to the front of a QT without converting the QT to part-time. I know folks like Doug Thorly & others made the conversion kit back in the day, but I believe MileMarker is the only kit left. If you add the locking hubs, the center diff in the QT case will spin the front driveshaft and the rear won't turn. Seems others have used the "emergency" selector to "lock" the center diff though? Probably a BAD idea for longevity & street driving. Bill @ 44Magnum may be able to offer some insight.


billfish76 said:
What gears should I use with 33's so my motor doesnt work to hard on longer drives.
Thanks for any info,
Click to expand...

IMHO, the 3.54s you probably already have will keep the revs down on the road running 33"s. *IF* you have the optional 2.57:1 low-range box on the QT (a bolt-on if you don't), that combo shouldn't be too bad for MILD offroad either. I run 33"s with a 304, TH-400, D20 (2-ish:1) and 3.73s with no problem. Only turns about 1600-1700 @ 55mph and about 2100-2200 @ 65-70mph... the crappy TC ratio does put a crimp on the offroading, but hasn't stopped me from having a good time.

FWIW, you aren't gonna find any miraculous fuel mileage improvements! AMC engine designs are now 40 years old and you'll soon find the point where "it's as good as it'll ever get". And the aerodynamic brickwall design... with flat grill & windshield aren't gonna help mileage either!
 
Thanks for the info, I didnt think that I would be able to unlock the hubs. For the price of the conversion I can change over to a differnt TC. What did you have to do to use the D20 TC??? Becides change the rear.
 
billfish76 said:
Thanks for the info, I didnt think that I would be able to unlock the hubs. For the price of the conversion I can change over to a differnt TC. What did you have to do to use the D20 TC??? Becides change the rear.
Click to expand...

Well, my D20 came stock behind the TH-400. Unfortunately, you're gonna find "converting" yours to any other TC will make the QT part-time conversion look cheap!

The early Jeep "round top" TH-400s used adapters/spacers between the block & bellhousing and a spacer on the crank to mate with both the early "Dauntless" (Buick) 225V6 & the later AMC mills (V8 & I6) found in Jeepsters, Commandos, Waggy's, & J-trucks. Later, AMC had specially cast TH-400s with an AMC bellhousing pattern that allowed them to mate without adapters... this case ONLY had the QT attached. Neither of the versions of TH-400 are externally the same as the Chevy model...

If'n I was in your shoes (& hell bent on ditching the QT), I'd find a rebuildable T(orque)F(light)-727 or 904 or 999 that came ready for a D300 TC. The TFs requires no adapters to mate w/ your 304 and was an OEM Jeep tranny. The D300 is as tough as a D20, has a lower low-range ratio, and is pass. side front output... and best of all, there are *several* (727s/D300s) for sale on this board right now!

IMO, you *might* be fine keeping the offset AMC20 rear axle also.
 
billfish76 said:
Thanks I believe it has 3.54's in it now. I have the chance to get 4.10's but I think they will be to much with 33's.
Click to expand...
The automatic should make it a little more bearable, but I think you're right, 33's and 4.10 gears will run the RPMs a little too high. I ran this for about a year (manual tranny, no OD), kind of sucked though. I finally cured it by going to 35's :huggy:
 
quadra-trac

I have a buddy looking at the same problem. Quadratrac. Does anybody make a rebuild kit for the center diff? It doesnt seem like a bad TC unless you want to go big. Doesn't it have course spline outputs too? The AMC20 axle tubes look smaller than a Dana 35.
 
Back
Top