Out with the old, in with the new

[Viperwolf1]

I finally got tired of my externally lubed transfer case and inconsistently shifting C4. I built up my spares over the last couple of months. The new tcase was originally a T-shift that I converted to a J-shift for the lower gearing.

The new C4 came from a '73 and it needed more than a few parts to get it back in working order. The forward clutch was fried and the front planetary gear was seized. Luckily I also had a parts C4 with some good planet gears. I drilled the rear of the case to provide oiling to the #9 thrust washer, modified the stator support for full flow to the external cooler, installed 5 Raybestos frictions in both clutch packs and installed a Transgo reprogramming kit. I also paid particular attention to the clutch pack clearance and used some selective snap rings to make them perfect. It should be good and strong and hopefully last longer than the 60K miles I got out of the old C4 stock rebuild. Total cost was about $350 for all the good parts.

The only thing noteworthy about the new D20 is that the speedo drive gear has one less tooth than the old D20, so I need to come up with a new driven gear now. Ironically the one I need is the same one I had before I changed to 4.10 gears and I can't find the old one now.

 

[Broncobowsher]

I did that same speedo gear thing, but I kept my old one and knew where it was at. Changing to 4.88 gears and 33's geared it the same as stock and 4.10s. At least it did for the speedo gear. The overdrive shure makes it drivable on the highway.

As for the difference in drive gears. I have known this existed for years. But so few people know about it. I am trying to get a few data points for what driving gear came from what application. I suspect that low geared factory vechiles had the less tooth count and the higher geared had more. Do you happen to know the original gearing in the axles for each of the transfer cases?

 

[ak68]

Did the J shift transfer case already have a lower gearset or did you mean you swapped the J for a T since in original gearing the T is lower than the J.

 

[Broncobowsher]

I think he means the lower T gears into the newer J case. Not much difference, but if you have all the parts just sitting there, why not?

 

[Viperwolf1]

I did that same speedo gear thing, but I kept my old one and knew where it was at. Changing to 4.88 gears and 33's geared it the same as stock and 4.10s. At least it did for the speedo gear. The overdrive shure makes it drivable on the highway.

As for the difference in drive gears. I have known this existed for years. But so few people know about it. I am trying to get a few data points for what driving gear came from what application. I suspect that low geared factory vechiles had the less tooth count and the higher geared had more. Do you happen to know the original gearing in the axles for each of the transfer cases?

You are correct about the gears. This new one with one less tooth came from a '73 with 4.10 gears stock. My old one had 3.50 gears stock. I didn't think to make note of the tooth count or get a pic of of it but it makes sense mathmetically. It's about 12-13% off now and it was within 2% before. I'll let you know what the count is in the old D20 when I get it apart.

 

[Viperwolf1]

Did the J shift transfer case already have a lower gearset or did you mean you swapped the J for a T since in original gearing the T is lower than the J.

I actually took a low geared T-shift case and swapped the shift rails to make it a low geared J-shift.

 

[Viperwolf1]

You are correct about the gears. This new one with one less tooth came from a '73 with 4.10 gears stock. My old one had 3.50 gears stock. I didn't think to make note of the tooth count or get a pic of of it but it makes sense mathmetically. It's about 12-13% off now and it was within 2% before. I'll let you know what the count is in the old D20 when I get it apart.

Damn, I lied! I did get a pic. Looks like 6 teeth.

I just looked at the old tcase gear. It definitely has 7 teeth. It's a plastic gear.

 

[sprdv1]

Looks great brother. Thinking of going silver on my tranny too, not sure yet

 

[Socal Tom]

Looks good. When I put in the C4 I had them rebuild my spare t-Shift and put that in too. For about a month I could park and not leave a spot on the ground. Then I got the oil changed, and the front drain plug stipped on the Engine oil pan and now I leave a little puddle.
Tom

 

[1sicbronconut]

Looks great brother. Thinking of going silver on my tranny too, not sure yet

This stuff works great, and I used the cast iron paint for the t-case. http://www.eastwoodco.com/jump.jsp?itemID=131&itemType=PRODUCT

 

[kbldawg]

That looks and sounds like a reall nice rebuild. I love seeing the pros work!

 

[777mechanic]

hey phil you forgot to tell them that you rebuilt mine the week before and also resealed and gasketed my transfer case . man your a busy retired guy haha .

 

[Viperwolf1]

hey phil you forgot to tell them that you rebuilt mine the week before and also resealed and gasketed my transfer case . man your a busy retired guy haha .

Ha ha. I'm only busy between periods of extreme boredom.

I have been able to get some seat time in it today. It will bark 2nd and 3rd. 3rd gear comes on pretty much instantly with the extra clutch and drilled drum. 2nd gear is very quick but not as quick as 3rd. Maybe because I used a carbon band. I believe the coefficient of friction is less but the durability is much better. I thought I had a leak at the modulator yesterday. I checked it out today and it was just a loose cooler line. I also ran some extended vent hoses to the upper firewall for both the C4 and D20. All is well under my Bronco again.