Rebuilding Hybrid Dana 20 using T & J parts

[JWMcCrary]

I have several transfer cases and need to rebuild one to replace the one I'm running now. I want to do it using the best parts from each, basically a hybrid T & J.
I ordered the new shift rails from JB Fab that they claim are designed to help with popping out of gear so will use those with all new bearings and seals.

Use a J case
Use T gears
Use J front output shaft

what else? and am I correct on the above?

I have WH HD output on the case I'm running now that will be used on the rebuilt case.

Also, how do you identify T vs J gears? I have a box full of gears that I got a few years ago that I'm not sure what they are.

 

[Viperwolf1]

No difference in the case itself. Use the one that looks best. Your plan is good. It's really just the cluster gear and sliding gears that need to be swapped.

The gears have an ID number on them, 18-X-XX or something like that. If you list what they are I can probably tell you which case they go to.

 

[JWMcCrary]

When you say cluster gear, you are talking about the double gear in the center that the idler shaft goes through correct?

 

[Viperwolf1]

When you say cluster gear, you are talking about the double gear in the center that the idler shaft goes through correct?

Correct.

 

[JB Fab]

The "T" type gears have a slightly lower low range ratio.
FYI: During the crossover from "J" to "T' (72-73) type, (72-73) it was not uncommon to to have a stock "T" type case with a "J" type front output from the factory.

 

[Viperwolf1]

FYI: During the crossover from "J" to "T' (72-73) type, (72-73) it was not uncommon to to have a stock "T" type case with a "J" type front output from the factory.

During the serial number range of about 168xxxx to 173xxxx.

 

[mrdrnac]

Does anyone have a source or a part number for the thrust washer that you use on the J Shaft when you are replacing the T shaft and the snap ring? Thanks

 

[JWMcCrary]

No difference in the case itself. Use the one that looks best. Your plan is good. It's really just the cluster gear and sliding gears that need to be swapped.

The gears have an ID number on them, 18-X-XX or something like that. If you list what they are I can probably tell you which case they go to.

UPDATE - This went well. I tore down 2 cases, T case and J case to (hopefully) know for sure what was what. The only difference in the gears that I could find was the low side(small) of the cluster gear. The sliding gears looked identical to me. However I did keep all the T gears together and used the J front output. Went together nicely.

Just throwing this out there for info on what I found. Viperwolf1 has certainly been into more of these than I have, seems odd to me you can only have 1 gear with different number of teeth between a T and J. But I did the math and it works for the ratios.

 

[Viperwolf1]

The difference in the sliding gears is the diameter. Same tooth count but different diameter to make up for the smaller cluster gear.

 

[JWMcCrary]

The difference in the sliding gears is the diameter. Same tooth count but different diameter to make up for the smaller cluster gear.

Certainly makes sense. I didn't put a caliper on them, just laid them one on top of the other. I could see them easily getting mixed up.

 

[Viperwolf1]

If you do mix them up you will find out as soon as you try driving in low range. It makes lots of scary noises.

Here are the sliding gear numbers:
18-8-35 T
18-8-37 T
18-8-57 Early J
18-8-58 Early J
18-8-65 Late J
18-8-66 Late J

 

[welndmn]

I did the J front output swap on mine years and years ago, at the time time I sent everything out to be cryo treated as well (gears,output shaft, and yokes), it preformed flawless for me, before that I seemed to snap 1 front output shaft a year.
I can't tell you if J shift output isbetter or not, the main reason I did the swap was the J shift front output can be replaced without disassembling the transfer case, that was the only reason I swapped. I think the girdle / thicker inspection cover added the most strength.
I sold the case after about 5 years of running it like that.

 

[JWMcCrary]

I think the girdle / thicker inspection cover added the most strength.

Interested in how thick? I have the billet aluminum cover on m7 73 and have considered it for the other one. Wasn't sure how much strength it added and if any ??? Sounds like you are saying ts worth the dollars...or maybe make a thick one out steel late?