J vs T shift dana 20

bknbronco · Oct 21, 2017

If i already have a T-shift dana 20 what advantage does a J shift have over the T as far as off road strength. Im not concerned with how one shifts easyer than the other. I have a T-shift now and it shift like butter. I want to know how to build a heavy duty dana 20.

Both cases benifit from a HD rear outputshaft upgrade? (i can do that to my T)

Alot of guys take the J shift and just install the T-shift LOW gears? (I already have that in my T)

Is the j-shift front output shaft alot stronger? Can i put that shaft in my T-shift case?

Whats the weak points in either dana 20??

bknbronco · Oct 21, 2017

if i can keep my t-shift and down the line add a HD rear outputshaft when i make up a new rear driveshaft that would be both easy and cheep. But is there other benifits of the later J-shift?

DirtDonk · Oct 21, 2017

Subscribed to see what others like Viperwolf have to say. But one other difference is that the T case has a lower low range. Just by a smidge, but it's there.

Paul

bknbronco · Oct 21, 2017

Hows it been paul??? ya i have seen viper built dana 20's on this site for 10 years and im assuming he likes the J-shift but takes the LOW gear out of the T-shift. I have a line on both style and would love to build a HD unit but from what i can tell from my research is that the only thing the later j-shift case has is a better front outputshaft...how much better we will hear from the guys. And can i just put that front output shaft in my T-shift?

DirtDonk · Oct 21, 2017

Havin' fun here!
Good question about if one is stronger or not. Not sure about that bit, but I think the basic housing/case is the same in overall strength.
Interested to hear what works and what doesn't for you.

There are the lower gear sets as well, like the O'Brien or the Crawler gears (https://www.wildhorses4x4.com/produ...er_Case_Gears_Kit/Bronco_Dana20_Transfer_Case) (hey, good place for a sales pitch, right?

), which are maybe too low for what you are trying to achieve, but might be a stronger option anyway.
Lower gears take some load off of the input side of things, but put more stresses on the output side. But yours is already pretty well built up in the driveline department, isn't it?

I'm interested too in hearing what others say they prefer about one or the other heavy-duty output shaft options. Whether the DIY version or the fully assembled one in the new housing.

Paul

nvrstuk · Oct 21, 2017

Nothing HD about a D20...the rear output shaft is the BEST mod you can do. Chuck decades ago let me put together a mass buy of 300M output shafts. Benefit was the same length driveline. Gary designed and built the setup that Jim has been selling at W/H for about the same amount of time with the higher spline count but it makes your DS a bit shorter. I was running a ZF/203/D20 at the time and needed all the length I could get.

I swapped in so many D20's and swapped output shafts between the early and late cases and I have NO idea if the later unit is stronger but it doesn't have the snap ring holding the front output shaft brg in place and it isn't as low geared so maybe that adds some strength. Viper would probably know...

All I know is I blew them up left and right and needed something more dependable. Weak points- case can't take much torque, gears are VERY narrow and can't take much torque, shims wear out from the torque, shift rails wear out easily...remember, these were built for use in Broncos and trucks with 28" tall tires, clutch type lockers and mostly 6 cylinder engines or a 302. Not many take this into account.

My .02, if you're spending real money trying to beef a D20 up, save all of it and install a 205 which ONLY WEIGHS 20 more lbs. I've weighed them all... You can clock the 205 up to the frame rails if you want.

Your call. Good luck!

bronconut73 · Oct 21, 2017

/\/\THIS HAS BEEN MY DILEMMA FOR YEARS/\/\

Not the breaking parts thing, lol...

But whether to go 205 or not when I do an OD tranny.

Damn 205 is bullet proof when completely stock.
Dana 20 is so easy to deal with but I'll need expensive adaptors with the OD tranny...
I used to worry about the 205 being in the way of dual exhaust on the drivers side, but I will likely just run one of those cool big ass single exhaust.
Sigh....mo' money....

bknbronco · Oct 21, 2017

if i change trannies ever ill get a completly different t-case......but as long as i still have the 3 speed on the tree ill stick with stock dana 20. Im picking up a used J-shift near me for $100 and just want to know how best to build it to avoid getting heckled by the HEEPS that infest the off road park if i break a easly upgraded part..... It ant gota be bomb prof......just better than stock in every way.

Viperwolf1 · Oct 21, 2017

The only significant weak spot is the rear output shaft, unless you're trying to push 500 ft-lbs or more through it. I think I've only heard of 1 front shaft breaking. I've seen a few cracked cases but those were due to gear failure. The only gears I've seen broken were all tera low.

The advantage of the J front shaft is that it doesn't dig into the end of the front yoke like the T shaft does. When that happens it creates more end play on that shaft. Excessive end play contributes to popping out of gear and abnormal gear wear.

One other area of concern is the cluster gear shaft. That shaft will eventually wear at the bearing contact areas and cause the cluster gear to have excessive movement.

I like to use the T gears when possible because they are about 6% lower. 6% more torque in low range is noticeable. If you want to swap gears be sure to use the sliding gears and the cluster gear from the same case. The other gears are interchangable.

I like the J shift rails better than T shift rails because they have a better pocket to fit the balls and don't allow excess movement of the rail. J rails are also easier to twin stick.

bknbronco · Oct 21, 2017

thanks viper....im gona grab a j-case tomarow for a hundie and will build that for a future swap into my bronco. I just have to buy the shift lever or just twin stick it.

You dont like the 3.15 LOW gears??? too weak? just use the LOW gear from my stock t-shift? Or just not terra brand? Same same here??
https://www.wildhorses4x4.com/produ...er_Case_Gears_Kit/Bronco_Dana20_Transfer_Case I liked this idea of all fresh gears and little lower than stock options....would just need bearings.

Is there a rebuild kit you like to use? I assume most hard part can be used for a very long time and all you replace are seals and bearings? I see some kits have that cluster shaft you spoke of

bknbronco · Oct 21, 2017

so your typical viperbuild would or would not include a HD rear output shaft??
https://www.wildhorses4x4.com/product/Extreme_dana20_Output_systemKit/Bronco_Dana20_Transfer_Case

And i always see your facy cover....for looks mainly or practical strength advantage worth 89 bucks?
https://www.wildhorses4x4.com/product/Billet_Dana20_Transfer_Case_Cover/Bronco_Dana20_Transfer_Case

AZ73 · Oct 21, 2017

I believe the pills on the T rails need to be removed to make it a true twin-stick but this isn't the case with the J. But then again, I believe I'll finish my Bronco again THIS March.....

Where can I get that T-shirt?????

Viperwolf1 · Oct 21, 2017

bknbronco said:
thanks viper....im gona grab a j-case tomarow for a hundie and will build that for a future swap into my bronco. I just have to buy the shift lever or just twin stick it.

You dont like the 3.15 LOW gears??? too weak? just use the LOW gear from my stock t-shift? Or just not terra brand? Same same here??
https://www.wildhorses4x4.com/produ...er_Case_Gears_Kit/Bronco_Dana20_Transfer_Case I liked this idea of all fresh gears and little lower than stock options....would just need bearings.

Is there a rebuild kit you like to use? I assume most hard part can be used for a very long time and all you replace are seals and bearings? I see some kits have that cluster shaft you spoke of

bknbronco said:
so your typical viperbuild would or would not include a HD rear output shaft??
https://www.wildhorses4x4.com/product/Extreme_dana20_Output_systemKit/Bronco_Dana20_Transfer_Case

And i always see your facy cover....for looks mainly or practical strength advantage worth 89 bucks?
https://www.wildhorses4x4.com/product/Billet_Dana20_Transfer_Case_Cover/Bronco_Dana20_Transfer_Case

I'm not saying the tera low gears are bad. Just that I've seen multiple sets of those broken and have never seen a stock gear broken.

I only include aftermarket parts like a HD output or cover if that's what the customer wants. Most of my rebuilds use all stock parts.

This is the rebuild kit I like. https://www.wildhorses4x4.com/produ...d-Kit-for-Dana-20/Bronco_Dana20_Transfer_Case

74 Bronco Billy · Oct 22, 2017

If you decide to go to a NP 205, can that mate right up to a stock C-4? What year and model do I look for? Or do I have to get an over drive tranny to go with the 205?

sanndmann3 · Oct 22, 2017

74 Bronco Billy said:
If you decide to go to a NP 205, can that mate right up to a stock C-4? What year and model do I look for? Or do I have to get an over drive tranny to go with the 205?

Overdrive. The 205 bolts up to a 4R70W like they were made for each other.

sanndmann3 · Oct 22, 2017

nvrstuk said:
Nothing HD about a D20...the rear output shaft is the BEST mod you can do. Chuck decades ago let me put together a mass buy of 300M output shafts. Benefit was the same length driveline. Gary designed and built the setup that Jim has been selling at W/H for about the same amount of time with the higher spline count but it makes your DS a bit shorter. I was running a ZF/203/D20 at the time and needed all the length I could get.

I swapped in so many D20's and swapped output shafts between the early and late cases and I have NO idea if the later unit is stronger but it doesn't have the snap ring holding the front output shaft brg in place and it isn't as low geared so maybe that adds some strength. Viper would probably know...

All I know is I blew them up left and right and needed something more dependable. Weak points- case can't take much torque, gears are VERY narrow and can't take much torque, shims wear out from the torque, shift rails wear out easily...remember, these were built for use in Broncos and trucks with 28" tall tires, clutch type lockers and mostly 6 cylinder engines or a 302. Not many take this into account.

My .02, if you're spending real money trying to beef a D20 up, save all of it and install a 205 which ONLY WEIGHS 20 more lbs. I've weighed them all... You can clock the 205 up to the frame rails if you want.

Your call. Good luck!

Nailed it! Couldn't agree more. I have broke 3 before I moved over to a 205. Just so much beefier. I ran the stock rear output and never had an issue with that. My problem was low range gears failing and idler gears chewing up the bushings then gnawing on the case. I don't think it likes to be spun at high rpm for extended periods of time.

J vs T shift dana 20

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