Gearing and lockers mod

[Mr Twisty]

I am going to be doing some mods this winter on my 78 CJ5 . Below is what I have now as far as drivetrain:
T-150 3 speed Transmission
Model 20 Rear Diff. Gear tario "A" 3.45:1
Dana model 30 Front Diff.
Dana model 20 Transfer Case 2.0:1
AMC 258 i6 / 4.2l inline six
31x10.5 15 mud tires
no lockers.

My plan as of now is the following:

Aussie lockers front and rear
Teraflex low20 Transfer Case kit

This is not a daily driver but I do drive it on the weekends around town and I do my share of wheeln. I thought doing the Transfer Case kit rather than new gears in the axle just because of the time I do drive around town it would be nice to have the original gearing. Looking for everyones thoughts and opinions.

Thanks

 

[BusaDave9]

I would do the Tera Low gearing. Actually I did on my Dana 20 . I think the 2 to 1 Tcase is bit high. This will keep your street gearing unchanged.
This is what I would do if you are unsure about your future mods. You would hate to add lockers front and rear and then later decide you also want lower axle gears.
If you are going to do anything inside your axles think long and hard about lockers, gearing and tire size. You will want to do that job once.

 

[CoreyYoungCj577]

I am going to be doing some mods this winter on my 78 CJ5 . Below is what I have now as far as drivetrain:
T-150 3 speed Transmission
Model 20 Rear Diff. Gear tario "A" 3.45:1
Dana model 30 Front Diff.
Dana model 20 Transfer Case 2.0:1
AMC 258 i6 / 4.2l inline six
31x10.5 15 mud tires
no lockers.

My plan as of now is the following:

Aussie lockers front and rear
Teraflex low20 Transfer Case kit

This is not a daily driver but I do drive it on the weekends around town and I do my share of wheeln. I thought doing the Transfer Case kit rather than new gears in the axle just because of the time I do drive around town it would be nice to have the original gearing. Looking for everyones thoughts and opinions.

Thanks

the only other thing i would do different is buy a T-176

 

[derf]

the only other thing i would do different is buy a T-176

If I went with a T-176 I'd look into a Dana 300 to go with it since the bolt patterns and spline count already match. That and stock the Dana 300 came with a 2.6:1.

As far as the rest of it goes the axle gears are good for that size tire.

 

[Old Dog]

sounds like a good plan to me.

 

[Saddle Tramp]

As you know, the T-150 is your weak link because it has no granny low. (The T-150 is a stout Transmission for the most part other than that.) I think I would look for a T-18 to replace it with. If stock, your 1978 bell housing is drilled for both the CJ & the Ford T-18

Your stock crawl ratio is:

2.99 x 2.03 x 3.45 = 20.9 CRUMMY! (Note: Most 1978 CJs came with a 3.54 gears in the axles)

If you replace the T-150 with a wide ratio T-18 your crawl ratio will be:

6.32 x 2.03 x 3.45 = 44.3 BETTER BUT STILL NOT GOOD

Add the TeraLow kit:

6.32 x 3.15 x 3.45 = 68.7 RESPECTABLE

The next question to ask yourself is what are you going to do with the jeep? Rocks, Mud, Snow, Sand? The reason to ask this question is all of the mediums (mud and sand being closer related) on balance work best with different gearing. Rocks of course = low and slow but both mud and sand sometimes requires that you turn the tires with a little gusto so ultra low gearing is not necessarily the best there. When riding on top of the snow I want no tire spin whatsoever for fear of digging in and low gears once again can be the enemy. Being from Montana I would guess you play in mud & snow in the winter and dried mud in the summer with some rocks in between so the trick is to find the happy medium.

If you leave the differential gearing alone and go for the tranny swap and Tera Low your jeep will still have decent street manors and you will not have to peg the tachometer just to drive down the freeway without getting mowed over by an 18 wheeler. Before I spent any money on lockers I would do the tranny and Transfer Case mods first and see how the gearing feels. Then if you want to drop down to some lower gearing in the pumpkins you can and have not wasted any money on axle work until you know for sure what you need or want.

 

[Mr Twisty]

Thanks everyone so far for your thoughts and opinions. I should have stated that 90% of my wheeling will be rock crawling, not the real extreme stuff you see on videos but more like your average weekend trail rock crawling and climbing. The tranny swap is something that I may consider, liking the the granny gear idea on the T-18 .

Again thanks for the posts and keep them coming.

 

[derf]

Thanks everyone so far for your thoughts and opinions. I should have stated that 90% of my wheeling will be rock crawling, not the real extreme stuff you see on videos but more like your average weekend trail rock crawling and climbing. The tranny swap is something that I may consider, liking the the granny gear idea on the T-18 .

Again thanks for the posts and keep them coming.

If you're going to rock crawl, you will learn to hate that T-150 3 speed manual. It's fine for driving around but you won't be able to get your wheel speed down enough to drive smoothly over anything challenging.

I'd put serious thought into a granny low Transmission with a good low range on the Transfer Case . There are plenty of ways to swap in a T-18 /T-19 or even adapt an NP435 from a Ford or an SM465 from a GM.

 

[Mr Twisty]

If you're going to rock crawl, you will learn to hate that T-150 3 speed manual. It's fine for driving around but you won't be able to get your wheel speed down enough to drive smoothly over anything challenging.

I'd put serious thought into a granny low Transmission with a good low range on the Transfer Case . There are plenty of ways to swap in a T-18 /T-19 or even adapt an NP435 from a Ford or an SM465 from a GM.

That's what I have been fighting, seems I do a whole lot of clutching while crawling, then about the only way to get past the nastier rocks I have to use more speed because I don't have the torque. The granny is starting to look like a real option here.

 

[derf]

That's what I have been fighting, seems I do a whole lot of clutching while crawling, then about the only way to get past the nastier rocks I have to use more speed because I don't have the torque. The granny is starting to look like a real option here.

Before you do anything with the Dana 20 , I would look into your long term plan with the Transmission . Figure out which direction you want to go and then get your hands on the Transmission you want to use. Once you have the Transmission in hand then you know exactly what you're going to want to do with the Transfer Case .

While you're planning, you may run across a great deal on a GM, Dodge or Ford Transmission that won't work easily with your Dana 20 so you'd have to sell it. And you never get out of it what you put into it with the low range kits. While looking for a Jeep T-18 , you could come across a GM SM465/NP205 combination. That would be a pretty solid combination for rock crawling. All you need to make that work is a bellhousing from Advance Adapters, a little fabrication for a Transmission mount and maybe a couple of hydraulic clutch pieces. Oh, and maybe some work on the driveshafts that you can get done for pretty cheap.


In my case, I had a plan to go with my Dana 300 but I got my hands on a 2WD SM465 out of a GM truck with the 35 spline rear output. I went ahead and bought my Atlas that has the mounting kit and input shaft to work with the 2WD Transmission . Had I sunk a lot of money into the Dana 300 , I wouldn't have had the money for the Atlas and I would have had a Transfer Case I couldn't use.

 

[Mr Twisty]

OK everyone, I think I have a plan of attack. I am going to start with the Aussie lockers front and rear. Then I think I'm going for the T-18 tranny and see how things improve, will I need any kind of adapter for the Transfer Case ? If that is not enough crawling torque then I will gor the the Transfer Case low kit. On a side note, I found a T-19 tranny, does anyone have any input on the T-18 vs. the T-19? Again thanks everyone for the input.

 

[CJ]

The T19 is basically the same as a T-18 , but with all synchronized and helical cut gears.

The Borg-Warner T18 & T19 Transmissions - Novak Conversions

 

[Mr Twisty]

The T19 is basically the same as a T-18 , but with all synchronized and helical cut gears.

The Borg-Warner T18 & T19 Transmissions - Novak Conversions

Thanks for the info!

 

[BusaDave9]

If you are planning on putting in a T-18 remember not all T18s are the same. If you have a Jeep with a Dana 20 TCase get a Jeep T-18 . If you have a Dana 300 get a Ford T-18 and you will need an adapter to mate the tranny to the TCase.

Edit: Oh, the T19. What is that out of? I'm sure you will a least need an adapter at the TCase. If you need to adapt the bellhousing end it may not be worth it.

 

[Mr Twisty]

Not sure what the T19 is out of, I found a T-18 out of a Jeep that still has the Dana 20 Transfer Case attached. Am I correct that there were 2 different ratios in the T-18 ; the 6.32 and the 4.02? I am trying to find out if it has the 6.32 because if not I don't want it.

 

[derf]

Not sure what the T19 is out of, I found a T-18 out of a Jeep that still has the Dana 20 Transfer Case attached. Am I correct that there were 2 different ratios in the T-18 ; the 6.32 and the 4.02? I am trying to find out if it has the 6.32 because if not I don't want it.

Make sure that T-18 is out of a CJ. If it came out of a full size Jeep (i.e. Wagoneer, Cherokee or J-truck) it may not fit in the CJ due to a longer input shaft and different bellhousing.

The only sure fire way to tell the difference between the first gear ratios is to shift it into first gear and rotate the input shaft, counting how many full rotations it takes to make the output shaft turn once. 4 turns is the 4.02. Over 6 will be the 6.32.

 

[Saddle Tramp]

The wide ratio CJ T18s were produced from 1977 to 1979 with the close ratio CJ T18s offered from 1971 to1976. If you can find a 1977-1979 CJ T-18 it is as close to a bolt in swap as you are going to get. You do need to make a few mods: (1) lower the skid plate about an inch, (2) move the skid plat back one set of holes on the fame (the holes are already drilled and tapped on a 1978 CJ so no work there) (3) rework the Transmission torque stud mounting plate at the Transmission mount (4) extend the Transfer Case linkage (the T-18 is longer than the T-150 ) (5) Modify the clutch fork slightly. Everything else bolts in from skid plate to pilot bushing on your jeep. Check out this site for more info:

http://www.jeeptech.com/convtrans/cjt18/

The other option is the Ford version of the T-18 . The good news again is that you have both the CJ T-18 and the Ford (butterfly) holes drilled and tapped in your bell housing (assumes stock 1978) as the T-150 is the same Ford pattern. You do need some extra pieces to make this work. First you need a special pilot bushing as the front shaft f the Ford is about ¼ shorter than the CJ and you need an adaptor/shaft change for the rear to mate up to the Dana 20 . Advanced Adaptors & Novak both have them. Try this for a little more info:

http://www.jeeptech.com/convtrans/fordt18/


Finding a wide ratio T19 is a shoot at best. Shaft lengths can be all over the map but you might find a rare Scout T19 that may have the 6.32 1st that will bolt in if you’re lucky.

 

[Mr Twisty]

Well I just ordered my Aussie lockers both front and rear; still trying to find a T-18 but at least now I'm on my way. I would say I'm an average shade tree mechanic but have never dealt with gears; what am I in for with putting these lunch-box lockers in?

 

[Old Dog]

Sorry I've never done a lunch-box.
How about doing a write-up with some pix. when you do it.

 

[Mr Twisty]

Sorry I've never done a lunch-box.
How about doing a write-up with some pix. when you do it.

Will do, gotta start somewhere right. Nothing a weekend and a 12er of cold ones can't take care of I'm sure.