Drivetrain suggestions

Can't decide what I want to do.
I have several options.....

I have 2 Dauntless 225's for my engines
I have 1 T15 and 2 T18 transmissions available.
I have 1 big hole D18 and also 1 D20.
I have 1 AA tapered intermediate shaft to use in one of my builds. (to quiet down some noise)
I have 1 Tera Low 4 gear set. (I suppose it could possibly be upgraded to a 5 gear set if need be.)
I have 1 good Warn 29 tooth overdrive
I have 1 Tera low bowl gear for the O.D.

Should I...

1) Build a D18 with 2.46 gears and use the tapered intermediate bearings.
This would be used with standard Warn 25% O.D. and a T15.
Crawl ratio of 36 to1 with T15 and 4.89 differential

2) Build a D18 with 2.46 gears and use the tapered intermediate bearings.
This would be used with standard Warn 25% O.D. and a T18.
Crawl ratio of 76 to1 with T18 and 4.89 differential.

3) Build a D18 with 3.15 gears and use the tapered intermediate bearings.
This would be used with special bowl gear for Warn O.D. and a T15.
Crawl ratio of 46 to 1 with T15 and 4.89 differential.

4) Build a D18 with 3.15 gears and use the tapered intermediate bearings.
This would be used with special bowl gear for Warn O.D. and a T18.
Crawl ratio of 98 to 1 with T18 and 4.89 differential

3) Build a D20 with 3.15 gears and use the traditional intermediate bearings.
This would be mated to a low geared T18.
Crawl ratio of 74 to 1 with 3.73 differential.

I hear stories about the D18 being extremely loud with Tera Low gear sets.
I'm thinking along lines of a versatile daily driver and not a crawler.

 

option 2 using the Dana 20 case in place of the D18 case, using the standard D18 gear ratio. Can't see dealing with low gears in the transfer case if you're not gonna crawl it.

 

For a dd, not a crawler, I'd use the T-15 & od combo.
The three speed will be nicer to drive for daily use and you'll have enough low range for general off road use.
I've been quite disappointed with the AA Tcase conversion...I think mine is just as loud as before, maybe more so.

 

Option 2 for me, but Ive never tried driving with a T18.
So maybe option 1 if you don't need the better crawl.

 

If it were me (and it's going to be just that with my '79 CJ5) I would go with the T18 and one of the D18. You can have the same overall reduction as the 3 speed if you never use first in the t18. But when you need it, you can more than double the overall low gear ratio.

My '79 with The T150 and a Dana 20 and 3.54 gears has a 21.5:1 low range and that's not enough. I can swap 4.56 in (which I have setup in another set of housings) and get 28.3:1. But the T18 with it's Dana 300 gets you 28:1 in SECOND gear. In first it's 58.8:1 keeping the 3.54's which would still just cruise down the highway.

I am really close to selling the 4.56 and keeping the 3.54 and the T18 is what can make that happen. So, T18 and the D18 with the tapered shaft and don't look back. Sell the expensive 4:1 gears and use that money to pay for the T18 conversion kit.

 

All viable options and it just depends what you want to use it for. I would be going for #4 but just because I get into a lot of rock. If you aren't going to be rock crawling, #4 would be silly for just about all other use. For general use, including some wood hauling in rough country, I think #2 would be best. Being you have all the parts, we all know the 4 speeds are going to likely last way longer than the T15. And I actually had very good results running the AA tapered roller shaft. At least in my situation, there was very noticeably less noise.

 

Wheelie,
I don't have the rare special gear required to build a 2.46 ratio D20.
Those special 2.46 gears are sourced from early Broncos.
I see no gearing advantage to installing 2.46 when I can put 3.16 gears in a D20
The 4 gear set Tera Low is for a D18.
If I want to put Tera Low in the D20 I will need to get another gear. (5 gear set)

colojeepguy,
I really want to go with the smooth shifting T15 but I am barely content with a typical stock standard Willys having a 37/1 crawl ratio.
Never heard any prior complaints about the AA tapered shafts.
My main objective with the AA shaft is to reduce some of the inherent D18 highway noise.
The D20 (AKA Silent Type transfer case) would be a much better solution for the noise.
After all; that's why the "Silent Type" transfer case was invented.

68BuickV6,
Option #2 yields a very reasonable crawl ratio and eliminates and Tera Low growling problems.
The only drawback is the slower shifting and extra weight of the T18

Glenn,
Again the meager 36/1 crawl ratio is my only complaint. Otherwise it's near perfect.

Mike C,
Yes I once owned a new 1976 CJ-5.
The T150 with 3.54 differential and D20 was definitely to high of crawl ratio for my needs.
No way I'll run another D20 with meager 2.03 reduction ratio.
I see 3 drawbacks with using the T18 .
It's much heavier weight.
Slower shifting and has a less desire-able shift pattern making it much harder to rock the jeep fore and aft.

Duffer,
Yes the 98/1 crawl ratio is extremely tempting but
I would then have a real crawler and all the increased concerns that goes with that territory.
In truth I would probably be content with a low crawl ratio about 55/1 to 75 to 1.
The typical Willys 37/1 crawl ratio is pretty insufficient at times.

 

Yes, but you could miss the aroma of the burning clutch disc.

 

The complete factory Dana 18 gear set will go in a JeeP Dana 20 case and the 20 cases are said to be stronger. I am assuming you are dealing with all Jeep parts in your inventory. And by doing this, you can retain your off set rear axle. Going another route with the 20 case may leave you in need of a centered rear axle, perhaps, depending on how you proceed.

I may be misunderstanding your position. If I am, my apology for muddying the water.

http://www.earlycj5.net/forums/show...-transfer-case&highlight=Dana+gears+dana+case

 

Wheelie,
Yes my D18 is a "Big Hole Case", essentially the same as the D20 case.
I have no problem building the Transfer case to be tough enough.
I have plenty of good parts like AA transfer case girdles and such.
I also have plenty of good axles to use.
I have both; the offset flanged or the center flanged rear axle.
The only way I'll run a centered carrier rear axle is if I decide to install the D20.
Because the D20 does not normally accept an O.D. unit I would put 3.73 gears in the center flanged axle housing.
That will give me the correct RPM at cruising speed.
Otherwise If I build a D18 I would most certainly use an O.D. unit and 4.89 differential gears.
I have plenty of 5.38 differential gears but those with O.D. gives me too slow of cruise speed without excess engine RPM

 

Maybe I'm biased, owning a couple of T-15 Jeeps... but compared to the T-18, it's a much easier shifter. Rowing a T-18 in city traffic gets pretty old, but not so much with the B-W 3-speed. If you expect to use this Jeep to commute in city traffic, the T-15 is a lot more appealing. JMO - the D18 is noisy, regardless of its condition. So is the T-18. But if I had the Tera gears, I'd use them and the fresh T-15. Choice of the D18 or D20 depends on which axles you have. Recall that Jeep sold the D20 as the "silent" transfer case.

I wonder if the tapered bearings will make much difference in noise - I thought that mostly came from the constant gear mesh of the intermediate gear, not bearing noise. I thought that gear noise was mostly dependent on the helix angle, and the less angle the more whine. The D18 intermediate has to be strong enough to power front and rear, thus minimal angle and a lot of noise (I presume). Same with the T-18 - heavy duty gears are both strong and noisy. The Muncie 4-speeds are a case in point: http://www.5speeds.com/muncie3.htm This is why chain drive cases are used exclusively today, and none of the modern cases have offset rear axles.

Considered an automatic? You need less reduction then, but it's a different two-footed style of trail driving. TH350/NP241C?

 

timgr,
Yeah I hear ya , I agree the T15 will be ideal excepting the crawl ratio.

True the helix angle is the main concern.
That's exactly why Jeep built the 2.46 ratio transfer cases to replace the 2.43 ratio cases.
The 2.46 was Jeep's/ Dana's effort to reduce the transfer case noise. (circa 1954)
Dana's next effort was the D20 (AKA silent type case) which came out in 1962

I'm just going on what some guy told me over the phone.
But he claimed his T15 / Tera Low / O.D. and 5.38 combination was perfect except...
The Tera Low bowl gear was much louder than a standard 2.46 bowl gear.
Herm never really gave me an answer on that one.

I really don't mind shifting and just would not consider an automatic.
With T15 it's advantageous to be able to go from 1st and then into reverse and back.
That's an important and effective maneuver when hung up in deep mud ruts.

 

The AA Tcase conversion in mine is pretty quiet under load, but howls like a banshee under decel. I suspect that the gears, although they looked to be in good shape, had some wear to them and the roller bearings have changed their position in relation to each other enough to produce the howl. I probably should have found a new intermediate gear to use for the conversion.
One other point to consider...I value my Warn overdrive just as much for its gear splitting ability as for the reduction in highway RPM's. I'd much rather live with a noisy D18 & have what is essentially a six (or eight) speed tranmission.

 

colojeepguy,
Yeah I have been running the Warn 25% in all my jeeps since the early 1980's.
It's become a staple with the D18 jeeps and is mandatory in my opinion.
D18 with Warn 25% O.D. likely the best argument against using a D20.
But certainly not as efficient nor as quiet as the straight through transfer case.

 

#2 would be my choice.

 

jpflat2a,
Thank Jim.
Sounds like a very reliable choice.
Like Ford used to say:
Dependability is job #1

 

#2.

The versatility of the T-18 cancels out numerous other downsides, such as using the Tera low gears, the too-low 37-1 crawl ratio, etc. I think you'll get used to going up and down thru the gears.

Just try to get that T-18 tight and quiet. Though I haven't put one in a jeep, I've had several truck 4 speeds in PU trucks. It's a pleasure to use one that has had a fresh, properly done rebuild.

All these years, you've never had a 4 speed or a V6 in a jeep, correct? Go with the different stuff this time. I think you'll be glad you did.

 

Glenn,
Certainly not needing a dedicated rock crawler but I do occasionally get into demanding situations.
For example .. when crossing deep log skidder / tractor ruts in the mud I find the 37/1 ratio about twice too fast for comfort.
76 to 1 crawl ratio should fully satisfy all my realistic needs.
Bouldering is another thing and besides I just can't afford tearing up a jeep on the rocks.
I think you #2 voters are seeing it for what it is.
Basic, no nonsense, no weird modifications and uses 100% genuine Jeep parts.

gunner,
Your right, I've been driving stock CJ-3B's exclusively since 1984.
I'm way overdue for a change and a major upgrade.

Yes # 2 (T18 /2.46 / O.D with 4.89 differential) has been my basic goal for several years now.
The others options all just seem have certain specific appeal.

I've driven SM 420's when I was a teenager and I still recall them as being sloppy shifters.
I have acquired several T98's and T18's over the past 10 years.
From what I can tell I fully expect the T18 to have a tighter shift pattern than the SM 420.

Your right the T18 makes up for nearly all the faults of the other builds and only adds a little extra weight / length / height.
Beside I actually like to shift.
Everything I've ever owned was a stick shift.
I turned against auto trannies at a very early age while watching my father get frustrated working on a Powerglide.
I saw him happily work on his SM 420's as a kid but he hated to work on that Powerglide and I have never once forgot that.