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T5 transmission any good?

MomoJeep

Basic User
Member
City
Seattle
State
WA
I had two catastrophic T5 failures. In both instances, two people in the Scrambler, probably 400 pounds of stuff in the back. Both times happened after sustained interstate driving at around 75mph, probably 3-4 hours running time.

Both times, it just went boom. Both times I was able to force it into 4th gear, drive for about 40 minutes making terrible noises. After that, enough teeth sheared off that it was kinda of quiet. I was able to drive it back home both times using only 4th gear.

Both times 33" tires, 4.10 gears, Mopar MPI on a stock 258.

I finally swapped an AX15 in after 3 T5's in 25,000 miles. About 29,000 on the current AX15 with no issues.

T5 is probably OK on a stock Jeep (tire size, HP, GVWR). But, if you stray too far in any one area you are probably on borrowed time.

I have drove T5's long distances at high speeds in several close to stock Jeeps with no issues.

The AX15 in my red Scrambler made sense for how I drive and use it.

My T5 issues were also probably impacted by the case being wore out in the counter shaft bearing bores, and mainshaft bearing bores. This case finally cracked between the front two bearing bores. T5 case is weak and not alot of meat. No way to improve this design limitation.

That being said, I rebuilt the T5 in my green Scrambler and it seems OK for now (31" tires, 3.31 gears, MPI on a 258 with a bore and cam). This T5 case was perfect and tight. The counter shaft had wear at one of the bearing ends so I installed a used S10 counter shaft (matching tooth counts, better then made in China replacement parts).

My stock 1985 Spring Special CJ7 has a T5 and it is fine.

Depends on how you use/abuse/modify the Jeep. And, if you like pulling/rebuilding T5's once or twice a year!!!!
Is is safe to say it's high speed driving on the freeway that is the *reason* these boxes wear out? Or is it high-torque situations that wear them down which then makes them likely to fail once they are on the freeway?
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
I've always have manuals. I have no experience off-roading with an automatic. Pro's and Cons? I'm sure this is a big debate..
 
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Chamba

Not obsessed: focused.
Member
SOA Member
City
Vero Beach
State
FL
Very much personal preference. I like the manual for off road. I grew up wheeling in the mountains, snow and rocks with manuals and love the feel of knowing exactly what my rig is doing. I feel disconnected and bored when i wheel with a slush box.

But others think it makes them superwheelers because the hydraulic pump and torque converter help keep things smooth instead of their left foot. Which is why.....it's all personal preference.
 

GreatCJ8

Charter Member
Gold Member
City
Lynchburg
State
VA
What should I expect for highway driving:
Tf999, 410s, 33"?

Can't wait to feel how this drives with fuel injection, hei, auto, 33s, RV cam
 

93_Fummins

CJ-8 Member
City
Edmond
State
OK
Is there a transmission with a Granny Gear that is not one of these clunky "truck" transmissions? Maybe a T19?
T19 is no different than a T18....still very long throw. The "best" shifting transmission with decent gearing, based solely on my personal experience having driven many manuals, is the ZF S5-47 5-speed wide ratio found behind Ferd 3/4 ton gassers in the '90s. The ZF's are far from a "car" transmission in terms of feel, but are the quickest shifting of the "granny gear" truck boxes that I have driven personally. Again, just my personal opinion.

Another option would be to run the Toyota variant of the Aisin transmission; the R151F found in land cruisers and hilux trucks. Similar in architecture to the AX15, but with a 4.31 1st gear ratio, and direct adaptation to the venerable Toyota crawl boxes. I briefly considered this route with my 8, until I noted the "toy tax" that goes with those kind of pieces.

There's also the NSG370 Jeep 6-speed, with 4.46 1st gear...
 

Chamba

Not obsessed: focused.
Member
SOA Member
City
Vero Beach
State
FL
The land cruiser transmission is the H55F for the 5 speed or the H41 for the granny low 4 speed. Either one will only mate to a Toyota transfer case: the H55F will only mate to the latter Toyota split case. Both are phenomenal boxes and the split transfer is bomb proof. HOWEVER, it requires an offset rear diff so would require the land cruiser axle.

Both gear boxes are non-US (the US version is 4 speed only and is called the H42. It is not a grant low).

I find the AX15 very similar to the H55F as far as comfort, though the first gear is not as low. I rarely used my first gear in my H55F.

The NV4500 is a great compromise: a bit truck- like but also has a granny low version.
 

ag4ever

Average Nut
Silver Member
Lifetime Member
City
Richmond
State
TX
NV4500 is huge and heavy though. I believe it is 100 lbs heavier than an ax-15.

Still a long throw, slow shifting truck transmission.

Also has the toy tax, when you can find one.
 

John N

Addicted....Ex-SOA VP
BENEFACTOR
Gold Member
Lifetime Member
SOA Member
City
Rockville
State
VA
I've always have manuals. I have no experience off-roading with an automatic. Pro's and Cons? I'm sure this is a big debate..
My reasoning…I have 2 feet, hence 2 pedals. It works for me.
 

MomoJeep

Basic User
Member
City
Seattle
State
WA
I think an AX15 with a 4:1 Tcase might be the way to go!? That get's me a dependable, strong, light and easy-shifting box combined with the super low gearing I would get with a granny-gear truck box.. Sound right!?
 

CJ7Pilot

18436572
BENEFACTOR
Gold Member
Lifetime Member
SOA Member
City
Yuba City
State
CA
I think an AX15 with a 4:1 Tcase might be the way to go!? That get's me a dependable, strong, light and easy-shifting box combined with the super low gearing I would get with a granny-gear truck box.. Sound right!?
That's how I had my CJ7 set up, and I thought it was a great combination! :thumbsup:
 

spankrjs

Scrambler Junkie
Lifetime Member
SOA Member
City
Biloxi
State
MS
My red Scrambler currently has a JDM AX15 with 4:1 first gear, and 4:1 gears in the Dana 300.

My JDM AX15 ratios pretty much match up with the original Jeep T5 ratios.

The 4:1 Dana 300 is nice when needed, but it does limit you in some instances (i.e. need wheel speed to climb a muddy hill). Even 2nd and 3rd gears with 4:1 in the transfer case are too low sometimes. With the transmission in 4th gear, Dana 300 in low range, I am at the same ratio as 1st gear high range.

I like the 4:1 low range 90% of the time, so I am happy with it. The low speed control is great. With an automatic transmission, the 4:1 low range is not needed 90% of the time. The "lack of direct connection" in 1st gear with an automatic transmission gives you low speed control.

The tan Scrambler that I sold had a 700R4 and stock Dana 300. Most of the time, I never felt the need to add 4:1 to the transfer case. With how I use(d) both Scramblers, and how they were both set up (33" tires, 4.10 diff gears).

Depending on tire size/axle ratio's, overdrive might not even be needed. I daily drove my 1978 CJ-7 for over 10 years (304 V8, T18, stock Dana 20, 3.54 axle gears, 33" tires). Never felt it needed overdrive. The T18 was not bad behind the 304 (more power then the 258), but it would probably suck behind a 258 for street driving (2nd gear is deep, the jump in ratio from 2 to 3 is pretty large, so the lack of power would be more evident, and you are basically driving a 3 speed). Not terrible, but probably would not be "fun".

IMO, the T-18/stock Dana 20 low range was more capable then my current JDM AX15/4:1 Dana 300. I had a super deep granny gear, but could easily shift to 2nd/3rd gear and have all the wheel speed/vehicle speed I needed. Just depends on terrain.

The AX15 is nicer to drive on the street compared to the T18. With the AX15, you have 5 gears to keep the 258 in its powerband. With a T18, only 3 widely spaced gears. The T18 has long throws, true, but a stock AX15 isn't exactly a "short throw" transmission. An upgraded shift tower can make the AX15 feel like a sports car, if desired.

Depending on the model NV4500, not all are terrible. We have an older 1996 Chevy 1-ton flat bed at work. It has the 6.5 turbo diesel and an NV4500, with granny gear. I spent all day Sunday driving this truck (hauling 3-4 yards of dirt at a time), and it shifts fine, much better then any of the older "granny gear" 4 speeds. I am not an "expert" on NV4500's, but the one in this truck has short tight shifts, and 1st gear is synchronized (no need to double clutch to get it into 1st, or reverse for that matter).

Just depends on what you are used to driving.

I almost wonder if I would be happier with an NV4500 and stock low range? I could upgrade my red Scrambler and keep the AX15 for my green Scrambler (if ever needed) :crazy:
 

spankrjs

Scrambler Junkie
Lifetime Member
SOA Member
City
Biloxi
State
MS
Picture of my currently install 4.3 1st gear "JDM AX15" I bought from Novak back in 2014:

IMAG2828_zpsb542ce16-1.jpg



Red Scrambler T5 #1 failure, post #1097, 10,000 miles on it (counter shaft bearing journal wear, front bearing):



Red Scrambler T5 #2 failure, post #1128 (catastrophic failure, input shaft and counter gear):



Red Scrambler T5 #3 failure, post #201(catastrophic failure, input shaft and counter gear):



Green Scrambler T5 Issues Post #200 (125,000 miles, counter shaft bearing journal wear, rear bearing):

 

Chamba

Not obsessed: focused.
Member
SOA Member
City
Vero Beach
State
FL
I didn't know about that JDM box. I wish I had. I got mine from Novak in 2019. It's their HD version but just the standard first as far as I can tell. Still, for my needs it's just about perfect.....
 

ag4ever

Average Nut
Silver Member
Lifetime Member
City
Richmond
State
TX
If I was looking for a JDM AX-15 I would contact Marlin Crawler.

If I had a Jeep AX-15 and wanted the lower gear set I would also contact Marlin Crawler.

But I would also expect to turn my pockets inside out in the process.
 
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