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T5 transmission any good?

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
So my 83 Scrambler came with a stock T-5. It seized up on me, on the freeway doing 65mph, scared the crap out of me and could've caused a wreck as the rear end went into fishtails.

I know they are considered relatively weak. After my previous experience I'm spooked. If I buy a Jeep from the mid-eighties that has a T-5 in it, (say relatively stock drivetrain, like 258, 35" tires, 4.1 gears) can I rely on it?
 

ScramblerGuy77

Basic User
Gold Member
City
Winterset
State
IA
So my 83 Scrambler came with a stock T-5. It seized up on me, on the freeway doing 65mph, scared the crap out of me and could've caused a wreck as the rear end went into fishtails.

I know they are considered relatively weak. After my previous experience I'm spooked. If I buy a Jeep from the mid-eighties that has a T-5 in it, (say relatively stock drivetrain, like 258, 35" tires, 4.1 gears) can I rely on it?
Do your self a favor and buy a NV 3550 or AX 15 that is already rebuilt. Advance Adapter is your friend. Spend the money correctly the first time.
 

Chamba

Not obsessed: focused.
Member
City
Vero Beach
State
FL
My HD AX15 from Novak is a really nice transmission, shifts great and doesn't seem to mind the 300 horses I'm putting through it..... at least not yet.
 

HWB3

Legacy Registered User
Silver Member
City
St. Louis
State
Mo
I have a freshly rebuilt T4 rolling 33’s. It still shifts like a T4. If you can find someone who knows how to rebuild it, that is your first issue. Second, T4-5 were never built to roll those big tires and especially if you’re geared lower than maybe 373.
 

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
Do your self a favor and buy a NV 3550 or AX 15 that is already rebuilt. Advance Adapter is your friend. Spend the money correctly the first time.
I have an AX in my Scambler. So far so good, although the reverse gear doesn't synchro very well. Do others have that issue?

Also, I had my eye on SM420/465 instead of the T5. Anyone have thoughts on those?
 

Chamba

Not obsessed: focused.
Member
City
Vero Beach
State
FL
The SM420 is a truck transmission: strong, but shifts like mixing concrete with a spade.

I find double clutching my reverse helps. When you come out of a forward gear, go to neutral and the release the clutch for a second. Then depress the clutch again and go into reverse.
 

wm69

Scrambler Junkie
Silver Member
Lifetime Member
City
God's Country
State
AR
I like the T176. I don't drive on the highway all that much and it easily handles 60-65 without overrevving the engine.

I have an SM465 in my GMC pickup. The T176 is much easier to shift/more pleasant to drive.
 

CJ7Pilot

18436572
BENEFACTOR
Gold Member
Lifetime Member
SOA Member
City
Yuba City
State
CA
I went with the SM465, and it's definitely a truck transmission. I really wish I'd have gone with an AX15... but I put so much time and money into rebuilding and adapting the SM465, that I'm going to be stubborn about keeping it, and driving it. ;)
 

ScramblerGuy77

Basic User
Gold Member
City
Winterset
State
IA
I have an AX in my Scambler. So far so good, although the reverse gear doesn't synchro very well. Do others have that issue?

Also, I had my eye on SM420/465 instead of the T5. Anyone have thoughts on those?
My First Jeep a 1999 TJ did that.
 

Randyzzz

Blown Budget
BENEFACTOR
Gold Member
Lifetime Member
SOA Member
City
Redmond
State
OR
I have an AX in my Scambler. So far so good, although the reverse gear doesn't synchro very well. Do others have that issue?

Also, I had my eye on SM420/465 instead of the T5. Anyone have thoughts on those?
IIRC, the 420 does not have a synchronized 1st gear. The 465 is a more modern version, I’ve driven plenty of them and they are definitely truck transmissions. Heck for stout but shift like a truck.
 

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
I went with the SM465, and it's definitely a truck transmission. I really wish I'd have gone with an AX15... but I put so much time and money into rebuilding and adapting the SM465, that I'm going to be stubborn about keeping it, and driving it. ;)
I had a similar experience, I had a Jeep T18 w/granny in my garage, I thought it was going to be the best option. However, I noticed it was HUGE and very HEAVY compared to the AX15. So I actually put in the AX15, much easier to fit it in. It seems the T!8 or the SM's would be the choice for a true Rock Crawler. But that's not what I'm building. Pretty happy with AX15 so far.
 

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
IIRC, the 420 does not have a synchronized 1st gear. The 465 is a more modern version, I’ve driven plenty of them and they are definitely truck transmissions. Heck for stout but shift like a truck.
Can you describe "shift like a truck"... You mean real clunky? Hard to actually shift from one gear to another?
 

Chamba

Not obsessed: focused.
Member
City
Vero Beach
State
FL
Not so much 'hard to shift' but rather 'requires deliberate action '. The shifter carries engine vibrations as if you were holding on to the valve cover and you need to shift it directly and precisely to prevent gear clash.

Reverse on the SM420 definitely requires double clutching and down shifting will often require double clutching. Speed shifting is also not something you'd be doing much of with the 420.
 

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
I'd like to refine my question here. My T5 failed catastrophically, suddenly seizing up at freeway speed with NO WARNING. There was no obvious noise or vibration to tip me off that it was going to fail.

So my question is, isn't that highly unusually? For those of you that have had transmission failure, how did it go down? Aren't there usually warning signs, enough to make you check to see if the gear oil has metal in it?
 

spankrjs

Scrambler Junkie
Lifetime Member
SOA Member
City
Biloxi
State
MS
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!!!!
 

Randyzzz

Blown Budget
BENEFACTOR
Gold Member
Lifetime Member
SOA Member
City
Redmond
State
OR
Can you describe "shift like a truck"... You mean real clunky? Hard to actually shift from one gear to another?
Chamba described it well. My best description is with a T5 or AX15 you do a 2-3 shift and it’s a fairly smooth diagonal motion. On a 465/420 it feels like 3 distinct motions- up,over, up. You get used to it but there’s no quick shifting.
 

MomoJeep

Basic User
Silver Member
City
Seattle
State
WA
Chamba described it well. My best description is with a T5 or AX15 you do a 2-3 shift and it’s a fairly smooth diagonal motion. On a 465/420 it feels like 3 distinct motions- up,over, up. You get used to it but there’s no quick shifting.
Sounds like the right box for dedicated rock crawlers!
 
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