LS swap manual transmission questions.

The7t7

Member
So I’m close to to starting my D110 manual LS build on a 1991 2 door (3 door?) And have been creeping on both defender sites for year or so. I have a couple questions about my manual transmission choices. RW Engineering offers t-case (I will go with an Ashcroft HD 1.2 LT230) adapters for both NV4500 and AX15. Axis offers an adapter for the Tremec 4050. My preference is for the AX15 since it probably shifts better and has a taller first gear for daily driving (this will be more an adventure rig vs a trail rig). However, I spoke to Novak about the torque rating on the AX15 and they said the AX15 was rated to only 300 lb-ft whereas the other 2 are in the 400+ range, which is more suitable for strong LS (I will probably go with a crate 6.2 If I have to go with the heavier nv4500 or maybe build a gen iv 5.3 if I have the time).

Has anyone here done a swap with the AX15 or the Tremec 4050? Any advice or opinions on which to choose? I know a couple members have used the NV450 and are happy with that. One of the NVs versions has first gear in the 5. range vs other versions and Tremec being over 6. Also has anyone used the short shifter kit for the NV and would that appropriate and help the truck shift better as a daily? Last question is can I get by with my LT77 tunnel on any of those transmissions? Thanks!
 

Napalm00

Technical Excellence Contributor
Well I haven't done this swap I can tell you that the TR 4050 is going to shift way more smooth than an AX15 will.

If shift quality is what you're worried about from best to worst it is TR 4050, AX15, any NV trans.

If durability is what you're worried about from best to worst (in stock form) it is TR 4050, nv, then ax


The NV transmissions while extremely durable are an older design and are what I would consider "agricultural" I put them in the same class of shift quality as a rebuilt LT77 or r380.


That being said locally here there's a gentleman with a Corvette LS sitting in front of a beefed up AX15. He hasn't had any transmission issues.
 

sgo70

Member
Does it have to be a manual? I've done a Gen 4 5.3 into my JK and I'm currently putting a Gen 5 5.3 in my Defender 110 as well I have a Gen 4 6.0 in my truck, all are running the 6L80. At first I wasn't a big fan of the automatics and wanted the tapshift so I could at least pretend. After driving around for a few months in my JK I found out I didn't even care about the tapshift anymore, although I am putting it on my Defender for offroad control, I found with the low gearing of the 6L80 I didn't need it. Daily driving in traffic is so much nicer. I've been running them for the last 7 or 8 years without any problems, they're cheap, they can handle over 500ft/lbs torque and you'll only need one adapter to the LT230 from Nick.

Just mount a spring loaded clutch pedal and use the tapshift haha. Just another opinion, not trying to tell you what you should do.

Sean
 

The7t7

Member
Does it have to be a manual
I have seriously considered the auto and know it’s the more common swap for good reasons. Part of the appeal to me of the defender and classic vehicles in general is the fun factor. The manual with the v8 would be more fun for me. Although I want it to be capable of being an easy daily driver, it won’t actually be my only daily. I have an automatic Jeep Gladiator Mojave that serves that purpose. I was going to have the Jeep be the manual and the 110 be the auto but it took 6 months for the new desert rated Mojave to be produced and the first batch of trucks at the dealers were auto’s. I admit I got a little impatient and settled for the auto.
 
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pmatusov

Technical Excellence Contributor
AX15 is a solid box - people use it in fairly high horsepower and torque applications.
The one I had in a Cherokee was okay to shift - not the smoothest by any means, but I lived with it without noticing any inconveniences.
 

sgo70

Member
I get it, I wouldn't buy an automatic Ferrari either.

If you look through the Jeep forums a bunch of guys have done the manuals but I can't remember which one. Motech has probably done hundreds and Robbie has some good videos on You-tube.

Sean
 

The7t7

Member
If shift quality is what you're worried about from best to worst it is TR 4050, AX15, any NV trans.
That’s what I figured. BD makes a short shifter for the Dodge nv4500 and it’s described as making the nv4500 more fun to “row the gears with authority”. I don’t think it would fit on the earlier NVs because of the built in shifter housing and not sure if it’s Dodge only. It also puts the knob a little further back and to the left which I would think would help it clear the dash and future AC.
I will look more into a “built” AX15. Novak said they only sell the stock ones. Still hoping some one who has used either option will chime in about fitment and tunnel clearance. Thanks everyone!
 

Napalm00

Technical Excellence Contributor
If you gonna spend all this coin why compromise on something that's obviously not rated for the application ?
 

The7t7

Member
If you gonna spend all this coin why compromise on something that's obviously not rated for the application ?
I’m assuming you mean the AX15 choice. To me it’s unclear of what the real world rating would be. In my searches I’ve seen anywhere from 300 to 380 lb-ft for that transmission. A bunch of those posts are really old. I was also getting a vague response from Novak transmissions. When I called them the person I spoke to couldn’t find it and then came up with 300 number by saying it’s the same as the NV3500, which he could look up. He also said that they sell the stock rated transmission and didn’t really answer when I asked a bout a heavier duty version. But on Novak’s own website description they tout their AX15s as having the latest upgraded parts and cast cover, which I would think makes this the HD version referred to in some older post from around 2008. Also, I believe torque rating may be vehicle weight dependent. On Tremec’s distributer (https://shiftsst.com/tremec-transmissions#TR4050) site the 4050 is rate at 425 but with a 15klb? GVWR. Since I’m interested in the taller first gear of the AX15, I was hoping I to find a “real world” rating for it. If it’s rated at say 380 but if the “at GVWR” part is much higher than a defender’s (AX15 I think was originally a Toyota transmission an could have been put in some of their heavier land cruisers or industrial vehicles?) then the “real world” rating might be enough for a lighter Defender with a 450lb-ft LS. I’m obviously no expert here and have only done a few engine/trans swaps that were all original equipment options etc, thus the post here. The LS chatter on both forums has died down a bit most everything has been covered. I am
Leaning towards the NV4500 for the reason you mentioned but it is 100lbs heavier. I’ve only seen one reference to an TR4050 in a defender but that was behind an R2.8 and still under construction in the latest post. Tunnel clearance/ease of install would also be a small factor in the decision.
 

The7t7

Member
Her is some more info in case someone needs it in the future. AX15 with latest updates should probably be good to 350-380 ft lbs and maybe been dynoed to 450. That’s what I have been able to piece together from various posts on Jeep forums, though that’s not official by any means. I haven’t been able to find anything on a Tremec 4050 behind an LS in a defender. I have an email into Chad at Quick Draw about drivability and tunnel clearance of that trans behind the R2.8 but have not heard back. Finally I found this site https://www.blocklayer.com/rpm-gear.aspx for figuring speeds with various gearing. Attached is a photo of my calculation using the NV4500, Chevy gearing, 1.22 LT230 ratio and 33” tire. I’ll probably throw this thread over to d-source to see if I can get any more comments about a Tremec4050 LS set up.
06A4D69D-4C91-476F-8D4E-D30B04F41DB8.png
 
Has anyone installed the tremec 4050 with an LS and LT230 or know of someone who has successfully done this? If so, which adapter and did it require moving the engine mounts?
 

rocky

Well-known member
Has anyone installed the tremec 4050 with an LS and LT230 or know of someone who has successfully done this? If so, which adapter and did it require moving the engine mounts?

Pretty sure the tremec to LT230 has been done with the Cummins conversions. Take a look over there.
 
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