What transmission?

[jveesart]

Ok guys I’m fairly new to the Jeep world and got an 81 Scramber that needs some attention. Right now it’s a 151 with an SR4 and 2.73 gears sitting on 29” tires. I want to do a lift and move up to 33’s. So here’s my question. I have a 350 330hp motor sitting on my shop floor that’s begging to go in the scrambler. What transmission would be the best fit? Gears 4.10? Not my daily driver just something to goof off in and head to the mountains which are about 3 hours away so 65 mph on highway would be good. Moderate mountain trails no rock crawling. Thanks in advance for any help.

 

[walkerhoundvm]

Based on a bunch of reading, help on the forum, etc. I think you'll want either a t176 or a stronger 5spd like the ax15 or nv3550. Check out the grim jeeper site to get an idea of rpms. The t176 will probably have you at a pretty high rpm for that speed, tire size and gearing. 3hrs drive would be a long time at that rpm. The 5spds with overdrive would be easier on the ears and the tranny.

I think the gear selection is good. I'm going with 3.73s @ 33" for a few reasons. They'll be on the low side, but I'll be hitting 70mph at 2100 rpms or so.

 

[Rosco1974]

You want auto or manual? If I were putting in a GM motor I would stay GM on the trans for compatibility/simplicity. Some autos get wide and can cause problems with the Dana 300.

 

[Spieg]

With a GM engine, I'd be tempted to stick with GM trans and t-case just to cut down on the number of adapters. Are you thinking manual trans or automatic?

 

[jveesart]

You want auto or manual? If I were putting in a GM motor I would stay GM on the trans for compatibility/simplicity. Some autos get wide and can cause problems with the Dana 300.

Definitely want a manual.

 

[Rosco1974]

SM465 would be a common choice. Unless you run a NP205 your gonna need an adapter. The SM465 to Dana 300 is short. With engine/trans adapters you ban run about any trans. It's all about the factory combo vs. $$$.

 

[jveesart]

SM465 would be a common choice. Unless you run a NP205 your gonna need an adapter. The SM465 to Dana 300 is short. With engine/trans adapters you ban run about any trans. It's all about the factory combo vs. $$$.

How is the SM 465 on the highway? From what I’ve found it’s more of a 3 speed with a granny gear. I know there are a lot of options and I don’t want to say that money doesn’t matter but it’s always cheaper to do it right the first time.

 

[FLCJ8]

As mentioned, go here http://www.grimmjeeper.com/gears.html and play with different setups.
It has pull down menus for most transmissions and t-cases, so you can see what each one offers and you don't need to know the gearing to fill the form.
You can compare two side by side.

 

[93_Fummins]

With a GM engine, I would lean toward an NV4500, if you can find one. In my mind, it's the end-all manual transmission: beefy enough to grow into one-tons, round 6 pattern for lots of t-case options, granny low available in early models with still a decent low in later models, and OD for the highway. They are one of the more expensive manual options due to demand, but rightfully so. Next choice would be AX15/NV3550 due to easily adapting to the D300, being stout enough for calm to mild V8 power, and having OD for cruising.

As for gears, I would probably lean toward 3.73 for 33" with a 4-speed, and 4.10 with 33" with an OD.

 

[AtomicYJ]

I have an '83 K10 I drive everyday with a 350 and an SM465. I only use first when towing or four wheeling. I love it. Its indestructible. I have 33" BFG All Terrains and 3.73 gears. I can easily run 70 at around 2600 rpms all day and i get 11-13 mpg. Its a great transmission

 

[jveesart]

Ok so it looks like it’s narrowed down to an SM465 and AX15. I can get a brand new AX15 for about $1,500 and a used SM465 for about $600. Honestly the difference in price isn’t enough to make my decision. Why should I choose one over the other? Again thank you all for your help.

 

[AtomicYJ]

Sm465 has a 6.55:1 first gear for off roading and towing. The transmission weighs about 175 lbs and is damn near indestructible. Very easy to get parts for, if you go on a chevy truck forum you can find one for much less than $600. I just got a spare this weekend for free and my time to pick it up.

 

[93_Fummins]

Ok so it looks like it’s narrowed down to an SM465 and AX15. I can get a brand new AX15 for about $1,500 and a used SM465 for about $600. Honestly the difference in price isn’t enough to make my decision. Why should I choose one over the other? Again thank you all for your help.

Desired usage should tip that scale. The SM465 will take a beating all day every day, so if you plan on wheeling hard or working the 8 hard pulling things, it's a given. The AX15 is tough, but not big iron 4-speed tough. If you plan to drive more and wheel gently, the AX15 would be a good go-to. The AX15 will also adapt to the D300 with only a clocking ring and possible shift bracket trimming, and give you the benefit of a lower low range than the likely applied NP205 of the SM465 application. For crawling the SM465/NP205 will be 6.55 x 1.96 = 12.84, and the AX15/D300 will be 3.83 x 2.62 = 10.03....so not a huge benefit either way, but the OD of the AX15 will let you have a lower axle gear to make up for it.

 

[Kane]

Here is my opinion for a small block motor and highway driving on 33's. SM465 mated to a Dana 300 with a 4.1:1 gearset and 3.55 gears in the axles. This will give you a decent highway RPM at around 2300 but also the iron clad strength of the SM465 with a nice low range of about 93-1. Now those older small blocks like to have all their ignition mechanical advance timing in by around 2100-2200 so this will be a nice sweet spot for economy because the vacuum advance can do it's job better.

 

[jveesart]

Thank you everyone. I think I’ll go look for an SM465

 

[Rosco1974]

Unless you stumble across something like this: https://classifieds.ksl.com/listing/53028729

$1500. 1992 chevy NV4500 with the sought after 6.34 first gear and new rebuild kit. (New bearings and syncros). Transmission works good but was going to rebuild everything all at once for piece of mind. Brand new Advanced adapter jeep 4.0 bell housing. Dana 300 transfer case that has a brand new 32 spline input shaft.

Shipping would probably kill you. He might still have the GM bell housing. Could sell the 4.0L bell housing and your Dana 300 to offset the cost.

 

[CJ7Pilot]

That's a steal!

I spent almost that much just rebuilding and adapting my SM465 and D300.

If they'll strap it to a crate and ship it by truck, shipping costs shouldn't be that bad.

If I'd have found something like this six months ago, I'd have dropped everything and gone this route.

 

[walkerhoundvm]

Thank you everyone. I think I’ll go look for an SM465

A challenger appears!

https://yuma.craigslist.org/pts/d/sm465-dana-300-adapter/6644203044.html

 

[CJ7Pilot]

That's a fair deal too, if you're confident of the rebuild.

 

[ag4ever]

If your jeep was a factory 4 cyl, you probably have 4.10 gears. Assuming you still have stock axles.