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4:1 Dana 300...?

CJ7Pilot

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Just kicking around a project for this fall....

So, my Scrambler drivetrain consists of a 350 chevy small block, a Muncie M20 4-speed transmission (2.5:1 first gear), a stock (2.5:1) Dana 300 transfer case and stock 4:10 axles.

Initially, I had it in mind to swap the transmission for an SM465 (6.5:1 first gear), and keep the D300 as-is... however, the Muncie is kind of retro-cool, and REALLY fun to drive!

I'd like to keep the Muncie 4-speed, so for off-road gears, I'm thinking about installing a 4:1 kit in my D300.

10 years ago, I built a Terra-Low 4:1 D300 for my CJ7, with an AX15 5-speed (3.8:1 first gear), and 4:10 axles, and was very happy with the results!

For my type of driving though, hunting, fishing, camping... unlikely that I'll ever tackle the Rubicon... I'm not sure a 4:1 transfer case is really necessary, even with my Muncie transmission...!

I'll probably do it anyway though... because I like to tinker.... :crazy:

If anyone has a 4:1 D300 lying around, I'd probably be interested.
 

certifiablejeep

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I have it in my off road rig... 6.32 granny low and the 4:1 and I don't even have the axles swapped in yet (4.56), so there are 3.31's in there at the moment.
All in all, I love it, no complaints.

Going in the Scrambler is the same setup
6.32 granny Low, 4:1 kit in the d300, 4.56 ARB's in the Dana 44... will be a nice slow crawler.

cb
 

CJ7Pilot

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Drive Train Refresh

After almost 2 years, I'm finally getting to this project!

I need to do it now, because I'm replacing my engine, and I want everything new or rebuilt when I put it back together.

In the interest of minimizing down time, I picked up a spare Dana 300, and am rebuilding it now. I decided to stick with the original gearing for now, and I can rebuild my other one with 4:1 gears later on, if I think it's necessary.

I was planning on rebuilding my existing transmission, the Muncie M20 I mentioned before. BUT... I just found the right deal on an SM465, with a bell housing and flywheel! I think the SM465 will be a better transmission for my needs. The M20 is fun, but it's not really very practical as a Jeep transmission.

This will allow me to assemble the engine/transmission/transfer case completely ahead of time, and down time for the swap should be minimal.

Once I'm finished with the Dana 300, I'll open up the SM465 and see how it looks.

I'm trying to decide which adapter I want to use. The Novak adapter replaces the main shaft with one that has the correct output splines, and the AA adapter uses a spud shaft that slips on the existing output shaft (after cutting down a little bit). The spud shaft is supported by it's own bearing, so it should be plenty sturdy. Both adapters are about the same price.

My choice will probably depend on the amount of work I think the transmission needs before I run it. If I have to rebuild the main shaft anyway, I'll go with the Novak kit. If all the synchros and bushings look good, I'll probably go with the AA kit.

Any opinions?:shrug:
 

CJ7Pilot

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Here's the current state of my Dana 300:

D300 - 1.jpg

:cheers:
 
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gr8dain

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Glad you got a spare. Looking at that on my workbench would depress me as I know that I would not have it done soon enough for my liking.
 

spankrjs

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I have 4:1 in my red Scrambler with an AX15, I love it for the trails, but some times it sucks. For your uses, hunting, camping, light off road use, I think it will be overkill, and you will find yourself in 4th gear while in low range.

If you are swapping in the 465 with compound low first, I would keep the stock Dana 300 low range gears :twocents: You are gaining your "4:1 reduction" while in first gear in the transmission.

When I am on technical parts of trails I love my 4:1 Dana 300, but a lot of times I find myself in 4th gear in the transmission moving down the trails once I get past the hard stuff. Even at Moab, 4:1 was too much 90% of the time :twocents:

I would rather have the deep first gear of a granny gear transmission with stock low range transfer case gears. I had a CJ-7 with a T-18/stock Dana 20. Off road, it was more capable then my AX15/4:1 Dana 300 Scrambler, especially on mud/sand/loose dirt hill climbing. I had the super deep low first gear to crawl, but when I needed wheel speed/momentum I could shift to second gear.

I much prefer the AX15 for on road use, over drive is really nice when driving cross country :rotfl: I am happy with my red Scrambler, but some times I know the stock low rang gearing would be more practical :twocents:
 

CJ7Pilot

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Good advice! :cheers:

I put an AX15 in my CJ7, and added 4:1 gears to the D300... but I sold it before I got a chance to wheel it. Just from playing around on flat ground though, I always suspected the 4:1 might be too low for my needs.

I'm excited about getting this put together. For better or for worse, it's going to drive like a completely different Jeep!
 

CJ7Pilot

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I have it in my off road rig... 6.32 granny low and the 4:1 and I don't even have the axles swapped in yet (4.56), so there are 3.31's in there at the moment.
All in all, I love it, no complaints.

Going in the Scrambler is the same setup
6.32 granny Low, 4:1 kit in the d300, 4.56 ARB's in the Dana 44... will be a nice slow crawler.

cb

With a 118:1 crawl ratio, you'll be able to hop out, take a leak, and hop back in without ever taking it out of gear! :eek:
 

CJ7Pilot

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Well, bummer... I was hoping I could re-use the essentials.

I know people don't like the strap-style yokes, but I've never actually seen a failure:

yoke - 1.jpg

That must have been interesting!
 

tower210

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I just put a 4:1 kit in my 300....to go with my new AX-15. My 373 is prolly too low for the 4.0 (and my plan to bump to 285/75's or 255/85's)....but the 4:1 should get me by for a while... Highway likely won't be fun....

I'll post back after I've driven.
 

CJ7Pilot

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I think you'll be pretty happy with that combo! 3.73 is certainly not too low, especially with overdrive. :cheers:
 

Randyzzz

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My 4:1 case with the 5.3 and 4L60E- seems way too low. I never use low range for the stuff I do.
 

CJ7Pilot

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No turning back now....

crate - 1.jpg

crate - 2.jpg

The SM465 in the background of the first photo is enormous! It's about 100 lbs heavier than my M20, it hangs down a lot more, and the side flange "may" interfere with the front driveshaft, if I clock the transfer case.

Is this really what I want for a hunting/fishing/camping Jeep, or is this more of a rock-crawling setup?

My thinking is, rebuilding and adapting the SM465 to the Dana 300 costs almost as much as putting 4:1 gears in the Dana 300.

Maybe I'd be happier with the quick shifting M20 and a 4:1 transfer case....

Maybe I don't even need 4:1 gears!

Right now (stay with me here, because I think it's actually relevant), with a roughly 2.6:1 first gear, and a roughly 2.6:1 low range... my high range first gear is roughly the same as my low range 4th gear! This gives me a pretty good spread, with very little overlap, but my crawl ratio is still only 27.8:1 (with 4:10:1 diffs).

That feels pretty slow on flat ground, but I haven't tried to climb anything.

With a 4:1 low range, my crawl ratio would be 42.4:1... now that's pretty respectable! But... I'm afraid that at trail speeds, I'd be shifting a lot between high and low....

If I went with the SM465, and stock transfer case gears, my crawl ratio would be 67:1... could my axles even take that kind of torque, if I gave it the gas?

I'm torn between the daily drivablilty of the M20 vs the off road indestructability of the SM465.

I've only got a few days to figure this out, before I start ordering parts.

Your input would be MOST welcome! :cheers:
 

CJ7Pilot

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My 4:1 case with the 5.3 and 4L60E- seems way too low. I never use low range for the stuff I do.

Yeah, automatics change everything... unfortunately I can't make that part of this swap. I could probably find a reasonably priced T350, but that would mean a trip to the CARB referee. One step at a time.

One of the most active wheelers I know runs a CJ7/258/TF999/D300(4:1)/3.07:1 axles/32" tires, and he's unstoppable! The 4:1 transfer case really made a difference for him, because of his high axle gearing.

I think, based on what's been shared so far, that I'll just reassemble the D300 with stock gears for now.

I'll give some more thought to the transmission. Heck, if a nice AX15 fell in my lap right now, both Muncies would be out of the running! :thumbsup:
 

93_Fummins

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Heck, if a nice AX15 fell in my lap right now, both Muncies would be out of the running! :thumbsup:

Do to some life and build scope changes, I have an AX15 with AA GM bellhousing and external hydro kit sitting in my garage looking for a new owner. The bell is the goofy early one with the fork arm on the passenger side (which I do not know if clears a passenger drop driveline or not). It needs synchros put in it, which I also have, but haven't gotten around to doing. I also have a T176 with the GM bell from behind an Iron Duke... I'm joining the dark side and going LS with auto in my 8 so the wifey can drive it as well (she hates manuals unfortunately). Just throwing things out there seeing as you are making great progress and will likely be enjoying your 8 far before I'm enjoying mine. Shoot me a PM if interested...
 

sdsupilot

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If it were my decision, I would use the stock 300 gearing and the SM465. You would have a great crawl ratio in 4 Low. Also, second in the SM465 will be lower than first in the muncie (3.58 vs 2.5). The 465 would basically be a 3 speed trans on the street, as 1st is super low. I think this would be a great combo with a 350 and 4.10 gearing.
 

CJ7Pilot

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Fummins, thank you so much for offering the AX15 option! Even though I didn't get back to you, I've been kicking it around all week. :cheers:

However, I think I'm going to commit to the SM465.

SDSU, I was on the fence, and your advice tipped me toward the SM465. :wave:

Anyhow, today I took the top cover off to have a look inside:

sm465 - 1.jpg

It looks pretty clean, but the synchros are completely worn out (not broken, though). Third gear is almost 1/8" out of alignment due to a dished retaining ring, which I kind of expected.

Also, the reverse gear has lots of grinding wear (as does the reverse idler):

sm465 - 1 (1).jpg

So, I'm going to go with the Novak conversion and rebuild kit, which includes a new output shaft (to fit the Dana 300), and a 3rd-4th counter shaft bushing (to eliminate the dished retaining ring problem).

QUESTION: Should I bother getting a new reverse gear and idler? The old gears are pretty chewed up on the ends... but the gear faces themselves look really good!

It doesn't seem like the rounded tooth ends would really affect the function of the reverse gear..

I've just about got the t-case buttoned up, so I'll be tearing in to the transmission pretty soon. :thumbsup:
 
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CJ7Pilot

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I got the D300 pretty well finished today. I just need to let some gasket maker set up, and then fill it with oil... I hope it doesn't leak!

d300 - 1.jpg

This little gizmo covers the shift shaft seals, and aligns the shifter thingie....

d300 - 2.jpg

The underside of this gizmo has plenty of space... almost enough space for another seal... but not quite.

d300 - 3.jpg

I'm thinking there should be a felt wiper seal in this space. This is a sliding shaft, not a rotating shaft. This pocket was filled with mud when I took it apart... and an oil soaked felt wiper would provide plenty of extra protection against dust and dirt.

I can't seem to find 5/8x1-1/8x3/16 felt seals anywhere, so I'm going to cut some of my own.

Any thoughts? :shrug:
 
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