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Dana 20 to Dana 300 Swap

2021 Arizona International Harvester Rendezvous

scoutin1

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I was told that the Dana 300 out of a 1980 Scout II (automatic) will not fit directly onto my non-1980 wide ratio T19. Something to do with the output shaft on the tranny being different on the 1980's. Does anybody know if this is true? I scored a sweet deal on a whole 1980 Scout II with body cancer problems and a solid drive line and I would be disappointed if I couldn't swap the Dana 300 into my '76.:(

On another note the axles in the 1980 are 2.72's! Can anybody tell me why anyone would want that gear ratio? Maybe something to do with smaller tire sizes that were run then? Enquiring minds would like to know! Thanks!:)
 

Baradium

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Gear ratio. Two words: Highway Milage.

T-case, you need the correct bull gear. Not aware of any other differences. Never heard of any. People swap them around all the time.


T-case again: I'd rather have a dana 20 than a 300. 20's are stronger and I'd rather have strength than that slightly lower low range.
 

Mechanos

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Ok, just because it is a 1980 doesn't necessarily mean it's got a D300. There were many 1980's produced with the D20. Verify for certain that you have the D300. One of my 1980's had a 727/D20 and the other had a T19/D300.

If it is a D300, you need to swap the automatic bullgear for a D300/T19 bullgear. Then bolt them together.
 

Baradium

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Originally posted by TORC

Please supply me facts & figures that leads you to believe this.

See the thread that involved that discussion, we went back and forth about the two t-cases before... don't know what the name of the thread is however, maybe someone can chime in? Anyways, those with experience with both cases also agreed.

It has to do with the materials used for the t-cases etc. It has been shown that Dana 20's *are* stronger cases. The *only* reason people like the dana 300 more is the lower low range... well that and the people who assume that it must be stronger because everyone wants them...

What makes you believe that a dana 20 isn't stronger?

So, in my opinion, I don't *believe* that the Dana 20 is stronger, I know it's true. ;)
 

Mike N

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Originally posted by Baradium
20's are stronger and I'd rather have strength than that slightly lower low range.

Why do you say the 300 is weaker than the 20? I would agree that the jeep 300 with the long output shaft is slightly weaker, but the Scout case hasn't caused any problems that I'm aware of.

The differance is not "slight" it's quite a bit. Given the same tranny and gears the 300 makes alot of differance.

T-19 - Transfercase - Rear Ratio
66.32 x 2.03 x 3.73 = 47.85
6.32 x 2.62 x 3.73 =61.76

That's about a 29% improvement in crawl ratio!

scoutin1~
You'll need the correct bullgear, other than that it's a direct bolt in.
 
Last edited:

Mechanos

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Originally posted by Baradium


See the thread that involved that discussion, we went back and forth about the two t-cases before... don't know what the name of the thread is however, maybe someone can chime in? Anyways, those with experience with both cases also agreed.

It has to do with the materials used for the t-cases etc. It has been shown that Dana 20's *are* stronger cases. The *only* reason people like the dana 300 more is the lower low range... well that and the people who assume that it must be stronger because everyone wants them...

What makes you believe that a dana 20 isn't stronger?

So, in my opinion, I don't *believe* that the Dana 20 is stronger, I know it's true. ;)
<rolling eyes while shaking head>
 

BinderZ

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Originally posted by TORC

Please supply me facts & figures that leads you to believe this.

20's have straight cut low-range gears. The low-range gears are the weak link in both cases (in my experience, anyway), and straight cut is stronger than helical. Everything else in both cases is the same.

D20 with Bronco D20 gears and fine splined outputs is as good as it gets behind an IH manual box.
 

Wheeled Scout

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Originally posted by scoutin1
On another note the axles in the 1980 are 2.72's! Can anybody tell me why anyone would want that gear ratio? Maybe something to do with smaller tire sizes that were run then? Enquiring minds would like to know! Thanks!:)

Better gas mileage to help meet EPA requirements, but you're right why would anyone want it.
 

sully0812

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Originally posted by Baradium


So, in my opinion, I don't *believe* that the Dana 20 is stronger, I know it's true. ;)

Well if you know, you must have some facts to back it up.

Other then the straight cut vs. helical cut gears in the low range, I fail to see any difference between the two.

Supposedly the D300 is quieter, but I can't verify that.
 

Baradium

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Originally posted by sully0812


Well if you know, you must have some facts to back it up.

Other then the straight cut vs. helical cut gears in the low range, I fail to see any difference between the two.

Supposedly the D300 is quieter, but I can't verify that.

As mentioned previously... the straight cut vs helical gears do make a difference...

Dana 300 is quieter for the same reason it's weaker...
 

doggone

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The 300's have an aluminum case, or at least part of it is, right? Aluminum is more brittle than steel, and that could shut you down if you got high-centered on the t-case or took a bash from a rock...
I'd still prefer the lower gearing the 300 offers, and just build a tough skidplate :D
 

Mike N

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Incorrect, sorry

Dana 300's do not have an aluminum case....

Only the rear shaft output housing is aluminum. The case is cast iron just like the Dana 20 and Dana 18.
 

Mike N

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Originally posted by Baradium


The *only* reason people like the dana 300 more is the lower low range... well that and the people who assume that it must be stronger because everyone wants them...

So, in my opinion, I don't *believe* that the Dana 20 is stronger, I know it's true. ;)

1. The IH Dana 300 is a direct fit into early Jeep CJ's, hence their popularity.

2. The Dana 300 will accept lower gear set WITH OUT grinding the inside of the case.

I've never meet anyone who "assumed" that the 300 was stronger, but I've meet a bunch of web-wheelers who have opinions on the subject that aren't back up by facts. :eek:
 

Wheeled Scout

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Originally posted by doggone
The 300's have an aluminum case, or at least part of it is, right? Aluminum is more brittle than steel, and that could shut you down if you got high-centered on the t-case or took a bash from a rock...
I'd still prefer the lower gearing the 300 offers, and just build a tough skidplate :D

If you happen to case it you'll most likely brake the adapter if it's an auto or the ears off if it's a manual. In which case it's a tie cause both cases use the same pattern.
 

Aaron L.

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The D300 Advantage

Mike,

I agree with you, and you are on the right track with the gear ratio difference.

>>"The differance is not "slight" it's quite a bit. Given the same tranny and gears the 300 makes alot of differance.

T-19 - Transfercase - Rear Ratio
6.32 x 2 x 3.73 = 47
6.32 x 2.46 x 3.73 = 58

I think that's about 23% lower? "

I thought the D300 had a 2.62/1 low range. The D18 has the 2.46/1 low range, and the D20 has the 2.03/1 as you mentioned. Using 2.62/1 realy brings your point home:

T19wide--T/C--R/P
6.32 x 2.03 x 3.73 = 47.85
6.32 x 2.62 x 3.73 =61.76

That's about a 29% improvement in crawl ratio!

I like the D300 and would use one if it landed at my feet. However, I have a bunch of D20s and will stick with them for now. As to the aluminum output housing and 'weak' output shaft issues, IIRC Advanced Adapters makes upgrade kits for people who are concerned. The fact that you can get a 4.0/1 low range kit for them definately beats out the 3.15/1 (with grinding) available for the D20.

T18wide x D20TerraLow x R/P
6.32 x 3.15 x 4.27 = 85

T18wide x D300TerraLow x R/P
6.32 x 4.0 x 4.27 = 108!!!

That's 27% better crawl ratio!!! Russ Foust has a TerraLow D300 and 4.88s in his rig. This gives that Crazy Farrier a 123.4/1 crawl. I'd have to use Unimog axles (6. something to one) to match his crawl ratio with my D20 (once the Terralow kit get's purchased and installed...) I think I'll just live with the resulting Crawl Ratio Envy (CRE).

Aaron L. (85/1 will be just fine...)
67 800, 196, T90, D27, 4.27 D27/D44T (lousey 29/1 crawl for now)
adlync@earthlink.net
 

Mark Ashford

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The biggest weakness *I* have heard about the D300 (and the d20 for that matter) is the out put shaft breaking... with REAL hard abuse.

So AA and another company (can't remember the name, but its supposed to be better than AA) makes a 32-spline rear out-put kit. I think they make it for the D20 as well.

Don't hear many people blowing the gears out of either a D20 or a D300... with the exception of the aftermarket lower gear sets.



SO, I'll stick with my D300 thank you. I noticed very much the change in ratios... But I think as far as strength goes, yes, there is the *slight* advantage to the D20 for the Strait-Cut low, but reported trace record seems to be they are a wash, and people usually break either the output or bust them off the tranny...


Atlas :D
 

scoutin1

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Mar 14, 2002
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Surrey, BC
QUOTE]Originally posted by Baradium
Gear ratio. Two words: Highway Milage.

T-case, you need the correct bull gear. Not aware of any other differences. Never heard of any. People swap them around all the time.


T-case again: I'd rather have a dana 20 than a 300. 20's are stronger and I'd rather have strength than that slightly lower low range.
[/QUOTE]

Thanks for the information. I am currently tracking down the gear which is a little difficult since the local shops want to tell me what I actually have is not what I know it is. The comments have been: "Dana 20? Are you sure that isn't the front end you're thinking of?" or " Dana never made a Dana 300 transfer case? What kind of truck did you say you have?" Of course it was hard to hear them with their head up their *@#!*#. I will have to pull the transfer case and tranny and get the numbers off the gear and locate a shop that actually has a clue before I do the transfer.

For those who mentioned it I double checked and it is a 300. Thanks for the reminder to measure twice and cut once!

I am absolutely amazed at the amount of great information that everyone has supplied. It confirmed for me that the move to the 300 is the right one as I will be running a Dana 60 in the rear with 3.54's and my budget doesn't allow $2,500 in gear changes front and back to get the lower gearing so the 300 is a nice compromise. I am currently running 32's but will go to 35's with the spring over and while I haven't sat down and done the math I figure that my low range will still be fairly decent. Should I have a long lost relative kick off and bequeath a new set of 4.11's with ARB's to me I will be ecstatic but for now I'll use what I have.

The mileage thing makes sense but it must be hell on hills!

Thanks again folks for all your help!
 

David Lang

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take a look at the performance calculator I have up at http://lang.hm/scout/nph-performance6.cgi

it lets you pick an engine, transmission, gear ratio and tire size and get an idea of what your performance will be like in each gear. along with the ability to do two setups and compare them. to look at the low range multiply your axle gear ratio by your t-case ratio.
 
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