Transfer case compatablity?

C

Crum351

New member
I have a 1973 Scout II 4x4 with a 304 v8 and a 3 speed manual transmission. I would like to switch out the manual transmission with an automatic transmission that is out of a 1975 Scout II 4x4 with a 345 v8. The automatic transmission is missing the transfer case. Will the transfer case from the 3 speed manual trans match up with the automatic transmission? Do I need to change the input gear in the transfer case that mates up with out output gear from the automatic transmission?

Thanks,

jarrod
 
Not only is the spline count/tooth count amongst various d20 bull gears (input gear) different, so is the helix angle of both the bull gear and the mating intermediate gear set.

We've posted about this "pitch angle" difference many times right here in this sub-forum.

Edit: in the following paragraph I made a mistake in posting spicer part numbers, the numbers in red are the corrected items:

The bull gear for the 727 output shaft 23 spline was made in only a single pitch angle (17.5*, spicer p/n 18-8-56) and must be mated with a spicer p/n 18-5-16 Intermediate gear. It's tooth count is 26.

The bull gear currently installed on the 3 speed trans could have a pitch angle of either 20* or 17.5*, that is dependent upon the part number stamped on the gear itself.

Post the part numbers on both the bull gear you have along with the intermediate gear currently in the d20 and we will tell you what your compatibility is.
 
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You will also need to swap over the flexplate and hub spacer from the 345 in place of the flywheel you have on the 304 now, and you'll need the starter shim to correctly orient the starter gear with the auto flexplate. You May encounter some drive shaft length differences as well. Do you have access to all the parts from the auto-equipped Scout as well? Pedal assembly, shifter, shifter cable & linkage, kickdown rod & linkage, etc etc.?
 
That is the problem with this old crap, over the last forty years folks have swapped around transfer cases, transmissions, bull gears and all the guts of a d18 or d20 indiscriminately because others told 'em it "didn't matter, they are all the same". But we deal with repeated gear and transfer case failure, extreme noise, transmission output shaft bearing failure and even full transfer case lockup due to mixing and matching incorrect parts quite often around here!

The ihon forum deals in verified factual information, not "I thinks" or "it might", unlike most other technical forums, this is our customer service/technical support outreach for our customers.

Fortunately spicer did a very good job of positively identifying each part in their component assemblies and it's easy to verify part number matches and compatibility.
 
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Thank you for all of the information. I do have everthing from the from the 345 minus the transfercase, drivelines, and foot pedel assembly.

The numbers stamped on the bull gear (output gear) on the 727 transmission are 18-8-56 and b3n44k3. It has a tooth count of 26. This number doesn't match 18-8-33? Is this still the same

the transfer case is currently in the Scout. I will post the numbers for that in about a week or two when I get the chance to pull it.

If it turns out I need to change out the gear on the transfer case does IH Parts America sell that item? If not any suggestions as too where to find one?

Agian, thank you very much for the help.

Jarrod
 
Please review my previous post regarding the spicer part numbers, I wrote wrong information!

I was in the midst of responding to another member's email regarding converting a Bronco d20 to use behind a torqueflite. When I did the cut-and-paste of the part numbers/descriptions, I mixed up his information with your's. So I scruued up both responses!! Sorry! I've now corrected both of my scruu-ups! Time for the assisted living center is gettin' closer and closer....

So...18-8-56 is the correct and only bull gear for the IH 727 output shaft. And...it will only work with a 18-5-16 intermediate gear in the d20. With careful observation and a flashlight and mirror, you should be able to read the spicer p/n on the intermediate gear in your current transfer case once it's on the bench.

If you have both pitch angle intermediate gears on the bench side-by-side, you can see the difference in the angle. But looking at one or the other by themselves, I can't determine what the angle actually is without a part number!

If you attempt to "mesh" the incorrect gear pair, they will go together (kinda). The system will transmit power. But it will be noisy as hell and soon one or the other items will fail!

I have n=3 spicer 18-5-16 intermediate gears at my location if Jeff has no used ones at ihon hq. On a scale of 1>10, one of 'em is a 5 (ok for trail/off-road only), the other two are 7.

Sorry again for tossing out the wrong info!
 
Thanks. I am just glad that don't have to find two gears! I was worried that I got the short end of the stick on that automatic trans.

I will let you know if I need a gear.
 
I finally got the transfer case out of the 1973 Scout. The part numbers are hard to see inside the transfer case, but I think it says 18-5-16 then it is followed by what appears to be p2 14. I also looked at the output gear on the three speed and it reads 18-5-55.

So it appears I am in luck from what I could read.

Thanks very much for all the help.
 
crum351 said:
I finally got the transfer case out of the 1973 Scout. The part numbers are hard to see inside the transfer case, but I think it says 18-5-16 then it is followed by what appears to be p2 14. I also looked at the output gear on the three speed and it reads 18-5-55.

So it appears I am in luck from what I could read.

Thanks very much for all the help.
Click to expand...

To confirm...

The intermediate gear with spicer p/n 18-5-16 is a 17.5* pitch angle and a tooth count of 34 and 20.

The three speed manual tranny spicer p/n 18-5-55 bull gear you found is also a 17.5* pitch with a tooth count of 26 and spline count of 6.

The bull gear for the tf 727/t-407 transmission is going to be spicer p/n 18-8-56, has a pitch angle of 17.5* with a tooth count of 26 and a spline count of 23.

So you win this round! Good work and you have learned stuff!
 
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