Farm Equipment - D21 Differential

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D21 Differential

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=204137
Printed Date: 14 Nov 2024 at 9:39am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: D21 Differential

Posted By: PDehring
Subject: D21 Differential
Date Posted: 12 Nov 2024 at 11:56am

I have a D21 that doesn't want to turn, even with using the brakes. I'm suspecting the differential has become locked. I was wondering if anyone has experienced this and what the cause was.

I haven't torn into it yet but was looking for any info before I do.

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1937 M Crawler, 1963 D21, 1964 D21, 1965 D12 SIII, 1970 220, 1976 185

Replies:

Posted By: DrAllis
Date Posted: 12 Nov 2024 at 7:05pm

Been there done that. Low transmission/rear end oil levels (all one compartment) is for sure the death of a differential located that high in the drive line. A tractor used for moldboard plowing would have the highest failure rate possibility. Four new matching radial tires across the back and a lot of short turning would be stressful. A tractor that weighed more than 13K would also place the differential under more pressure. I remember a customer who once got one buried in the mud and rocked it back and forth and back and forth while jamming on the brakes side to side. Soon afterwards the differential was toast. What's the history of the tractor ??? I've always looked back to a D-17 or WD-45 and think of the hundreds upon thousands of hours some of those tractors had on a moldboard plow and NEVER had any differential issues.

Posted By: PDehring
Date Posted: 13 Nov 2024 at 7:19am

Thanks Dr. I'm not sure on the history of it, I got it last year after it had been sitting in a barn for 20+ years. It does have 24.5x32s that are half loaded. The rear end does have enough oil (plenty on the dipstick) but who knows what the tractor was put through in the last 60 years.

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1937 M Crawler, 1963 D21, 1964 D21, 1965 D12 SIII, 1970 220, 1976 185

Posted By: DrAllis
Date Posted: 13 Nov 2024 at 7:27am

One last thing that I forgot.......160 HP fuel setting versus 127.75 HP fuel setting also stresses the differential more.

Posted By: SteveM C/IL
Date Posted: 13 Nov 2024 at 11:32am

Is the 220 stouter in that area?

Posted By: DrAllis
Date Posted: 13 Nov 2024 at 12:58pm

210-220's used the same differential. They had a larger bearing on the ring gear side of the diff where the D-21 was same bearing on both sides. 210-220's were way heavier in the final drive/bull gear and axle size area. The wheelbase was even 4 or 5 inches longer because of the larger diameter bull and bull pinion gears.

Posted By: injpumpEd
Date Posted: 13 Nov 2024 at 1:53pm

Not to argue with Dr, he's forgotten more than I'll ever know. But, the 210 rearend I just rebuilt a few months ago had the same diff carrier bearings on both sides, and looking at parts books, the D21 also used the same cups and cones as 210 & 220. As to the op, guessing you have a galled up differential assembly, with a permanent diff lock lol!

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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!

Posted By: DrAllis
Date Posted: 13 Nov 2024 at 2:26pm

I might have confused myself with the 4-pinion's on 190's and 200's. I know they had a bigger bearing on the right side, and for some reason I thought the 210/220 series did too.

Posted By: SteveM C/IL
Date Posted: 13 Nov 2024 at 5:27pm

My 220 has been relegated to planter and Bush hog so it might be OK at 170.

Posted By: wildcat2
Date Posted: 14 Nov 2024 at 7:13am

You might want to drain the oil out and remove the large plate covering the ring , pinion, and bull gears. When I did this found the pinion gear with broken teeth and the bull gear starting to flake. Ended up replacing ring and pinion with one from a 220 and reversing the rear axles. This tractor had been turned up to 180 hp. Good luck.