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: 22 Nov 2024 at 12:58am
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
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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
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Replies:
Posted By: DrAllis
Date Posted: 12 Nov 2024 at 7:05pm
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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.
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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
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Posted By: DrAllis
Date Posted: 13 Nov 2024 at 7:27am
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One last thing that I forgot.......160 HP fuel setting versus 127.75 HP fuel setting also stresses the differential more.
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Posted By: SteveM C/IL
Date Posted: 13 Nov 2024 at 11:32am
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Is the 220 stouter in that area?
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Posted By: DrAllis
Date Posted: 13 Nov 2024 at 12:58pm
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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.
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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!
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Posted By: DrAllis
Date Posted: 13 Nov 2024 at 2:26pm
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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.
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Posted By: SteveM C/IL
Date Posted: 13 Nov 2024 at 5:27pm
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My 220 has been relegated to planter and Bush hog so it might be OK at 170.
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Posted By: wildcat2
Date Posted: 14 Nov 2024 at 7:13am
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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.
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Posted By: MrSnerdly
Date Posted: 14 Nov 2024 at 6:37pm
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Does the 210/220 have a different final drive ratio?
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Posted By: DrAllis
Date Posted: 14 Nov 2024 at 7:49pm
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210/220 got one more tooth on the pinion gear (9 teeth to 10 teeth) and the same tooth count on the ring gear. This was for longer service life but sped things up about 10%. The bull gears and bull pinion gears are much wider and larger in diameter and have their ratio geared 10% slower, so all the ground speeds between a D-21 and 210/220 were essentially the same with equal tire diameters and engine RPM. The multi-turboed D-21 pullers usually had a 210/220 ring and pinion installed to make road gear 10% faster. After the engine HP levels grew some more, then custom made overdrive transmissions were the next thing.
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Posted By: injpumpEd
Date Posted: 15 Nov 2024 at 8:17am
The D21 ring & pinion is 4.11:1, and the 210/220 is 3.70:1. Like Dr said, it was kind of a wash though because the final drives put the overall ratios back nearly the same from crank to axle. I am not sure the D21 finals ratio, but I have counted the 210 teeth myself, and the ratio is 6.69:1 on the 210/220. Yes, pullers put the faster 3.70 r&p in a D21 to speed it up some more. Now Mark Gettinger is having new bull pinions made with more teeth and they are cutting down bull gears and putting new teeth on for a faster gearing yet. That's all above my level of pulling though 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!
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Posted By: DrAllis
Date Posted: 15 Nov 2024 at 8:59am
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The very best Super Stock Diesels are turning the rear wheels in the 90+ to 100 MPH speed !! Takes some great big cocoanuts under the hood to do that !!
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Posted By: MrSnerdly
Date Posted: 16 Nov 2024 at 12:03pm
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That is a tremendous final drive reduction on the 210/220. Takes a lot of strain off the ring gear and pinion.
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Posted By: MrSnerdly
Date Posted: 16 Nov 2024 at 12:08pm
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Don't most of the high HP pullers use a truck rear end? I know my cousin did.
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Posted By: PaulB
Date Posted: 16 Nov 2024 at 2:07pm
Yes most of the big HP pullers today are building modifieds and calling them super stockers. Just because you put a tractor hood on something that only has tractor tires on the rear many today think its a super stock tractor even though it doesn't have any parts of the tractor that it's masquerading as. Don't get me wrong I like to see the high HP alcohol and diesel tractors pull, however the "component" tractors are just modifieds with sheetmetal, call them what they are, you can put puppies in the oven, that won't make them biscuits. I also under stand the switch to "component" tractors has been done to improve longevity. I give the guy that can make a "real" tractor live with today's power a lot of credit, there are some out there.
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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY
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