670T front crank seal
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=209868
Printed Date: 22 Mar 2026 at 12:38pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 670T front crank seal
Posted By: Northern Hoser
Subject: 670T front crank seal
Date Posted: 26 Jan 2026 at 1:47pm
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Hi all, Rebuild of my 8030 went pretty well, all except the front seal (74036340) developed a leak within the first hours and were going to have to go back in. Is there anything unique about this seal? pics I'm seeing kind of look different than what I'd expect; also seeing what look like a simple rubber seal or one with felt in it. Depends on the manufacturer. Which one would be the best to put back in there? Pretty sure it was an AGCO supplied seal, or one from the kit which was a Reliance Kit Shop that did the rebuild is going to pull and replace the seal just wondering if there's any tips or tricks with it maybe I could pass on. It could also be a leak really close to the seal area we'll have to rule out first, but oil is coming out behind the balancer somewhere. Thanks, Matt
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Replies:
Posted By: DrAllis
Date Posted: 26 Jan 2026 at 5:42pm
| Your seal installer must match the O.D. 0f the seal and can't be too thick. Always use some light oil on the inside of the seal and on the nose of the crank. Seal must be pulled/pushed in until it hits the stop wall machined in the timing cover. |
Posted By: HudCo
Date Posted: 26 Jan 2026 at 6:19pm
| best to have a install tool to push those crankshft seals in instead of driving in with a seal driver , with a sael driver i allways worrey about messing up the spring inside the lip of the seal just my opinion . even if i have to take time to make one |
Posted By: 8070nc
Date Posted: 26 Jan 2026 at 6:42pm
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Maybe im wrong but i remmember rebuilding a 7040 that it was a seal that the part on the crank turned with the crank and it sealed inside itself. Hard to explain but i remember it being more robust than a regular seal ------------- 1984 80780 1957 D14 DES 300 with 25000 engine 616 tractor |
Posted By: Northern Hoser
Date Posted: 26 Jan 2026 at 6:45pm
Ah that explains the look of the one I'm seeing, I've seen wheel seals like that before. |
8070nc wrote:Posted By: Northern Hoser
Date Posted: 26 Jan 2026 at 6:47pm
Much appreciated! |
Posted By: SteveM C/IL
Date Posted: 26 Jan 2026 at 6:51pm
| 8070 is correct at least on 8000 series...the inner part slides on crank and turns inside outer part much like a wheel seal on a semi. When doing on assembled engine should have a spacer of sorts that fits seal and push seal on/in with a plate and bolt threaded into nose. An all thread and nut works well. Doing this by hand you can tell when you hit bottom. |
Posted By: SteveM C/IL
Date Posted: 26 Jan 2026 at 6:57pm
| Make sure the pan gasket is not the leak. |
Posted By: DrAllis
Date Posted: 26 Jan 2026 at 7:21pm
| That style of seal is often referred to as a "unitized" seal or a "cartridge type" seal. |
Posted By: Northern Hoser
Date Posted: 28 Jan 2026 at 2:40pm
 So here's the right side, has oil above the oil pan on the cover, hard to tell exactly where it's coming from but I'll double check the pan before getting in there |
Posted By: DrAllis
Date Posted: 28 Jan 2026 at 3:30pm
| Cracked cover ....?? |
Posted By: Northern Hoser
Date Posted: 28 Jan 2026 at 5:04pm
I'm wondering that myself. I gotta have a better look but didn't look like it was wet at the bottom of the seal and there isn't any oil being slung out by the balancer. |
Posted By: SteveM C/IL
Date Posted: 29 Jan 2026 at 10:25am
| Get everything clean and dry (Brake Clean)and watch closely. A fan can move the oil around making the leak appear to be somewhere it's not. |
Posted By: Sids
Date Posted: 29 Jan 2026 at 5:52pm
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I have done this a time or two but not saying it is the best. Remove crankshaft pulley and clean the cover and all area very well. Install pulley not too tight, put belts on and run engine a little while while intermittently holding your hand over the breather hose, not too much. This will of course make some crank case pressure. Remove dampner and inspect. You can also Run a little with dampner off for a better look. Make a pusher for the seal that you can pull in with the dampner bolt. Lastly I always push the inner part of the seal a small amount back with a small screwdriver so it is not tight against the metal frame of the seal just the way I have done for years. |
Posted By: Northern Hoser
Date Posted: 31 Jan 2026 at 2:58pm
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So after cleaning things up and checking again, the windage from the pulley is moving the oil around a bit, but it is indeed coming from the seal and then running across the cover where it's seen in the pic. I'll update when we get in there a finally fix it. Matt |