Farm Equipment - Found tach problem on 7060 but have a new problem

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Found tach problem on 7060 but have a new problem

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=188089
Printed Date: 05 Nov 2025 at 5:30pm
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Topic: Found tach problem on 7060 but have a new problem

Posted By: OhKen
Subject: Found tach problem on 7060 but have a new problem
Date Posted: 06 May 2022 at 9:11am

Tach hasn’t worked for several years . Would work sporadically . Kept cleaning alternator plug thought that may be it but no . Checked wire with ohm meter ; showed break somewhere . Well that break was in the harness plug from the cab harness , to the engine harness .
Now my next problem is the engine we put in the tractor is from a N6 . Which required the newer harmonic balancer , which turns out to be smaller diameter on the drive sheaves .
What tach do I need to get the proper reading ?

Replies:

Posted By: DrAllis
Date Posted: 06 May 2022 at 9:24am

I think you need to get the tractor crankshaft pulley on that combine engine. #1. your fan will not be up to correct speed, possibly causing overheating on a hot day. #2. you'll have to come up with a different set of fan belts for length, making it the odd tractor in the fleet.

Posted By: OhKen
Date Posted: 06 May 2022 at 12:34pm

Dr Allis : my other engine that was in the tractor for decades , was a transplant from a 77L2 . The harmonic balancer consisted of 3 equal size sheaves over the hub , that’s it . This engine being from a N6 has a different crank then my L2 .
I now have a harmonic balancer that has 3 sheaves . The 2 inside are slightly smaller than the 3rd sheave . The beyond the sheaves is a large diameter balancer .
Could this of been used in the high out put later 426’s ?
I had not even considered the fan running slower and you are correct !
Was this balancer used in the 8070 ? 4W220 ? Wouldn’t their belts work ?

Posted By: steve(ill)
Date Posted: 06 May 2022 at 12:51pm

Fan speed or alternator speed, or any accessory is a RATIO of the diameter of the old pulley and the new pulley. ........ just for an example, of the OLD pulley was 10 inches diamter and the NEW pulley is 9 inches diameter, then you have changed the speed of your driven accessory 10% SLOWER.... So if it was going 2000 RPM , it is now going 1800 RPM... etc...

That works for the FAN and also the ALTERNATOR. I would consider what Dr said about the fan...... But if you want to change the ALTERNATOR pulley, then it needs to be slightly SMALLER by the ratio of OLD CRANK PULLEY DIA / NEW PULLEY DIA = OLD alternator / NEW alternator pulley.

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Like them all, but love the "B"s.

Posted By: DrAllis
Date Posted: 06 May 2022 at 1:07pm

Your original crank pulley was a steel hub that attached to the crankshaft nose, a steel out shell with the belt grooves in it and a rubber damper sandwiched in-between the steel parts to absorb the pulsations of the engine. The 7060/8050/L2-3 combines were the limit for that type of damper. The engines higher HP than that always had the "fluid" damper, which is the donut you see attached to the front of your pulleys. It has nothing to do with the crankshaft type. It has to do with the HP setting of the engine and all the pulsations/harmonics that are going on.

Posted By: OhKen
Date Posted: 06 May 2022 at 2:36pm

Would the belts , fan off of a 7080 cure my problem?

Posted By: DrAllis
Date Posted: 06 May 2022 at 2:51pm

Don't know. The 7080 had a larger diameter fan and I don't remember is the fan pulley got larger in diameter or the crank pulley smaller in diameter or both. A good parts person could tell you the difference between 7060 and 7080 belt length.

Posted By: OhKen
Date Posted: 06 May 2022 at 4:33pm

My part guy said belts and fan blades were not the same .

Posted By: OhKen
Date Posted: 06 May 2022 at 5:16pm

Pulley sheave from a 7080 is 6-5/8” diameter . Pulley sheave from 7060 is 7-1/2” !