Looking for 6602 Tach Part Number: Please look at your Tach

[swiss]

For those of you with a 6602 can somebody look at your Tachometer and get me the part numbers from the front of the tach please.

Correct NSN Part Number from TM
The correct NSN number for the 6602 is 6680-00-620-2325,

Current NSN Part Number
I have the following part number installed in the truck which looks like a multifuel and different tach. The multifuel tach is a 1/2 drive based tach. I am not sure if the gasser tach is a direct drive tach and is not stated in the manuals that I have been able to find yet.

Current Tach Part Numbers
MS35916-2 on front of Tach
NSN: 6680-00-825-2076

We are trying to troubleshoot vibration in the truck at 2000 RPM. The vibration is most evident in the hood and dash panel. The vibration is not evident in the engine or the transmission but more like it is originating from the flywheel or clutch assembly. This vibration will rattle the truck bad, but it is not really felt in the engine or the transmission shifter. This vibration happens when at a standstill with the clutch in or out when RPM's go over 2000.

Step number one is to determine the engine RPM to get a baseline of where our problem may originate.

 

[vtdeucedriver]

I never thought that the tach would be different. I will note the PN when I get down there this week.

 

[swiss]

VT we are still trying to sort this out but it seems from the research that the Tachs are different. The Gasser is driven off the distributor and the Multifuel is driven from the front timing cover. An interesting note is that the 2.5 ton gassers did not have a tach.

If you can get the PN's off the front that would be great. There is a pn on the top of the dial and 2 numbers on the bottom.

 

[5tondeuce]

Here is a pic of mine 1953 M41 R6602. Hope this helps

 

[vtdeucedriver]

VT we are still trying to sort this out but it seems from the research that the Tachs are different. The Gasser is driven off the distributor and the Multifuel is driven from the front timing cover. An interesting note is that the 2.5 ton gassers did not have a tach.

If you can get the PN's off the front that would be great. There is a pn on the top of the dial and 2 numbers on the bottom.

Correct on all 3 items but other than cable lengith unless you put a few bends on the gasser to use a multi tach cable to use up the maybe 10" difference, I would think and they look like the same ends. I am headed there wed, I will write the numbers down.

BTW, I could use a cable

 

[73m819]

Here is a pic of mine 1953 M41 R6602. Hope this helps

5t, What rpm on this tack, does your governor kick in, what is your shift point,

 

[5tondeuce]

I'm not sure Ron i have only ever driven this truck around the yard at low rpm...sorry

 

[73m819]

Correct on all 3 items but other than cable lengith unless you put a few bends on the gasser to use a multi tach cable to use up the maybe 10" difference, I would think and they look like the same ends. I am headed there wed, I will write the numbers down.

BTW, I could use a cable

The ends are the same, the tack is different.

We are getting good pull at 2000 (like it was 2600/2800, 2100 gives us shake, rattle., I sorta rolled though a stop sign in 4th, speed way down, 900 rpm, thought I would need to drop to 3rd, BUT got on throttle, the truck pulled like it was at 1500, I have been told that this shake is a sign of over-rev.

5t,
That tack that you showed has the same MS number that ours has, looks like your tack was replaced because it does not match the dash, if that is the case, you MAY have the wrong tack also, we are still doing research on the tack issue, there seems to be at least TWO NSN numbers so far, one for the 6602 tack and one for our existing tack, but NO "this nsn supersedes this nsn"

 

[vtdeucedriver]

Interesting thread!!! I will get down there to check it out.

 

[swiss]

It gets a bit more interesting. So I pulled the dash out the other day. There is a pn on the tach that is maybe 4 digits. I could not find any numbers in the TM or G-744 that matched this short number and did not record. I may have to go back and get that number. I am curious what number you have now on your Tach. VT?

What RPM does your governer kick in? We have the governer disconnected at the moment given a whole new set of problems with the governer system but that is for another day.

This is what I have been able to find on an e-smay ad as a manufacture part number on the current tach installed.
501D1- GP1

 

[swiss]

VT did you ever get down and look at your Tach? For an update, we are pulling 40 mph at 2k per the tach which is about right. At 1900 rpm the vibration kicks in and gets worse. I pulled the inspection cover on the bell housing and found a .25" ball that we are thinking is from the pilot bearing. It looks like time to pull the tranny which sucks and start removing variables.

 

[Danl]

Danl M915A1

I don't Know Alot about this truck , But the Pilot Bearing as you called it I think its a Pilot Bushing. Your Throw out is a bearing, you said that you got Vibs when you held the cluch in,. The throw out bearing, is conected to the cluch linkage the pilot shaft runs throught it. this is the bearing that pulls the clutch off the Pressure plate when you step on the clutch. You only have to pull the Back half of the Tranny to fix this, no need to pull the Bell housing . you will need a tranny Jack or you will have a hard time pushing the Pilot shaft through the throw out bearing, With out the throw out falling off the clutch fork

 

[vtdeucedriver]

I was down there and I totally forgot to look!!! I need to head there tomorrow if I have time after work. Pm me your number and I will call you with the info. There are also two M-62's in the classifieds with pics of the panels, maybe you can make out those part numbers.

 

[swiss]

I don't Know Alot about this truck , But the Pilot Bearing as you called it I think its a Pilot Bushing. Your Throw out is a bearing, you said that you got Vibs when you held the cluch in,.

Danl thanks for jumping in on this. It actually is a Pilot Bearing that is mounted in the flywheel. I have attached a picture from the TM for reference. I would agree that typically these are bushings but given the weight of the pressure plate and such I guess they used a bearing.

I am going to start a new tread on this so please do provide more input on the new thread as this one has us perplexed.

VT, if you get a chance please check your numbers but no panic, once I had the GPS verify the speed it seems that the tach is now not part of the equation.