Tach not working.

[Flyboy]

Hi,

Started my 4104 up yesterday after a prolonged sit in storage.  Tachometer not functioning. 

Does anyone have MPH values that correspond to each gear range for a 4 spd spicer trans/6N71 congfiguration I.E. bottom and top end RPM vs MPH?  I will then be able to use my GPS to estimate for shifting.

Also, any suggestions on where to start troubleshooting the tach?

Thanks.

FB.

[bevans6]

It's actually easier than that.  Just let it rev till it stops on the governor, then shift.  No need to look at anything for most gear change situations.  What differential do you have and what size tires?

Brian

[Cary and Don]

This might not be the same on your bus. Our tach runs off the "R" terminal on the generator.  If the tach isn't working,  the regulator board isn't working.

Don and Cary
GMC4107
Neoplan AN340

[RJ]

FB -

To answer your question:

1st = 15 mph
2nd = 30 mph
3rd = 45 mph

Give or take a couple mph, these are the normally governed top speed in each lower gear of your 4104's powertrain.  When pulling a grade, start your downshift approximately 5 mph over the top of the next lower gear.  Do it right, and it will be nice and smooth.  Otherwise, keep practicing!

As Brian said, run it to the governor in each lower gear and hold it there to get your GPS speed indication.  That's the way they're designed to be driven under acceleration anyway, and it will not hurt the engine at all.

FWIW & HTH. . .

[Flyboy]

Hi Brian,

11R 22.5 is the tire size, don't know about the diff.  I recently sold the bus and the guys are coming to pick it up.  If I can't get the tach working I'd like somwhere for them to start.  Both are novices so my pro bus driving friend is going to get them up to speed.  It's just bad timing when you're first getting going as a driver, it would be great help if it was working. 

I never look at the tach myself when I'm shifting except for watching trend on upgrades and descents for the jake but I've been driving this machine for quite a while and it's no issue.

Thanks RJ...gives me somwhere to start.

FB.

[bevans6]

RJ's idea is what you should probably do - take it out, run it up and note the speeds, then put them on the speedo face with erasable marker or tape.

Brian