M916-M920 Tech & Tips

[R Racing]

I think he means the 1 in the tachograph. Perhaps he will chime in and give us a better idea.

 

[Floridianson]

When shifting into 16th gear, at highway cruising speeds, a red light flickered in the top of the dash gauge, the one for speed and engine speed. What does the light indicate? I was about 2000 RPM.

It means your bumping the governor. Your motor should turn 2100 mine is turned up to 2400rpm

FTRTD

 

[Castle Bravo]

The light in my tachograph turns on at 65 mph, I've always thought it was an "overspeed" light.

 

[Floridianson]

The light in my tachograph turns on at 65 mph, I've always thought it was an "overspeed" light.

If I get a chance to fire up the 920 Monday and I will take it to the governor in first gear and see if I am correct.

 

[R Racing]

The 1 on the tachograph only comes on after 50 ish. it doesn't seem to be linked to the tach .

 

[goodguyzy]

My overspeed light comes on at 53 mph.

 

[gpp111]

The small red light on the tachometer/speedometer gauge (near the top) came on around 50 mph and 1900 RPM, was flickering, clearly I wasnt pushing her too hard, want to make sure the light isnt a problem because she sure settled down in 16th at this speed and it felt like she could do much more. I took her back to 15th until I could find out what the light meant.

 

[goodguyzy]

I run mine max 2200 rpm, im sure you could run it harder but I don't want a busted engine.

 

[R Racing]

Mine runs in the red most of the time. Nothing to worry about. What will scare the bee geebeze out of you is go down a small hill with the pedal to the medal in 16th gear. and see what happens when you go up the hill on the other side lol It got my attension til I read the manuals deeper

 

[Bighurt]

Mine runs in the red most of the time. Nothing to worry about. What will scare the bee geebeze out of you is go down a small hill with the pedal to the medal in 16th gear. and see what happens when you go up the hill on the other side lol It got my attension til I read the manuals deeper

Curious minds want to know, I couldn't find anything in the -10 that jumped out at me. In the engine retarder section it eludes to after 2300 rpm the tranny disengages, that maybe what you are referring to. Would scare the crap out of me if I didn't have any gears starting up hill.

 

[av8or]

Has anyone had this transmission disengagement issue at 2300 rpms w/wo the retarder? That would be a surprise.

 

[R Racing]

Curious minds want to know, I couldn't find anything in the -10 that jumped out at me. In the engine retarder section it eludes to after 2300 rpm the tranny disengages, that maybe what you are referring to. Would scare the crap out of me if I didn't have any gears starting up hill.

That was exactly what I was talking about !! scares the beegeebees out of you ( thought I had broken something) . once your speed drops to like 50 it re engages by itself. But until it does your free wheeling ! That's why increasing tire size is better to increase your top speed then increasing your rpm.

 

[R Racing]

Has anyone had this transmission disengagement issue at 2300 rpms w/wo the retarder? That would be a surprise.

Its my understanding that it will disengage at 2300 rpm even with the retarder on as it is there to keep you from blowing up your engine.

 

[Floridianson]

Yep I was wrong. There is no excuse for not reading the TM. I have had the 920 for years and never had it up to 2000rpm in 16th. I am on 53,s and took her for a ride and dang she was rolling faster than I like to drive these MV's. I like 45 to 50. OK as per the manual the red light is comming on at 2000 rpm letting you know there is a overspeed and the transmission is going to disconnect from the motor and when that happens the motor/jakebrake is not going to help you slow down.
I am guilty of FTRTD. Failure To Read The Directions so this morning going over the 7155 manual I read this. If when in a quick stop you can skip the single shift down shifting but lifting up on the shift handle. I have been useing this the outher way when I up shift. When I do play with her she is empty and I do use the lifting up on the leaver to skip more than one or two gears. I can see where if there was a load on her then skipping two many gears would be bad but when I skip maybe three or four at a time she seems to like it and there is no funny grinding or acting funny. Maybe I am wrong and the manual is right but it feels like it likes me skipping more when unloaded on the up shift.

 

[Artisan]

I would love a picture of this light you speak of... or is it
really IN the TACHOGRAPH?


Also, I am quite sure the directions say to NEVER lift up and shift
unless the truck is STOPPED. Here I found this in the book;

"Use of the inhibitor override when the truck is in motion
is prohibited. The shift inhibitor override should only be
used when the vehicle is at a complete stop.

"

Hard to say who is right, the book or you but I can see your point.
I might try it unloaded...

But I can't find this overspeed light! PUNT!

 

[Floridianson]

I don't know my reading is comming from the Cat service manual. Yes it is in and on top of the Tachograph

 

[Artisan]

TM 9-2320-273-10
PDF PG 118

"
Use of the inhibitor override when the truck is in motion
is prohibited. The shift inhibitor override should only be
used when the vehicle is at a complete stop.

"

 

[Floridianson]

TM 9-2320-273-10
PDF PG 118

"
Use of the inhibitor override when the truck is in motion
is prohibited. The shift inhibitor override should only be
used when the vehicle is at a complete stop.

"

Yep and Yep. The truth, I don't think I will stop up shifting useing the inhibitor when unloaded.
The TM's also tell us to start the Deuce in first gear and anyone who know how too drive will tell you second low unloaded good ground is not a problem to start in. Heck I start my 816 at 36,000 lbs in second low and no problems.
I would think they worrie more about a nondriver down shifting the 7155 useing the inhibitor skipping two many gears for what the road speed is and that's when the bad bad would happen. If it feels good I do it.

 

[R Racing]

I have used it a few time while going down the road with no issues. I mostly use it at stops to get back to 6th or 4th ( the gears I normally start out in. )There a tuff trans if your manifold is behaving . I have seen if the shift piston O rings go bad could cause a 12th or 13th gear to break. But its not common . There fun as heck to shift, And once you get use to it you make that truck move out fast !!

 

[Floridianson]

Now i'm not saying not too read the TM's heck if I would have read the Cat manual I would have known what the light was. I have not played with the 920 much after I got it and ordered the Cat manuel threw it in the shop and thats about as far as I rember. This was a good lessen for me.
Now back to the shifting. I see the motor and transmission as being the strong point but the transfer case being the weak point. If you were to down shift two many gears and to high of a ground speed you would pop the transfer case. I believe if you were under heavy load upshifting and skiped to many once again there is going to be a large load on the transfer case. Sometimes if we don't go past what they say we can do we would never know if we could. I know most of you guys have a lot invested in these machines and love them so do what you feel is right. For me I like to push and if I pop something buy up shifting different than what the TM says I guess I will pay for it and fix it. To add the service manuel also said this transmission was put in track machines too and with a lot of power there is a weak point and you just have to hope you are not the one too find it if it is not your machine.