Maxitorque 2070 shifting help

[SpreadingLime]

Hello all. This is my first post on the site, so please bear with me. Im sure this topic had been beat to death.

I am the new owner of a 1888 R690, E6300 ( not sure about Eco or Maxidyne) and 2070A. This is the only heavy truck I've ever driven.  It has spent most of its life as a spreader truck in North Arkansas. New Leader 3020 GT bed, 38k camel back.  This ole truck has HARD life.

I am struggling to master shifting.  I have read all I can find on the subject, and talked to everyone who will listen.  Most says that you come out at 1800 and go in at 1200.  That's not working.  I've found that out at 2000 and in at 1600 works much better. That's only for upshifting.  Downshifting is a whole other animal.  It's is very speed sensitive.  Just to go from 7 to 6 it must be around 37 to 34 mph. Any faster, forget it. 6 to 5 works best at about 24.  Forgot to mention that there is no Jake brake.  This results in using the foot brakes ALOT!  

I'm starting to think that the transmission is just worn out. Also do Maxidyne and Ecodynes have different shift points? Any help is appreciated. Thanks in advance.

 

[doubleclutchinweasel]

Welcome aboard.  Shifting a non-synchro box (up or down) is a matter of matching the speed of the engine/input shaft to the rest of the transmission.  "Double-Clutching" takes just a little practice to master.  You have to listen to and feel of the beast to know what it wants.  As far as smooth engagement of the gears, there is no magic RPM.  If it matches, it goes in.  If it doesn't match, it grinds.  That simple.

Now, some engines do have a preferred RPM range to work within.  So, for any combination, there will be a sweet spot where the power delivery is optimized.  But, work out you shifting to get it smooth first.  You may be correct on those downshifts.  That may be the speed you have to be at before you have enough RPM available to make the downshift smoothly.  Or, it may need a different RPM before going into the lower gear.

Each box (and each shift, for that matter) has a specific RPM percentage change.  For instance, your comment about coming out at 1800 and going in at 1200 represents a 33% drop in RPM for that shift.  I don't know the ratios for that box, but that may be a little too much RPM drop.  If, for instance, the drop is really 25%, then it might go in better at 1350 instead.  Your 2000-1600 is a 20% drop, so that might be the percentage you need right there.

And, remember that downshifting is the inverse of the upshift.  That is, if the RPM after an upshift is 3/4 of what it was before the shift, then downshifting that same gear change will give RPM that is 4/3 of what it was before the downshift.  It just takes a little time to get used to it.

And, each transmission will have its own drops.  Obviously, a 5-speed will have far greater drops between gears than an 18-speed.

Pretty soon, you will learn how to unload the drivetrain with careful throttle work, and you will be shifting without even using the clutch..."floating" the gears.  When floating, the correctness or incorrectness of the RPM matching is even more evident!

Just be patient and give yourself time to learn it.

[doubleclutchinweasel]

Actually, it looks like the ratios in that box ARE pretty widely spaced, requiring lots of "drop" while upshifting and lots of "rise" while downshifting.

The MPH on this chart will vary with rear gears and tire sizes.  But, the top and bottom of the RPM changes should be constant.  Looks like shifting around 1750 will drop you to about 1000 on most shifts  (43% RPM drop).  Conversely, you would have to pull down to about 1000 before downshifting, double-clutching up to about 1750 to match the gears and let them slide in (75% RPM rise).

[SpreadingLime]

I have seen that chart before. You're explanation makes it much clearer.  The text at the bottom of the chart refers to a "1750 RPM Engine".  My headliner has a sticker that says "Working range 2100 to 1200 RPM.  This makes me think that I have a Ecodyne engine.  As I understand the Ecodynes worked at a higher RPM range for fuel economy and the Maxidynes worked at the RPM range refered to in the chart, producing the "famous" Mack low RPM pulling power.   I understand and agree with the logic of your response , it may be that the numbers are just different for my particular engine (as you mentioned). Thank you.

[doubleclutchinweasel]

The 1750 engine (I think) were referred to as "limited" or "governed" engines.  But, yes, the PERCENTAGE drop or rise would be the same.  So, if you can go to 2100, then you would drop to about 1200 instead of 1000.  And, you could downshift at 1200, double-clutching up to 2100 to catch the next lower gear.  Sounds a lot like your "1200-2100 operating range", doesn't it?!

[terry]

If you have the 2070 trans with at least a 5.50 rear or deeper you have the maxydyne engine, if everything 

is original.    terry

[Vladislav]

...And mentioned relatively small drop in revs at a shift gives thoughts that the tranny is NOT T2070 but maybe t2090 9-speed or so with much closer gear steps and less drops as a follow. All T200 series trannys look similar in general and sticker in the cab may be obsolete to the current state of the truck.

Worth to mention even if the things are of that way it wouldn't mean big change in the shifting approach. Just as said above, try to feel what the truck wants from you and improve your skills. Than after a bit of time you will learn which revs to go out and in a gear. Crawling under the chassis to look for stamping on the tranny housing may be found as a worth to do thing either. 

Vlad