Downshift floating

It has to do with the synchronization of the gear wheels and what y macallits in the thing a ma jigs.

 

When I learnt to drive big rig trucks I was told to learn how to shift going up and then down.. You're doing it right like I learned lol. When down shifting think of the rpm you were at coming OUT of that gear into the next one. For instance shifting from 7 high to 8 low you'd need to be let's say around 1500. So when down shifting from 8th low to 7th high you'd let the motor lug down to let's say 1100-1200 and then give it a shot of fuel to around 1550 and it should slide right in. Every truck and tranny are different. Once you figure one out you'll have them all figured out.

 

Gearing...

 

I'm not 100% clear on the question you are posing, but since we were talking about rpm "steps" between gears, I'll assume that's what you're asking. And that, as you know, is all about the trans gear ratios.

If you're asking about shift points, I guess it depends on how big of a hurry you're in and whether of not you are paying for the fuel. You can floor it until the power drops off and then shift. Or you can wind the engine up only as far as it needs to be revved so that the engine is just above peak torque after the shift. With my little M11, 13OD, and 4.33 rear I can shift at ~1450 and she will still recover just above 1200 (peak torque) and pull herself back up.

How did I do?

 

So on the upshift it's 250 rpm. What is the rpm range on a downshift? 400-500 rpm?

 

No silly. It's theoretically the same step between the ratios doesn't matter if you're going up or down. Why do I feel like this is a motive power exam and why am I the only one in the class?

 

Not even "theoretically": it's the same upp or down,as long as you're not skipping gears.

 

I got good at it in traffic jams. Its no point in having your Jake brake on unless you're going down a steep down grade, but I would just to help me get faster/better at shifting. I always down shift from 10-8 8-6 6-5. Bump it up 600 rpm's for two and 300 for one.

 

New trucks don't like it and older trucks that have always been double clutched don't like it either because it still acts like a new one. I had a truck that was about 6 months old and it did the same. After around 30K miles of forcing floating it finally opened up to it and became easier. I don't understand the mechanical side to why its that way. My trainer back from when I was in a CDL mill was given a new truck 2 weeks after I got on his truck (old ragged out POS) for a brand new one. Same problem. Gears were really tight, much closer together and didn't like floating but when I finished out my 60K miles before getting my own truck it floated like a knife through butter. Personally from those experiences I don't care for a brand new truck. I would rather have something with at least 60-100K miles on it. Call me crazy but I don't like how tight a new truck feels. Kinda gives the feeling of being restricted as far as the tranny goes.

 

Theoretically because it depends on how fast you can float down. Your ground speed may change more when down shifting than upshifting.....as I am sure you know from driving that bus and reading about those F1 cars.