Stress on Engine When Engine Grade Braking
- Thread starter MrkofXcellence
- Start date
You don’t need to rev match a traditional automatic that is coupled to a torque converter. Not sure where you got the idea from that it helps with anything. It doesn’t and may actually put more wear on the plates as you have no control how they engage/disengage.
It’s typical bitog drivel. We have countless pages of people discussing this kind of silliness, or how to torque the oil drain plug, or how quickly one should put the car in D after a cold start. Pages and pages of people theorizing this silly stuff.
unless hauling some load or pulling a weighted trailer the vehicle will take care of itself. modern vehicles have overbuilt cooling and oiling systems i can be in bumper to bumper traffic 110 heat index my oil temp sits around 190-194 putting a load on the vehicle what I may see 210-212. My biggest concern would be overheating the brakes as long as one is diligent on vehicle maintenance when it comes to oil changes GDI and turbo engines could benefit from a little spirited drives.
Are we talking about downshifting an Automatic transmission into 3 or 2 from D ?
Wouldn’t that put entirely too much stress on the trans?
Wouldn’t that put entirely too much stress on the trans?
Maybe it's vehicle dependent, but on the one mountain pass I occasionally drive going up the mountain the oil temps rise as expected, but engine braking going down it goes down a good bit. This is on the WRX, 6MT.
We had the CVT in an Outback and it was really weird "downshifting" it going down the mountain. It more or less just made a bunch of noise and didn't engine brake much.
We had the CVT in an Outback and it was really weird "downshifting" it going down the mountain. It more or less just made a bunch of noise and didn't engine brake much.
"you don't need to", but you'll wait at least a second or two for it to wait for the engine and axle speed differences to be closer before it tries to slip into gear.... so how can that not put more wear on the clutch packs when just blipping the throttle while it's doing that minimizes the speed differences and gets it into the lower gear faster? this wear is why transmission builders and trainers always discourage engine braking in an automatic and just use the brakes as much as possible
In my experience automatics just unlock the torque converter and jam it in the gear you asked for and let the torque converter slip instead of the clutches.
The only exception is my old Mitsubishi where if you're offroad and go 2nd to 1st coasting at low speed it takes a second to shift but I think that's because there's not much fluid pressure at 600rpm.
How do you know your throttle blip is not revving up the engine while the clutch packs are engaging and as a result puts more wear on them vs. lower RPM? Throttle blips help with gear matching not clutch wear. And since the torque converter is also slipping during gear change, you simply have no idea what's really going on, unlike in a manual transmission.
You have simply concocted this idea that it somehow helps with clutch pack wear out of thin air.
Yup, that's how it works even to this day. The majority of slippage is taken by the torque converter and the rest by the clutch packs to make the upshifts and downshifts feel smooth. All of that happens simultaneously and there is no way to "squeeze in" a manual throttle blip in there. And since automatic throttle blips have been available for over a decade now, but are still missing from the torque converter automatics, that tells me they are not needed to be there.
ok, explain how upshifts happens then, because they don't just slam themselves together and "let the torque converter slip"... that's how you bark you tires between gears....
and how do you know it's not free wheeling and the clutch packs are engaged? you can't feel what's going on under the hood?
I've done this for tens of thousands of miles in a old beater toyota I bought for $500... it downshifts SLOW and it's electronically controlled, not hydraulically governed... I drained the fluid every 30k, long after I bought it well neglected and abused with god knows when the last time the fluid was changed before I got it... the fluid was still cherry red when I drained it every 30k, at 250k miles... not full of clutch material, not dark
The clutches also slip. Your throttle blips have absolutely no effect, nor can they be time correctly to have a positive effect.
What can I say? Something is wrong with that transmission and your practice perhaps increases the oil pressure enough so that the clutches engage faster. But that doesn't mean it's good practice on a properly working transmission.
There's nothing wrong with that transmission or any other old Toyota transmission... they all do that... slow downshifts from high speed... you're going to be coasting downhill with no engine braking whatsoever because it's out of gear for more than a second while you're waiting for the transmission to "catch up"
Unlock t/c slam next gear lock t/c
Most cars don't make enough torque to bark the tires between shifts (unless it's a diesel
)Cruising at low throttle or accelerating gently the torque converter often stays locked and it just uses the clutches to shift
Most old cars with cable actuated throttles don't even cut power when shifting. New cars might if they have a weak transmission design and GM doesn't want to make it stronger or they make 300+ hp
old cars always have the torque converter clutch disengaged during acceleration/shifts.. only once you're in stead speed above a certain speed (say 35mph) does it actually lock up, then light acceleration from there might keep it locked until it decides either by ECU or kick down cable that it needs to downshift and unlock the torque converter... and usually the torque converter lockup happens only in overdrive or in the 1:1 gearUnlock t/c slam next gear lock t/c
Most cars don't make enough torque to bark the tires between shifts (unless it's a diesel
Cruising at low throttle or accelerating gently the torque converter often stays locked and it just uses the clutches to shift
Most old cars with cable actuated throttles don't even cut power when shifting. New cars might if they have a weak transmission design and GM doesn't want to make it stronger or they make 300+ hp
only modern cars does more torque converter lockups than old ones
and in those old cars, they "don't cut power" during upshifts but they pull back ignition timing to reduce power to soften the shift
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Japanese cars from the 90s onward do that. Maybe domestics don't
I have an 8 degree downhill slope on the way home. I shift from D to M near the edge of the hill, proceed down, then give a tap on the brake to disengage the cruise control and signal to anyone behind I’m going to slow down. With my foot lightly on the brake I electronically shift from 6th to 5th and can feel the revs rise as the transmission gears down. I then coast down the hill without touching the brake and shift back to 6th at the bottom.