Metro automatic trans mod.

[engineer93065]

Hi, new member here. I searched the archives, but didn't find mention of this trick, so I thought I would pass it along.
I am driving a 91 metro vert automatic. My commute is 80 miles, approx 1/2 of which is stop & go. The automatic's shift points are all wrong for this, it seldom sees 3rd without coaxing, and downshifts too soon.
I read on Teamswift that these can be run with the shift solenoids disconnected, and shifted manually. So, WTF, I disconnected them for a week to try it out. I discovered that I can keep it in 3rd as long as I am still rolling, start out in 2nd if stopped, and get it into 3rd at about 15-20 mph. This netted me a 4 mpg improvement.
In order to retain the option of full-automatic, I wired in a DPST dash switch to the solenoids that allows me to switch between automatic or manual shifting on demand.
I don't know if this scheme works for other transmissions, but it is the hot ticket if you are stuck (blessed?) with an automatic Metro.
Ray

[Daox]

Sounds like a great mod for an automatic. We don't need no stinkin computer telling US when to shift.

[JohnnyGrey]

For bonus points you could get one of those arcade machine shifters. They have the sweetest throws ever!

[Johnny Mullet]

Damn. I never knew that could be done on a Metro Auto.

[bhazard]

If youre startingi in a higher gear all you're doing is slipping more and heating things up. Youll save a buck or two at fillups but be out hundreds for another trans in the long run.

[engineer93065]

Bhazard,
True the t/c may slip more, especially if I tried to start out in 3rd. 1st gear on these things is ridiculously low however. It gives this little 3 cyl the opportunity to accelerate at a rate that is almost acceptable. In MY daily drive, 2nd gear leisurely starts do not seem to cause noticeable slippage or engine lugging.
In my experience clutch slippage is the killer. This mainly happens during shifts under extreme load. The little Metro weighs almost nothing, and the engine could be best described as wimpy. Not too much loading going on.
If this seems to be an issues, I will put a temp gage on the tranny, & keep an eye on it.
Ray

[MetroMPG]

I'd never heard of this mod before. Very interesting.

[cubano112266]

Very interesting mod. Keep your fuel log updated, I would love to see the benefits to this mod.

[1.5Ldave]

this is an awesome mod! anyone have any idea how to go about doing this on a 91 civic auto?

[dremd]

how about a controller like these? New! Suprastick V4 - standalone tranny computer - SupraMania

[Formula413]

Wow, great mod, I wonder if I could do this on my Escort?

[garys_1k]

I've looked up the wires on the computer that go to my Focus' auto trans solenoids -- I'd love to get it in higher gears sooner and lock the damn thing at 30 mph instead of 40. On my list of things to do, first I want to put a 'scope on the wires to see if they're on/off of PWM'd. If it's on/off I might wire up a simple shifter for it so I get to pick the gear/lock state myself. If it's PWM'd I may have to use something fancier, like a little control computer to handle the shifts.

[metromizer]

If you could figure out how to increase transmission line pressure from the pump, you might decrease clutch slipage (and the heat associated with that). A common trick in motorsports where a slushbox is used. Google 'Mike's transmissions' and 'drag racing powerglide tricks'. I have a GM modification manual for the Ecotec engine that also covers one of the fwd autoboxes... they increased the line pressure on that thing, also.

[garys_1k]

Yes, but at the torque loads I'm using while going for better FE clutch slippage is NOT a problem. More pump pressure = more pump input torque = higher engine load = less FE.

[metromizer]

Originally Posted by garys_1k

More pump pressure = more pump input torque = higher engine load = less FE.

therefore, less pump pressure equal better FE? LOL I'm just having some fun at my own expense.

But seriously, I love the modification, I'm just trying to figure out how to fix a secondary problem (that probably doesn't even exist, but someone above mentioned it).

I am sure there is a happy medium between higher parasitic loses from the front pump and better efficiency through more crisp shifts and less slip. Too harsh a shift and the transmission would undoubtably eat itself up in commute traffic, not to mention spill your coffee. A smooth shifting transmission or a real tall geared one has a lot of slip and therefore must generate heat. Heat is a result of friction, so the coolest running transmission will likely be the most efficient one. A gage might tell the tail, unless the trans cooler is already an over-acheiver. One thing is for certain, the guys who sell new cars want the buyer to experience a good 'feeling' transmission, and low warrenty repairs numbers.

I'm not saying slippage is a problem, but if it were...

On that same note, my '95 Toyota Celica's slushbox was leaking and slipping a little, so I bought this stuff that claims to remedy those ills. I put some between my fingers before feeding it to my Celica, and it was kind of sticky, like oily honey. The claim was "reduces leaks, reduces clutch plate slipage while retaining lubrication and cooling properties of your trans fluid" I don't belive in miracle additives, but it was already leaking and slipping, nothing to loose so I dumped the stuff in. Shifts definately became stiffer (but not harsh), and I noticed FE got a little better, maybe 2mpg. it slowed the leak down. 30k miles later the leak is bigger than ever...

[garys_1k]

Originally Posted by metromizer

therefore, less pump pressure equal better FE? LOL I'm just having some fun at my own expense.

Yes, a lower pump load would cause less engine load. You really only want JUST enough pump output to keep the clutches from slipping. Many modern trans controllers work by inferred engine torque -- they back off at low pedal inputs, or if the ECU commands less torque, to save gas. Also, overpumping when not needed is, itself, another heat maker.

Originally Posted by metromizer

But seriously, I love the modification, I'm just trying to figure out how to fix a secondary problem (that probably doesn't even exist, but someone above mentioned it).

I am sure there is a happy medium between higher parasitic loses from the front pump and better efficiency through more crisp shifts and less slip. Too harsh a shift and the transmission would undoubtably eat itself up in commute traffic, not to mention spill your coffee. A smooth shifting transmission or a real tall geared one has a lot of slip and therefore must generate heat. Heat is a result of friction, so the coolest running transmission will likely be the most efficient one. A gage might tell the tail, unless the trans cooler is already an over-acheiver. One thing is for certain, the guys who sell new cars want the buyer to experience a good 'feeling' transmission, and low warrenty repairs numbers.

Trans. efficiency goes UP with temperature -- to a point. The oil viscosity reduction is good for FE, the metal clearances open up and both fluid flow losses and bearing friction drops with higher temperature, UNTIL the oil is so thin that it looses film strength. Once that happens you get MORE friction and wear takes off.

Originally Posted by metromizer

I'm not saying slippage is a problem, but if it were...

On that same note, my '95 Toyota Celica's slushbox was leaking and slipping a little, so I bought this stuff that claims to remedy those ills. I put some between my fingers before feeding it to my Celica, and it was kind of sticky, like oily honey. The claim was "reduces leaks, reduces clutch plate slipage while retaining lubrication and cooling properties of your trans fluid" I don't belive in miracle additives, but it was already leaking and slipping, nothing to loose so I dumped the stuff in. Shifts definately became stiffer (but not harsh), and I noticed FE got a little better, maybe 2mpg. it slowed the leak down. 30k miles later the leak is bigger than ever...

The big question is what it was like at operating temperature. If it increased the lubricity it might have helped. Worn components may benefit from higher viscosity if it helps prevent metal to metal contact (worn parts often have rough spots, at least on a microscopic scale).

ETA: You mentioned shift quality. Yes, it is a HUGE buy/no-buy issue for buyers. Even Consumer Reports will call out a car with "harsh" or "slow, ill defined" shifting. Knowing what makes a shift feel good, through both the torque and inertia phases, is a refined art. Calibrating all those clutches to get it right can take weeks.