Adjusting auto tranny fluid pressure - Fuelly Forums

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Old 04-01-2006, 08:41 AM   #1
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Adjusting auto tranny fluid pressure

My wife has a 2003 Honda Accord with a 5-speed auto. The fuel economy on it is not optimal on the thing, and I think part of the problem is the lag in shifting. I know that in some VWs and in the Toyota Camry, there's a way to adjust the transmission fluid pressure to make the transmission shift sooner. This results in better fuel economy since the engine won't lag in a lower gear.

I was wondering if anyone knows if it can be done for the Accord.

Thanks,
Jeff
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Old 04-01-2006, 09:34 AM   #2
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I would start by checking

I would start by checking the transmission fluid levels and making sure everything is fine there. If there is too much or too little it will affect your shifting.
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Old 04-01-2006, 12:03 PM   #3
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Yeah, the fluids are all

Yeah, the fluids are all good. This is just how the transmission has behaved since day one. It's slow to switch from 1-2 and 2-3 but is okay with 3-4 and 4-5. It could probably be better, though.

Jeff
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Old 04-01-2006, 12:05 PM   #4
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there should be a huge

there should be a huge resistor right next to the tranny that controls your line pressure. Some people disconnect it when racing and they get fast hard shifts.

By using a different resistor or modding the current one you can change the line pressure and affect your shifting. By disconnect it for regular driving will kill your tranny over time. It can't take full line pressure for a long time.

The 1-2 shift just blows on the new accord. It feels as if you lose all power then all of a sudden you're in second.
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Old 07-30-2007, 09:06 AM   #5
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Wish I could give you more of an expert response. All I can say is that this is a common gripe with auto trannies. They're usually designed for "mushy" shifts so that average drivers won't complain that shifts are too hard. Imagine you're driving a stick-shift, and you're taking a looong time to bring the clutch all in after you shift, letting it slip so you don't feel a "bang" into the next gear. That's what it's doing.

The good news is that it's an old problem that most likely has a fairly inexpensive aftermarket solution. You need a shift kit. These will change/modify the valve body in the tranny, usually by replacing some parts. These are widely available for older domestic trannies, I'll bet you can find one for the Honda.
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Old 07-30-2007, 02:44 PM   #6
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If the vehicle has a kickdown cable, it can be adjusted to change the shifting characteristics somewhat.

Maybe try tightening it a little and see if you like the effect better.

I did this on a Toyota and it made it more eager to change down and the changes were harder.
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Old 07-31-2007, 06:35 AM   #7
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If the vehicle has a kickdown cable, it can be adjusted to change the shifting characteristics somewhat.

Maybe try tightening it a little and see if you like the effect better.

I did this on a Toyota and it made it more eager to change down and the changes were harder.
This is a good idea as it's easy to adjust and easy to change back if you don't like it. It's basically a throttle reference so if it thinks you're deeper in the throttle it will shift differently.

The Accord may be fully electronic though...
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Old 09-25-2007, 09:24 AM   #8
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Question Hard Shifts vs. Throttle Cable

On the '98 Integra:

Earlier this year, I discovered that my throttle linkage pulled loose and only provided enough fluid pressure for a partial TC lockup -- after increasing the amount of engagement significantly, FE went up and I get TC at exactly 35 mph MOST of the time... More on that in a moment.

The side effect is a hard shift. To me, this transmission always shifted hard, but more so now than before. I "shift" the car myself like most auto drivers, lift the throttle and it upshifts.

When I do this, it usually results in a hard shift and loud "clink" sound and something you can definitely feel. On auto 3-2 downshifts it does this too with an annoying lurch and clunk.

So the question: is this worse for the transmission than loosening the cable tension/travel?

With the TCU and hill-logic BS, the kickdown cable only provides performance-oriented kickdowns and fluid pressure regulation -- the chip takes care of the rest. In other words, it doesn't downshift too soon like other vehicles with tightened cables. It does just the opposite: TC locks up sooner.

What I've noticed this summer:

Unfortunately, the TCU doesn't like EOC-ing. It generally confuses it, resulting in delayed TC lockup under normal circumstances. Basis for this argument: Hill-logic calculates speed change, load, TPS, coolant temp, etc. to decide on TC engagement and/or gear hold. When EOC-ing with the key-on, the calcs become skewed, and it refuses to engage the TC until the equation is satisfied (still using "bad" data from the coast). Bottom line, throttle cable position is moot in this situation.

The goal with this car is to have everything last as long as possible while still achieving good FE. That includes the tranny (even though I'd love to swap a manual in there, but money is what it is)...

RH77
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Old 09-25-2007, 09:59 AM   #9
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From my personal experience with GM auto trans particularly the 4 speeds found in the 88-95 Grand Prixs (specifically the Turbo Grand Prixs of 89-90). We would always install an adjustable vacuum modulator to firm up the shifts on a stock trans. In an automatic trans like GMs, if the shifts are soo smooth that you can't feel them...that is bad. It means that the friction plates and steels are sliding on each other way more than they need to. This creates a lot of extra heat and wear on the trans parts. In fact, 4th gear would usually melt/fuse together causing the trans to stay locked in fourth gear so when you came to a stop, that was the end of the trans.

The faster/harder (to a point) the discs lock together when shifting, the better for longevity of the trans. We would adjust the modulator so that shifts were on the edge of what most people would consider firm. you could feel the car engage into the next gear solidly.
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Old 07-22-2008, 08:49 PM   #10
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My Hyundai shifts way to smooth. If anyone knows about Hyundai autos please share. Otherwise, I'll look for a resistor near the trans. or see if a Hyundai mechanic has any tricks to get this thing to shift firmer. When I find out, I'll post the info here.
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