thud when starting up the engine and switching to Drive

The situation: at a red light, especially a left-turn one, I shut off the engine, placing the trans in neutral. Suddenly the light turns green. I turn on the engine. I'm near the front, and in a bit of a hurry. I slip the gear into Drive, then press on the accelerator. I feel a noticeable "thud" as the car shifts into drive.

What is this thud, exactly?

Is it bad for the longevity of the trans?

Thanks,

Michael

Reply to
mrdarrett
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When you're not in a hurry to accelerate. For example, start the engine (the engine speed stabilizes to normal idle), and then shift. Do you still feel the thud?

Typical questions: How's the condition of the ATF (pink/red, grey, brown, black)? Strainer (not blocked I'm sure but with/without tiny particles visible)? Last service (month, years, never)?

If you take it easy and there isn't a thud, then there is a bit of delay in going into gear. My guess is slow ATF pressure rise. For example, the older v6 tranny (the budget 540 series) was notorious for sluggish pressure rise (therefore accelerated clutch friction wear, and the downward spiral continues), and IIRC a steel valve sleeve was made to delay the wear in later years.

Reply to
johngdole

Now suppose you just step on the gas from a stop. Say at a left turn, do you feel the thud?

Another possibility: inner CV joint. I'll try to find some articles on this.

Reply to
johngdole

Oh the trans is fine otherwise. I drained and filled numerous times chasing another problem (eventually solved it), even changed the strainer once.

Slow ATF pressure rise sounds reasonable. Wears out the clutch, eh?

Thanks,

Michael

Reply to
mrdarrett

It's probably the delayed or slow shifting that John mentions. Equally important, though, is that you shouldn't be doing that - shutting the engine off at red lights. I know hybrids do it, but they are designed for it, and your car isn't. If you are saving any gas at all, it's being more than made up for by accelerated wear in the starter and transmission. If you're doing it because of the notorious Camry 'shaking at idle in Drive' then just shift to Neutral, leave the engine running, and when you see the light go yellow on the other side, shift back to Drive. Never press the gas pedal before you feel the transmission engage. We have a '95 wagon that was neglected before we got it, and the transmission is very slow to shift into Drive or Reverse; it's taken a conscious effort to remember to wait for it to engage before stepping on the gas.

Reply to
Leftie

I was doing it to save gas. Heard that the fuel injection system doesn't use much gas to restart, compared with carbureted engines. I'll keep in mind the stress on the starter though, thanks.

It's a '96 camry, 164,000 miles, thought I'd try to hypermile a bit. Saving the car for my brother-in-law, else I'd sell it already.

I had the stalling problem at red lights, and fixed it by replacing the coolant temperature sensor. (At first I thought it was a stuck torque lock solenoid, so I changed the coolant every oil change... turns out that wasn't it.)

Thanks,

Michael

Reply to
mrdarrett

Whoops, changed TRANS fluid every oil change (not coolant... that would be silly...)

Thanks,

M
Reply to
mrdarrett

I take it that in typical starts this thud doesn't happen? I think with Aisin transmissions it can take about 0.5-1.2 seconds to shift into gear. The new transmissions of choice, Borg Warner Direct Shift Gearbox designs (DSG) would need only about 8 milliseconds.

So try stepping on the gas 0.5-1.2 seconds AFTER shifting. If that solves the problem all is fine.

Otherwise also check inner CV joint and possible differential (spider gear) problem. Here is an article on CV joint (inner and outer) noise diagnosis:

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Reply to
johngdole

Reply to
johngdole

Reply to
johngdole

I practice what I like to call "Super Miling." I don't do anything extreme, just accelerate very gently unless traffic warrants otherwise, coast a lot (the Camry has a great little clutch in the automatic that disengages enough to get most of the benefits of coasting when you take your foot off the gas), keep the tires at about 38psi, and try to time lights so I don't have to come to a complete stop at them before they change green. I get 27 (Winter) to 34 (Summer, mostly highway) on average. The wagon averages about 1mpg less than the sedan. Amazingly efficient car for its size. I don't think shutting it off at anything other than 5 minute red lights is worth it.

Reply to
Leftie

Simple fix, dont stop the motor for 2 minute lights. How about starter wear. On startup and shifiting mine thumps, yours was not designed for this as the trans looses pressure id guess. Do you really save gas, a tuneup and mobil 1, 0-30 or 5 -30, will save gas you will see.

Reply to
ransley

red

Reply to
mrdarrett

Wow, tires at 38 psi? I think I'll try that.

Typical left turn red lights here are ~2 minutes. We used to have a terrible one that was 5 min tops if each of the light rail trains happened to coincide with the left turns... nasty.

Michael

Reply to
mrdarrett

Setting the tires at 38psi cold will net you more fuel savings than stopping the engine at even 5 minute redlights. It's usually good for

1-3mpg over tires inflated to 32. I suggest to people that they go 10% below the maximum pressure printed on the sidewall, and to lower that a bit if the ride gets too rough or if oversteer appears. 38 seems to give the best combination of good mileage and decent ride.
Reply to
Leftie

How often was the differential fluid changed? IIRC the 140E has a separate sump for the differential.

Yeah, with that frequent of ATF changes your transmission should be in good shape.

Reply to
johngdole

I'll do 35 psi as a first test. We'll see how it goes...

Thanks,

Michael

Reply to
mrdarrett

Have you checked the motor mounts?

Reply to
NickySantoro

I changed the dog-bone mount several years ago, but this thud only happens when I rush the shifting. No thud in normal driving.

Michael

Reply to
mrdarrett

You are faster than your transmission. ;)

Do plan to give it 0.5-1.2 sec> I changed the dog-bone mount several years ago, but this thud only

Reply to
johngdole

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