Auto Tranny - can't hold torgue in overdrive gear

[hey_obie]

I have an 89 TSI with an automatic transmission. The tranny works fine, but when I am in the overdrive gear (going 50-60) and I push the gas down pretty good to spool it up, the clutch can't hold the torque.

 

So my ignorance on automatics is showing here. I have replaced a clutch on my manual 88. But my understanding of automatics is zero.

 

Is my problem the clutch or do the bands need to be adjusted?

 

Is the clutch kit the same for an automatic and a manual?

 

Thanks,

 

Obie

[Caspian]

The transmission needs to be rebuilt. The SC Thunderbirds had this problem as well. The bands are probably slipping in it. You may want to check the fluid and have it flushed and replaced. It could buy you a few months or years.

[Shelby]

you need to try and stay off boost in OD,, realy no reason to boost OD as 3'd will do you up well over a 100 mph

take the time to read up on how to adjust the bands on your auto,,it's not real hard , and you should do all the bands at the same time ..

and NEVER continue to make the trans slip when it does,,let off the throddle as soon as you feel any slipage,, all you'l do is spend a lot of money real fast by makeing it slip excessively

 

the bans are a good quality but they have limet'd area to alow for wear with slipage,, a good adjustment may alow you to go for a good long time as long as you do not slip it a lot

 

a sliping band causes a lot of heat and wears the friction material off the band surface very fast

just as sliping the 5 spd clutch on purpous does

[hey_obie]

I don't boost too often in OD. If just sort of happens when I am going up long hills. Once it starts to spin, I back off or kick it out of OD.

 

I will try to adjust the bands and change the fluid (I changed the filter and fluid about six months ago). I have a lift so I can easily reach them. I assume the adjustment is from the bottom.

 

Is the adjustment procedure in the manual?

[John86TSi]

Yes, the adjustment procedure is in the auto tranny section of the manual. The 1 to 2 shift band adjuster is inside the pan, and the OD band adjuster is under the triangular shaped small cover on the bottom of the tranny near the OD section (can be adjusted without removing the pan). The adjustment is the same for both... loosen the locknut, tighten up the band adjuster till your torque wrench says 10 ft. lbs., back off the adjuster exactly two turns and lock the locknut back down. That is all there is to it.

 

John86TSi

[hey_obie]

John86TSI,

 

Man, you make it sound so easy. Thanks. I am printing your detailed instructions and will take care of it.

 

This is the best website in the world.

 

One thing I don't understand about automatics. I have never pulled one from a car and looked at it. But my question is about the clutch. Is the clutch/pressure plate the same as in a manual or is the clutch contained inside the automatic?

 

Thanks

 

Obie

[JustPaus_88TSi]

No clutch or flywheel..

 

Auto's use torque convertors and flex-plates.. There's multiple clutches in an auto, but not like a big one in a manual..

[Shelby]

spend a little time looking thru the auto trans section of the manual ,, you'l be glad you did

 

to answer that last question clutch packs can be any where from 3 to 6 or more disks stack'd in a drum,, basicly they work just like a standard clutch, but they are press'd togather by hydrolic pressure

not a spring ..you'l have a reaction plate, a fiber disk , a metal plate , another fiber disk, and so on , when the hyd pressure is apply'd they all become a solid part and transfers the power thru the gears to the out put shaft,,much the same as a reg 5 spd , when you press the clutch petal and release it the disk and the fly wheel become one part spining togather

slipage acures when the pressure holding the clutch disks togather is over come by the tourqe being transmit'd thru the gear system ,,just like what happens with a weak pressure plate

but the 5 spd disk has a lot more material on it then the auto disk, so they can not handle too much slipage , but at the same time the total area of all the auto trans disks is many times that of a standard clutch disk and they can hold a lot of tourqe if every thing is in good shape and with in adjustment

 

our stock auto is set up to handle a good deal of tourqe and load, but as we mod the cars we have a lot more tourqe and hp going thru the clutches and bands,, factory spec and adjustments for internal pressures is not set up for optimal shifting and performance, most people would not like to drive a new car that every time it shifts the rear tires bark rubber even durring a moderate excelleration , but if your realy wanting that auto to hold up under all this add'd hp , you need to do a little modification to the valve body and system pressures to asure the firmest and tightest shifts you can live with,,to minize the amount of slipage durring and after shifts under boost ,,slipage is your worst enimy cause that mean heat and wearing of the friction material on the disks and bands

 

now every one with an auto car is not likely to be happy with a neck snaping shift all the time,, so you need to very the shifts acording to your level of mods and how you are going to use the car

the best over all swap you can do to lower the stress level of the uato trans is to go to 3.90 rear gears, this will lower the amount of shift stress a great deal and improve the normal driveability of the auto car all arround,,sence it's gear'd too tall to start with

[mikec]

To add to what Shelby and JustPaus_88TSi posted:

on a manual tranny, the clutch stuff isolates the engine from the tranny when you press the pedal, this way you can move the synchros (they "grab" the gears to pick one gear) without grinding gears.

 

On an auto tranny, the engine connects to the tranny via the torque converter. This thing is NOT a clutch... it's more like a pair of propellers. Imagine one propeller connected to the engine: the engine spins it. The input of the tranny is connected to the other propeller... the "blast" from the 1st prop spins the 2nd prop. That's how power gets through. This is way over-simplified but you get the idea. There is NO MECHANICAL CONNECTION between the engine and the tranny on automatic equipped cars. The torque converter is a "fluid coupling" device - the propellers spin in auto tranny oil rather than air. Because there is no rigid mechanical connection it's possible to have different RPMs going in to the torque converter than what's coming out of it. The clutch packs inside the auto tranny pick a set of gears to determine what gear the tranny will use; they do roughly the same job as the shift lever and synchros on a manual tranny.

 

Manual tranny: the one and only clutch lets you "disconnect" so you can shift. Clutch is mounted to flywheel on the rear of the engine.

auto tranny: the various clutch packs DO the shifting. They're deep inside the tranny too. The torque converter, mounted where the flywheel would normally be, provides the RPM translation between the engine and tranny instead.

 

Instead of two props facing each other, torque converters really have a set of vanes turning near another set - almost like two fans/propellers facing each other. And they're called impellors instead of propellers.

 

Because the torque coverter is always turning with the engine, auto trannies want to creep when you're sitting at a light. Engine is still turning... but the output of the torque converter (input to tranny) is NOT turning... but torque is still going through the tranny, trying to push the car which is why you have to sit on the brakes.

 

Under normal circumstances, the torque converter impellers turn at different RPMs. For steady highway cruise they're pretty much the same. As long as you're driving at higher speeds, and steady throttle, - AND NOT SHIFTING - the auto tranny doesn't need the torque converter so it can "lockup" which is a mechanical device that basically clamps the impellers together. That eliminates a little bit of power loss due to inefficiencies and not perfect coupling of the torque converter impellers.

 

mike c.

[Shelby]

to continue with this,,the OD is not a one part gear set,, it consists of the OD gearing and the tourqe convertor locking up , so when your trany shifts in to OD it is actualy doing two things, one the OD band applys and the convertor lock up is apply'd , acording to the FSM the lock up raises the rpms by aprox 200-300 , that plus the gear ratio diff gives you the 800 to 1000 rpms diff when going from 3'd to OD

the exact rpm is a little diff from one unit to the next

[mthomlinson]

It sounds like 3.90 gears is the way to go with the auto. What would be the most cost effective way to change out the 3.54

[Shelby]

It sounds like 3.90 gears is the way to go with the auto. What would be the most cost effective way to change out the 3.54

 

do them your self :roll:

[mthomlinson]

Shelby, is one of your cars an auto?

[Shelby]

just my toy,,the truck, :wink: ,all the cars have been 5 spds

[hey_obie]

Where would you gets the gears for a 3.90 rear?

 

Thanks for education on the auto versus manual.

 

Obie

[Shelby]

some of the guys are lucky and their local you pull it's are not crooks like the rest of the country,,and they can get good prices on stuff, just have one of thm price you a set ,,contact yellowhell

 

as for learning a bit about the auto,, it takes longer to learn how to race an auto then it does a 5psd , but an experiance'd auto street racer can hand your your a** in a hurry if your not real carefull

[BaltTSI]

Do the manual tranny guys argue the thought that an auto will be faster? I can't remember too many debates on here about that, for one, an auto doesn't drop boost between gear changes, but the ratio isn't as good as a manual right? any other pros and cons between the two?