A/T Fluid Change

[steve-gers]

What's the best way to change the transmission fluid in an auto? I've heard it's to remove the dipstick and suck the oil out with a suction pump and replace same amount of old oil removed with new stuff (around 5 litres?) but this doesn't replace the oil in the torque convertor? So if anyone could clear this up and how to change it all by the best method and also the amount of oil required that would be great.

 

[dark_knight]

i'm sure there is a drain plug on that autobox..
last i did something similar, i refilled via the dipstick port..

 

[steve-gers]

I have a guard looking thing under my gearbox so I take it the drain plug would be under there? Also how would I change the oil in the torque convertor? Thanks.

 

[dark_knight]

same box. same oil.

yes sir. you may have to remove the transmission/sump guard to access the drain plug/bolt.

i'm no autobox boy but i would want to believe that just like the LSD 5MTs have the transmission oil lubricate the LSDs -- the t/convertors are also lubricated by the ATF and thus don't need to be 'changed separately' so-to-speak. i stand to be corrected though..

 

[steve-gers]

Spot on so it's just a case of removing the guard then draining via the plug at the bottom then refill via the dipstick? Pretty similar to an oil change then, am I right in saying that it gets filled back up with dexron 3 oil?

 

[dark_knight]

i would say dexron II or III serves just about right, unless the oilman can suggest otherwise.. and about the refilling bit, i just did it via the dipstick port coz the bay was so cramped. i'm sure there is a re-fill plug somewhere atop the transmission like on the 5MT.. you would still need a fine-tip funnel for that though..
any autobox boys reading this to give some advice..?

 

[Jay]

Either Dexron II or III will do the job mate, I took a few pics of the last one I did. Basically just drain the box using the sump and refill via the dipstick tube. Honestly can't remember how much oil was used unfortunately. I also dropped the sump and cleaned the filter and magnets of debris but it's probably a bit overkill.

Sump bung is on the underside of the box:

This looks about 3-4 litres but can't be 100% certain:

Magnet was covered in metal particles (magnet on left) but mine did run low on oil for a while:

The filter is held in with a few bolts:

A good wash with some brakecleaner cleared the gauze nicely:

That's about as far as I've delved into the autobox:

After refilling the box, let it idle up to operating temp and select each gear in turn (L,2,D,N,R & P) then check the level on the dipstick while the engine is running. That should give you a true reading of what the level is. I haven't found a 'fill' hole on the autobox just yet but if I spot one I'll let you know. In the meantime just use the dipstick tube.

Hope that helps,

Jay

 

[steve-gers]

Yeah that's spot on thanks very much guys.

 

[Paul_JJ]

The way Jay described is exactly the same as sucking it with the pump, but a lot more messy. The torque converter still has the old oil no matter what, the only way to replace it is to take the gearbox off and drain the torque converter.

Jay my manual book says that after dropping the sump you suppose to replace the filter and the gasket, did you do that? The fill hole is the dipstick -) We lucky to have one, most of the Mercedes hasn't got one at all, nor the drain plug!


My manual says that the overall amount of ATF needed incl. Torque converter is 7.2 L. The way I replace it is suck everything off with the pump (around 4 L), put a new oil in (do it slowly), then I drive the car for about 2 weeks and do the same job again, this way 75% of the fluid will be changed. I've done it 3 times when I first bought the car.

I would highly recommend the FUCHS ATF oil, you will notice a massive difference in gear changes and better fuel economy after putting that oil in.

Fuchs TITAN ATF 4400 Automatic Transmission Fluid for Japanese cars
http://www.opieoils.co.uk/p-60163-f...tic-transmission-fluid-for-japanese-cars.aspx

There is another way of doing the job, but not the safest one - you can unplug the gearbox oil cooler pipes and drain the old fluid at the same time as filling a new one, for this the car has to be in D, but it's not safe as you have to provide constant feed for the gearbox, also it would consume quite a lot of new fluid, but it's 100% fluid replacement.

Did you know that our gearboxes can be tuned? Unfortunately nobody in the UK does it, but I was able to find a gearbox tuner in Russia, who claim that he can do faster gear changes and a stall start (when you will be able to build up the revs).

http://www.youtube.com/watch?v=0dsO2jDs61U

 

[Jay]

Yeah, the Merc boxes come factory sealed so there's no dicking about with them lol.

I hit a brick wall with Toyota when trying to source a fresh ATF filter so just had to clean up the old one. It's just steel gauze so a good wash seemed to do the trick. I'd daresay the better the oil the better the results, I've got some Redline racing stuff to try so I'll report back once I've used it.

Paul's right about the ATF transfusion, wouldn't be the safest of procedures. Regular changes and good oil quality should offset the need to totally drain the old oil.

Just on the topic of stall speed by upgrading the torque convertor, has anyone ever done this with a Starlet? I can't see too many advantages outside of a dragstrip myself but it would be nice to hear of any firsthand feedback!

Jay

 

[Paul_JJ]

He said he can do it for a starlet no probs but He would need to work on the actual gearbox for some time. Not sure about the cost but affordable I think. The only problem is the postage cost due to weight! Not many people can tune auto gearboxes they're very complicated.

 

[Rev]

I have wondered about this too as a way for the auto gear box can handle bigger torque and turbo power but i'm thinking for street application in hot weather.
x2 first hand experience would be great, also does a stronger torque convertor result in extra power train losses?

 

[Jay]

Not sure on the drivetrain losses, probably has a bearing on the power low down but at full pelt the box would be fully locked down?

The thing that puts me off (other than the price!) exploring it too fair is that a higher stall speed means you need higher revs to move the car. This probably isn't a problem on the quartermile but on the daily commute it could be like driving around with your handbrake on. The box spends longer slipping as a result too so the extra heat is transfered through the rest of the box increasing wear and tear.

Worth noting that increasing engine power naturally lowers your stall speed so for the expense of upgrading the torque convertor it would be advisable to do your calculations carefully. You could end up making the car worse to drive.

 

[dark_knight]

convert to a 5MT if you are willing to go through all that trouble.. hehe

 

[Jay]

convert to a 5MT if you are willing to go through all that trouble.. hehe

I've got 4 manuals and still prefer the lazymatic for daily staging. Autoboxes are a common choice on the strip too so it's good to discuss the options!

 

[Rev]

Not sure on the drivetrain losses, probably has a bearing on the power low down but at full pelt the box would be fully locked down?

The thing that puts me off (other than the price!) exploring it too fair is that a higher stall speed means you need higher revs to move the car. This probably isn't a problem on the quartermile but on the daily commute it could be like driving around with your handbrake on. The box spends longer slipping as a result too so the extra heat is transfered through the rest of the box increasing wear and tear.

Worth noting that increasing engine power naturally lowers your stall speed so for the expense of upgrading the torque convertor it would be advisable to do your calculations carefully. You could end up making the car worse to drive.

Didn't realise the power thing , thanks Jay - Now have done some research and as usual the solution is losing weight . I am experiencing what you describe because my Sera is much heavier than the torque convertor was designed for so it takes longer to lock up as there is more resistance to the convertor locking. The stock turbo is 108.4ftlb at 2500 rpm ( 20deg C ) I used to reach this at 3000 rpm ( at 27 deg C) but have shortened the time to rev up now so lockup delay is less noticable.

I don't think I would go for a higher lock speed as I found even a slightly later lock up delay of 500prm annoying in a road car. Not withstanding I read that ' Performance converters are usually designed to accelerate more aggressively than stock, so an aftermarket converter with the same stall speed rating as stock will often be more responsive than the stock unit ' this may be a useful idea. http://www.gmforum.com/showthread.php?t=244681

So if the aftermarket convertor can lock up sooner it would be interesting to know what power increase these can give ?

 

[Paul_JJ]

Not sure on the drivetrain losses, probably has a bearing on the power low down but at full pelt the box would be fully locked down?

The thing that puts me off (other than the price!) exploring it too fair is that a higher stall speed means you need higher revs to move the car. This probably isn't a problem on the quartermile but on the daily commute it could be like driving around with your handbrake on. The box spends longer slipping as a result too so the extra heat is transfered through the rest of the box increasing wear and tear.

Worth noting that increasing engine power naturally lowers your stall speed so for the expense of upgrading the torque convertor it would be advisable to do your calculations carefully. You could end up making the car worse to drive.

I thought the same as well, but nope it's not done on the principle that the car won't move till you have 5.5K RPM - it's a modification to the gearbox to allow it to start with 5.5K RPM, but it's also starts with the usual low RPM range with no problem. And if you look at that video you can clearly see that he is holding the brakes when building up revs, but because of the low RPM limit on a standard gearbox it wouldn't make much difference if we do that on our standard gearboxes. Also it doesn't damage the gearboxes as long as it has operational temperature for the gearbox oil - for the gearbox there isn't any difference if you start with 1K or 5k RPM, it has been designed to handle 7K from the factory and it has oil cooler so it doesn't overheat - no matter if the car standing still or you drive the car.

I would be more worried about the driveshafts here -))))

 

[Paul_JJ]

convert to a 5MT if you are willing to go through all that trouble.. hehe

You underestimate automatics, they're very reliable gearboxes, no clutch in the world can do 300K miles, AUTO's do that with no problem.

Also due to the construction you have reduced wheel spin (or none at all) with an auto gearbox, not to mention the time needed to change the gear on the manual where is on the auto - if you change 5 gears on the manual would make the difference. You probably only had experience with the European Auto gearboxes - lice Merc - they're indeed very slow, never been build for responsiveness, but the comfort! In my opinion Starlets have very good response on the gearboxes, also doing 30mph in 1st gear and 70 mph in 2nd before reaching the red line - is awesome as well. Oh yeah and it's virtually impossible to damage the engine with the Auto gearboxes - it's just won't let you, as well driving the car hard on the cold engine - it won't let you do that either -)

 

[Rev]

So does anyone know an auto box upgrade that strengthens the stock box limit of 210 ftlb to say 240 ftlb before slipping occurs?

 

[Paul_JJ]

So does anyone know an auto box upgrade that strengthens the stock box limit of 210 ftlb to say 240 ftlb before slipping occurs?

Yes, this Dmitrij? Remember you spoke to him on the forum, his English is not very good. He said that the gearbox can be modified and the pressure can be increased (safely), thus allowing it to handle higher boost without slipping.