Trans. Fluid Change?

[420benz]

1.What is the best fluid to use?]Brand & type]
2.What is the torque on the pan bolts?
3.What is the best way to get the fluid out of the pan without making a mess?

[Kestas]

The best fluid would probably be Mobil synthetic (pricey). But really, any trans fluid that meets Dexron III should suffice... that and 30K change intervals.

The best way to drain is to open the pan drain bolt and let the fluid out before removing the pan.

Don't forget to drain the torque converter at the same time before refilling. Draining pan and torque converter will change 85% of the fluid.

[softconsult]

Don't forget to buy a good quality trans service kit, gasket + filter. Widely available on line.

Steve

[420benz]

The pan does not have a drain bolt!
What is the torque on the pan bolts?

[deanyel]

Originally Posted by 420 benz

The pan does not have a drain bolt!

Think allen head bolt.

[softconsult]

I think it may actually be 60 inch pounds which is 5 ft. pounds. Very light and even with a 1/4 " Ratchet.

Steve

[softconsult]

There is a drain plug, but you have to crawl under there and look for it. There is now way not to make somewhat of a mess. One thing you should understand is that if your catch pan is on the ground and the car is up on jacks the draining fluid will splash all over the ground. I always try to get the pan up close to the bottom of the pan. But you will still slop some on the ground.

Sounds like new territory for you. Be careful when you wipe out pan and not leave lint or dirt behind.

Steve

[420benz]

Thanks for all of the help.I will do this next weekend.

[tvpierce]

Originally Posted by bribenz

steve; you may be right , the less the better ,i know it's not much , i've done mine several times , the first time i overtightened them of course and it leaked , now i torque them at about 8 to10 ft lbs , no leaks since,, there are spacing tabs on the pan at the bolt holes to keep you from tightening to much that you squeeze the gasket to the side or cut right through it but it's still tricky if you have not done it before ,also when you fill the transmission just put three quarts in then start it for a second or 2 , then add the rest as the fluid may come out the vent on top from too much fluid in one place , none in the converter , has this happened to any one else when filling the transmission with all the fluid at once ? ,, it happened the first time ,, never again ;;

Happened to me too.

Live and learn.

Jeff Pierce

[softconsult]

The pan bolt torque may also be different based on the transmission model.

I have only done '90 300E and '92 300E. These have no spacers and the torque is 60 inch pounds. I bought and inch pound torque wrench for that purpose, cheap on e-Bay.

When I crawled under the '97 S320, I found the spacers. This automatically puts the correct compression on the gasket. I just tightened the bolts to what felt right with 1/4 ratchet.

Steve

[Peter Fearing]

Did I miss something? I never changed the trans fluid in my '(97 ) C280, 100K miles and the trans worked fine. Think of it. Most trans changes only remove about 25 to 39% of the initial OE fluid. Trans are closed systems, so what happens to the synthetic fluid (other than a possible leak) that would require a fluid change? Oh, I also own a 30 year old Chevy Blazer. Never ( yet) changed the fluid. Have added, but the old Powerglide really works well. OK I must be a nut, right.

[Kestas]

Wear particles begin to collect in the oil. This includes clutch material and metal fines, which contaminate the lubricant. The fluid can also shear and oxidize. Any lubricant is a consumable item.

Also, modern transmissions are designed to operate on that fine edge. You won't find vehicles today that are built with the robustness that the well-known Powerglide was built with.

I'm not saying your transmissions will grenade next week from lack of fluid changes, but changing fluid WILL help with transmission longevity. Peter, I believe your transmission uses the expensive synthetic fluid, which according to MB is considered fill-for-life. Even MB has recently taken a modified (and more sensible) approach by specifying a trans fluid change at 36K and consider the transmission good for life. Most DIYers here will tell you it should be changed every 50-80K if you plan on keeping the car for a long time. The manufacturer only cares if the car lasts through warranty.

420benz's transmission has a drain for the torque converter. Like I said earlier, when drained with the pan, this will get 85% of the fluid changed. There are relatively painless DIY methods to completely exchange transmission fluid on cars that lack a torque converter drain.

[JThw8]

Originally Posted by Kestas

420benz's transmission has a drain for the torque converter. Like I said earlier, when drained with the pan, this will get 85% of the fluid changed. There are relatively painless DIY methods to completely exchange transmission fluid on cars that lack a torque converter drain.

Hope Im not hijacking the thread too much but
a) would a 300 SEL (89) have a torque converter drain?
b) could you elaborated on the painless DIY methods?

Im a decent amateur mechanic but generally spent my time under small sports cars with manual transmissions, I want to treat my new additon right though.

[Kestas]

Your 89 300 SEL probably has a torque converter drain plug. On mine it looks just like the transmission pan drain plug. It's just a matter of rotating the torque converter until it's at the bottom and recognizing it. Try searching, there's been discussion in the past about techniques.

Here's a writeup on the flush/exchange method I use for any car that doesn't have a torque converter drain:

1. Pull the transmission dipstick. Fresh fluid is translucent and cherry red. Some darkening is normal, but if it is reddish brown or mustard color and smells like burnt varnish, it is worn out.

2. Make sure the fluid is warm.

3. Remove all pan bolts except for the corners. Remove the bolt from the lowest corner, then loosen the other corner bolts a turn or two. Carefully pry the pan to break the gasket seal at the lowest corner. Drain mostly from this corner. With good technique you can avoid or at least minimize the red bath.

4. Remove pan. Inspect the pan before cleaning. A small amount of fine grey clutch dust is normal. However, if you find metal shavings, there has been transmission damage. Remove all old gasket material. Some rubber gaskets are reusable. Clean the pan and magnet with solvent and wipe dry so there is no harmful residue. Shop air can be used to clean the magnet. Hammer back any pan damage from previous overtightening.

5. (Optional) Drill hole in pan at low point and install a drain kit available from most auto supply houses. Make sure the kit protruding inside the pan doesn't interfere with anything on the transmission.

6. Replace filter.

7. Position gasket on pan. Some gaskets have four holes slightly smaller than the rest to allow four bolts through the pan and through these smaller holes to hold the four bolts and gasket in place.

8. Hand tighten pan bolts in a criss-cross pattern. After that, use a torque wrench to tighten bolts to proper ft-lbs as per manufacturer.

9. Refill the transmission using only the amount shown as “refill capacity” in the owners manual (or an equal amount that was drained), using the type of fluid specified for the vehicle.

10. You now have replaced the trans fluid and filter according to manufacturer’s requirements. Fluid is changed in the pan only.

You can stop here and go to Step 17 if you just wanted a regular drop-the-pan fluid change. For a complete exchange of the fluid (including transmission body and torquer converter) continue with the next steps.

11. Obtain the total system capacity of the vehicle from the manufacturer. Have this amount - plus a bit more - of fluid readily available.

12. Disconnect the oil cooler line from the oil cooler. Tickle the ignition to find the flow direction. Direct the stream of fluid toward a receptacle. It is better to use a clear length of hose with a shoplight laying next to it so you can see when all the old fluid has left the system.

13. Start the engine, let it idle to pump out old trans fluid until you start seeing air bubbles.

14. Stop the engine. Refill transmission through fill tube with fresh fluid - same amount as pumped out (usually about 2-3 quarts).

15. When either the fluid color brightens or the total capacity has been replaced, shut the engine off and re-attach the oil cooler line. All trans fluid has now been changed.

16. Button everything back up. Clean up the mess.

17. Recheck the fluid level. With the car on level ground, set the parking brake and the transmission in Park or Neutral. Let the engine idle for a few minutes. Shift the transmission through all detents, pausing momentarily at each position, before returning the lever to Park or Neutral. Check the fluid level again and check for leaks. Refill fluid so it is slightly undercharged. This way it can be properly checked and topped off after a long drive.

[Hirnbeiss]

It's exactly the same for the earlier models, except:
1. They have dipsticks
2. They use Dexron II/III
3. No song and dance about getting temp to 80C and filling to the rim (with Dr. Z's profit formula)