C63 AMG (W204) 2008 - 2015

General automatic transmission question

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Old 01-21-2016, 09:25 PM
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C63 AMG P30 *EuroCharged*| Porsche Cayenne | Buell XB9SX
General automatic transmission question

Nvm

Last edited by m a x i m u s; 01-21-2016 at 10:33 PM.
Old 01-21-2016, 10:45 PM
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2009 C300, 2002 Honda S2000 Turbo, 1994 CBR 600 Streetfighter, 1999 Ford F350 Diesel
Originally Posted by m a x i m u s
First, this isn't about my C63. I'm not familiar with auto boxes so here's my question: If my transmission fluid is very low and the gears start slipping and shifting funny, is it true that the whole tranny needs to be rebuilt? Can't you just replace the parts affected? Or is it case by case kind of thing?

I am no transmission expert, but past experience tells me that there are a number of factors at play which you will want to narrow down first.

Vehicle mileage, duty level, last service date and transmission model differences can indicate the brst course of action.

I'd suggest first adding fluid to the proper level to see if that helps.

Automatics typically are very reliant on the correct fluid pressure. This pressure is created by the pump and forced into different valves and paths in the valve body based on gear selection and conditions. Low pressure from lack of fluid or a failing pump could definitely cause slippage.

The next thing to look at (especially if high mileage) is to drop thrle transmission pan and check how much material is on the magnet. A lot of material could mean the clutches are toast from excessive slip.

Note that if very high mileage, it is generally recommended that the fluid not be replaced/flushed as the clutch material and metal flakes in the fluid can sometimes be the only thing allowing the transmission clutches to continue to grip.

Domestic vehicles, especially heavy duty trucks will often have clutch rebuild kits in the couple hundred dollar range. Not sure what vehicle you are working on though.

If the slip only happens in certain gears such as a delay to reverse and 3rd, or slipping only in forward gears, you may be able to narrow down the specific part or clutch pack that is bad.
For instance, in my F350 diesel, a slip or delay when engaging reverse or 2nd(?) Indicated a bad fluid pump. But if it slipped to first, the forward clutch set was bad.

Another note- heat is a huge enemy of automatics, so i dont not advise you drive on a slipping transmission for fear of further damage.

If you have OBD2, you can also use a bluetooth dongle with the "torque" android app for some live stats. It was able to show slip ratio and torque converter lockup on my truck, along with a plethora of other useful sensors.

Anyways like i said, I'm no expert. These are just things i remember from troubleshooting some of my prior vehicles and helping friends and family. I hope this at least gives you a general idea of what to look for.

Good luck!
Old 01-22-2016, 12:28 AM
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Thanks a lot for the info. I think I really messed it up, though, bc I drove it for a few miles, seemingly with low fluid bc it was leaking as I found out later. I think it's toast...

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