Non-Serviceable Transmission (GM)

I just purchased a car (2004 Grand AM GT) with a non-serviceable transmission, meaning no dipstick. Dumb.

Anyways, I’m going to do a trans service and replace an axle seal that has a very slight leak, but I am finding conflicting information on how to properly check the transmission fluid level and how to fill it.

There is a fill hole on the top of the transmission (accessible under the hood) and on the bottom there is a “check” plug. I’ve read that if you remove the check plug while the engine is running and the transmission has been warmed/cycled, then you should just have a tiny bit of trans fluid coming out of the check plug. If nothing comes out then add fluid. If a lot of fluid comes out, then let it as it is overfilled. This instruction was supposedly from a GM Tech manual. What a job to do at home :\

A friend told me that after the trans service I just need to remove the check plug and fill the transmission from the top until fluid comes out of the check plug. When fluid starts coming out it is full and then put both plugs back in and hit the road. I’m wondering after doing a “cold” fill like this if I need to run the car with the plugs out, cycle the transmission, and then add more fluid?

Any detailed advice from those with experience with this stupid design would be greatly appreciated. (Dealer wants $300 to do a trans service!)

I understand the car needs to be level and luckily I have access to a lift to do this job.


There is no such thing as a non-serviceable or sealed transmission. All automatic transmissions have fluid in them and all have a procedure to check and fill them.

Your transmission fluid is checked at operating temperature and running, as most GM transmissions are. At operating temperature the fluid level should be level with the check plug on the housing. Fill it through the filler at the top until fluid comes out of the plug. When it slows to a drip you’re full.


I understand, just using the “non-serviceable” term as I think it is what GM officially calls it.

But after the trans service, I would need to add some fluid to the trans before I even start the car, correct? Manual says a pan drop drains 6.9 quarts (I’ve found it to be less from experience on other vehicles), so I guess I would add maybe 4 or 4.5 quarts, then heat it up at top it off?


Many manufacturers now have transmissions with no dipstick. Toyota has gone that way for a decade now.

It costs me about $125 to have a drain and refill with my trans without a dipstick and full synthetic. I have an independent shop that I trust do it.

Yeah I found a GM tech who does side jobs; he’ll do it for $100 out the door.

I just prefer to do what I can on my own. Costs me $30 for the filter and fluid.

“But after the trans service, I would need to add some fluid to the trans before I even start the car, correct?”

Why not just fill to the check plug with the engine off, start engine, and add more until full again?

Auto transmissions are not “non serviceable”. The are just non serviceable by the average owner and car makers seem to feel for good reason. This is general posting from a transmission service advertisement. As you can see by reading, it’s just as well the average owner keeps his darn hands off the dipstick if there was one, and lets a qualified person do it. I can understand when the average owners could mess things up more then helping. So, let someone with at least a lift do it. At least, that seems to be attitude of many car makers. Many just don’t want civilians messing around in the compartment with the motor running, when, at least in my manuals it says to shut it down for every other common check which are comparably, much easier.

Properly checking the automatic transmission fluid level is not as simple as most people think. Vehicles use different procedures and even getting a correct reading can be tricky. This guide should help get accurate automatic-transmission fluid level readings.
Procedures vary from one vehicle to another

Each manufacture determines a procedure that gives an accurate reading when checking the automatic transmission fluid level in their transmission. For instance, we check most vehicles with the engine running, but we check most Honda vehicles with the engine off.

Many manufacturers have eliminated the dipstick on their transmissions and checking the fluid level requires specialized tooling and procedures. Always check the owner’s manual or service data for the proper conditions before checking the automatic transmission fluid level

@Demo-Beta If you had to ask in the first place, maybe you should not be doing it.


That’s what I would assume, but I’m just trying to make sure.

I only moonlight as a mechanic, I don’t even have a single callus on my hands normally. lol


I’ve done transmission services before, just never on “non-serviceable” setups. Again, the term “non-serviceable” is the manufacturer term and it is listed as such in the manuals. It is either that or maybe TWOADS-transmission with out a dip stick.

Is it so strange to ask about the functionality of check plug?

So screw the average person and their dipstick, come pay the dealership $100 to remove a plug and even check the status of your transmission fluid. And why would a car maker care what someone does with their own car after they purchase it?

Seems to me like this is another case where manufacturers deliberately make it complicated so the average owner has to pay to do something he/she should be able to do for themselves.

An automatic transmission, cooled off and at rest, on a level surface, the fluid is going to settle to some level within the transmission. Design a dipstick with a line on it at this level with the dipstick fully inserted. There’s your “full” level. If the fluid is lower than the line, you need to add fluid. Why does it have to be more complicated than that?

You would serve yourself to secure the factory service procedure before attempting this as a DIY job. You may need the GM scan tool to do it correctly. The link below might be of some help at least. Best of luck.

I “second” george’s suggestion. This is not something you want to make a mistake on.It’d be well worth investing in the factory manual. It’s far cheaper than a blown tranny.

And why would a car maker care what someone does with their own car after they purchase it?

Because if they screw it up out of ignorance then they are also likely to go around bad mouthing it/them.

People may grumble a bit at the expense of professional service but at least it was more likely to be done correctly and then any other issues they can identify and correct proactively while it is in for service, that’s one less potentially bad experience to contend with from a customer satisfaction perspective.

The sting of maintenance costs fade far faster than those for failures that can be orders of magnitude larger…

what does the grandamgt website say? i got a bunch of hits when i did a quick search


There are a lot of posts describing what to do around the net. I know there are a few GM techs around here and thought I’d get some clarification.

Anyway, I found a guy doing side jobs on Sundays at a GM dealership. He’s knocking out the trans service and both axle seals for $200. I’m sold.

$200 seems a good value. Good call.

Glad you found a way to get things done.

I don’t quite understand all the fuss about a transmission that doesn’t have an old-fashioned dipstick.

Every manual transmission (save for some Subarus) required you to jack up the car, crawl under the vehicle and remove a fill plug to check the level, and make a mess when filling it if needed, with gear oil running into your armpit. Honda manual transaxles had a fill plug that was so close to the frame it was almost impossible to get 10W30 in there without getting as much on the floor.

Every differential (save for for some Subarus) require you to do the same, also making a big mess when adding if needed.

Why doesn’t anyone ever complain about manual gearboxes and differentials that don’t have dipsticks?

One theory, I suspect there are quite a few manual transmissions and gearboxes on the road that have the same fluid in them for the life of the vehicle, with no obvious ill effects. That would probably be less common for automatic transmissions.

Speaking of side jobs . . .

That guy doing the sidejobs at the dealership on Saturdays must be pretty brave, stupid, or he’s cleared it with somebody high up

If you’re going to do sidejobs, don’t do them at your employer’s worksite. Not only is it in bad taste, it’s almost always in violation of the company rules

I’ve personally known guys that did sidejobs at the dealership after hours . . . and got fired for it

When I was at the dealership, the only cars I worked on were the official paying customers of the dealership, and my own personal cars. But I only worked on my own personal cars before work, during lunch, and after work