Sign up ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.

I am old enough to have had about four transmission failures spaced over about 40 years and at no time did any mechanic ever offer to “fix” it; the only diagnosis has been a complete rebuild.

This is not what happens to any other part of the car. There are many potential repairs to the engine. Various individual parts can be replaced and/or repaired and even the engine itself can be tinkered with to an amazing extent without ever costing anywhere close to $2500. I’ve even heard of having engines rebuilt for less than that.

Not transmissions though; only a rebuild. I’ve asked every mechanic I’ve ever used why and I’ve gotten many different answers – they usually involve something about the transmission being so hard to get to that by the time you’ve hoisted the engine out of the way or done whatever else, you’ve spent enough labor to make it feasible to just rebuild the whole thing.

But this doesn’t really ring true for some reason. I can’t see why a manufacturer can’t design some access into the thing that might allow some service. That last mechanic told me that the case and all the gears inside are all original – they only replaced the parts (clutches) that were worn. Surely some sort of access hole could be a part of the design much like the oil pan underneath the engine. My current vehicle's transmission has no drain plug at all that I can see.

share|improve this question
Old question, but: automatic transmissions suck. (And not because I prefer manuals.) A modern, from-scratch implementation would be a manual with a hydraulic shifter and computer-operated clutch. Manuals are intrinsically simpler and easier to repair - it makes much more sense to automate the interface rather than the internals. So, why do we make them still? History, and unions. – David Lively Sep 25 at 22:30
@DavidLively - I would disagree with you. The main reason for automatic transmissions are still in use is ease of use. Regular operator engaged manual transmissions are much harder to use from a driver's standpoint. And as for hydraulically shifted manual transmission, these are being made today, both as OEM and aftermarket systems. And don't forget CVTs as well. – Paulster2 Oct 23 at 15:40

2 Answers 2

up vote 19 down vote accepted

This is one of those things which are easier said than done. To start with, let me show you a picture of a four speed transmission which has been blown apart:

enter image description here

All of those hundreds of parts go through the front end of the transmission. If a single part is bad (which it usually is not the case), you have to pull all of this apart in order to diagnose and repair. Like the mechanic you talked to said, it doesn't make sense to replace just the part which is bad while you have it all apart. The parts are pretty much the cheap part of the rebuild (or fix). Why not just make it a brand new transmission through the rebuild process. You could replace the single part, at a cost difference of a couple hundred dollars, only to have it go bad again in the not too distant future when another part goes bad which wasn't replaced.

In most cases when a transmission needs repaired, it is one or more of the soft parts which have gone bad. These include the band(s) and clutches. Usually the hard parts, like the gears, do not go bad and are reused after a thorough cleaning and inspection. You also have to consider, the transmission is very susceptible to debris. When these soft part start letting go, it can put a lot of debris through the transmission which the filter cannot keep up with. When the debris starts going around, it will damage other soft parts in the process. Soft parts also tend to wear at about the same pace (within the same group). So, not just one clutch in the clutch pack will go bad, but the entire group of them will go bad. You aren't going to replace just one clutch, you have to replace all of them. One last thing to consider here is that they sell the transmission parts as a kit (with a few exceptions). You aren't just going to buy single parts. By parts in this instance I'm talking about the soft parts ... you can usually buy hard parts separately.

There is no other way, with current transmission design, for you to get at any of the parts inside the transmission ... at least the parts which make the vehicle go. The design as it is, is very compact and does the job very well. If there was any way for a mechanic to be able to get to the parts inside without going the way it does now, it wouldn't have the strength to stay together. Believe me when I say, you could be a rich man to design an automatic transmission to do as you are suggesting and still have it as compact and efficient as what is currently offered.

The reason you don't see a drain plug on most automatic transmission is because when you change the fluid, you also change the filter. The exception to this is when you take it to a shop and get the transmission flushed. When they do this, they force fluid backwards through your transmission using the cooling lines. This (supposedly) cleans the filter in the process as well as completely exchanges the old fluid for new fluid (to include the torque converter - which doesn't happen when you just drop the pan).

The reason for the cost, as you suggested, is because of one, the labor involved in removing the transmission from the car, and two, because not every mechanic can rebuild a transmission. To do it right takes some extra learning. You just cannot throw it together and expect it to work ... and every make/model is different. All of that costs money. Most engines, on the other hand, are pretty much the same (with a few exceptions). They are all pretty much hard parts which go together relatively easy. There are some idiosyncrasies, but for the most part, they're not a big deal.

I hope this gives you a flavor for why you aren't going to see too many shops offering to repair your transmission. Again, as the mechanic said, the major part of any transmission repair is the labor for Removal & Replacement of the transmission itself.

share|improve this answer
Labour is almost ALWAYS the deciding factor with these things. Even something as stupid as replacing a cheap bulb behind the speedometer requires about 30 minutes to 1 hour of labour, so it's $1 for the bulb and $20 to $40 to put it in. It sucks, but it's true. – Juann Strauss Mar 14 '14 at 10:08
Thanks for your well constructed answer. My question reads sort of like a rant so my apologies. I've been thinking and in my adult life, I've owned 11 vehicles of which three have had to have transmissions rebuilt. I suppose this isn't too bad considering that of those three, I never had the fluid replaced. If I understand your description though, even that won't make one last forever. – glw Mar 14 '14 at 12:47
An automatic transmission is a give/take solution. You have clutches/bands (soft parts) which wear out, so the expensive parts (gears/planetaries) won't. It's the same principle as a standard transmission, thinking of the clutch. At least that's the way it's supposed to work ... sometimes it doesn't quite do that though. – Paulster2 Mar 14 '14 at 17:56
On a related note, if one part failed after 120,000 miles, even if all the other parts would be good for another 40,000, replacing just the failed part would mean the transmission job would only "last" 40,000 miles. Even if a mechanic could identify and replace only those parts which would fail within the next 40,000 miles, replacing everything wouldn't cost much more money but would likely make the repair "last" more than twice as long. – supercat Feb 22 at 23:17

Every vehicle owners manual tells you the frequency at which your auto-trans should be serviced/adjusted.Very few do hence things go wrong.Hate to sound like your nanna but ppppp (proper prevention prevents poor performance)

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.