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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.

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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 '15 at 22:30
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@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. – Pᴀᴜʟsᴛᴇʀ2 Oct 23 '15 at 15:40
up vote 36 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.

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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
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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
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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. – Pᴀᴜʟsᴛᴇʀ2 Mar 14 '14 at 17:56
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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 '15 at 23:17

I know that this is an old question, but I want to provide a brief answer.

Amount of work that is necessary to fix anything inside the transmission is very close to the amount of work that is necessary to do the rebuild (on average).

Your average Rebuild = replace friction plates, and replace rubber seals (sometimes they come only in a kit) + replace and damaged larger parts (rarely happens).

So instead of saying "we will try to fix it, but depending on what we find it will cost you $1600-$3600 and your car will be here from 1 to 30 days" they say "we will put in a rebuilt transmission for $2500 and you will have your car tomorrow". On average, putting in a rebuilt transmission generates the least amount of complains from the customers. I can say this, I am just one of the customers who opted for doing the rebuild on his own and gained quite a lot of "inside knowledge"

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I hear yah. I agree with the point of putting a rebuilt transmission into the vehicle is a good way to go, in most cases. I don't rebuild (or have never tried) them myself, but will take it to a shop I trust to have it done, after I've removed the tranny myself. I've had great success with this approach. Usually costs me about 1/3 the cost of having someone else R&R the tranny, plus the rebuild (or rebuilt replacement). Thanks for the add! +1 – Pᴀᴜʟsᴛᴇʀ2 May 23 at 21:02

I'll answer this old question with very recent experience, as in still in the process of fixing a transmission to broke.

I had the transmission on my one and only car fail catastrophically. The differential broke and took out the ring gear it sits inside of. Aside from that and a couple minor things I found during the rebuild it was still a very healthy transmission worth rebuilding. The donor was a transmission I found at a local scrapyard for $225, it was the third in a set of transmissions I had attempted to drop in and drive on. Originally I was going to rebuild purely with new parts and drive on the scrapyard one in the meantime but the problems on the scrapyard ones were advanced enough that they were all on the verge of failure.

So I studied for a couple days to learn how this thing works inside-out. I had experience in the past with classic GM transmissions but never a front wheel drive, electronically controlled modern transmission. They are very different monsters. Older transmissions you can screw up and still get 100k miles out of them. These newer ones if you make mistakes you might get 100 miles or you might get 100k miles, calling them sensitive is an understatement.

I began my rebuild at around 9PM one night. I knew I would be up all night long, was well rested, had loads of bookmarks with information and a lot of caffeine ready for consumption. I had to stop at around 6AM, not for lack of stuff to get it done but I lad lost so much energy that I could no longer lift parts into place without scraping into the aluminum casing. Got some sleep, ate some food, played a game for a half hour and jumped back into it.

The entire next night was spent building it up and tearing it down, over and over again to get everything lined up just right so that the final piece would clear the case to within 0.006 and 0.012 of an inch. That's some amazing precision that can only be achieved by sheer trial and error. Very little skill factors in here, sure skill will make it go faster but your still looking at a lot of repeat work to work out all the play. This night I had spent from 4PM until 3AM getting the gear pack back in place and bolted up. The rest was fairly easy, only took an hour counting the time it took to clean the parts up.

So it was back on the road. Acted better than ever but eventually a new problem developed which I'm still working on solving. It works great when it's below 160F but once it passes 160F I loose all gears. It'll be driving along fine and then fall out of gear. There are 3 possible causes for this: the PCS has failed and shorting out at temperature, the clutch packs are burned out or the torque converter has burned out. It's not likely the clutch packs have burned out this quickly, they all looked very healthy. The torque converter might have failed, one of it's bushings has some gouging in it but the gouging isn't in any spot that would impact it's function. The PCS on the other hand is known to fail after servicing this transmission and it's advised to only be reused after testing well within spec. I didn't test the one in it but I do have one out of the donor that test as if it's brand new. I suspect the donor had it swapped since it's cheap to replace, seen no improvement because the clutch packs were burned beyond hope and then got taken in for scrap.

All in all, if I had to rebuild one for someone I would quote at least $600 for labor and probably throw an additional $200 onto labor depending on the results of an initial in-car inspection. For that price one could buy a re-manufactured transmission and have one of any very capable backyard mechanics put it on. They are relatively easy to remove and replace but extremely difficult to rebuild. The only reason I'm putting up with it is because I have no money left, not even enough for food and what money will be coming in is completely tied up by rent and bills. In other words I have no choice but to work through the problems. On the up side if I do actually manage to get it working, I found a transmission repair shop that I'm going to inquire about working at. You kind of have to become an expert to work on these things, they are very unforgiving.

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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)

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Apart from the other answers, it does happen that transmissions are not fully rebuilt. There are degrees of cost/effort. It is very common for parts to be re-used. Planetary gears, solenoids are often re-used. "Steels"/clutch pack discs are replaced. The "hard parts" (gears) may add thousands to the cost but will reduce noise considerably.

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On older cars i strip and clean off all parts replace all seals and gaskets and replace damaged / worn parts as not everyone finds it economically viable on older cars depending on its value. Also its possible the fault may be electrical on vehicles fitted with shift soloniods / speed sensors (4HP22EH/4L30E etc.

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I'm unsure as to whether this answers the question. – JoErNanO May 31 at 9:33
    
This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review – MooseLucifer May 31 at 12:42

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