A343f reverse failing?

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Vudu77

Vudu77

Joined
Aug 21, 2016
Threads
1
Messages
10
Location
San Diego, CA
Do I need a new (used) A343F? This only happens in reverse under load. All other gears function flawlessly. 97FZJ80 with 250k mi. Transgo shift kit installed. Vibrations are felt worst in transfer shifter. Already flushed and no evidence of metal in pan. Any suggestions?

 
I can't really tell what the problem is from the video, but I assume that Reverse gear is slipping?

How long ago was the Transgo kit installed and who installed it?

A couple of questions for you:
First, was the fluid level correct?
Second, when you say flushed, do you mean you exchanged the fluid in the entire cooling loop, or did you drain the pan and refill it?
Third, have you checked to see whether there are DTCs for the tranmission or not?
Lastly, does this happen when shifting from Park to Reverse and Neutral to Reverse, or only one of the two, and if so, which one?

These are the first steps in troubleshooting. You may not find the root cause of the problem after these steps, but you may find information that will be useful later.

If it's only Reverse, (best case) it's most likely a worn 2nd coast brake band. This is unusual, unless the truck has been used to pull loads in reverse, which you should never do, unless you just want to see how quickly you can destroy your differential, but it's not beyond the realm of possibility. Worst case, you'll need other parts, which aren't available from new stock anymore.

Unfortunately, the only way to determine this is to remove the transmission. It doesn't have to be torn down, but the pan does have to be removed to check the function of the brake band. If the band friction lining is worn, you will have to disassemble the transmission to replace it. At that point, you might as well replace all the seals and clutches, because they're already out of the case. You don't have to though, and a function test for the other gears is available when you test the brake band, so you'll know before you tear it down whether they have to be replaced or not.
 
Malleus said:
I can't really tell what the problem is from the video, but I assume that Reverse gear is slipping?

How long ago was the Transgo kit installed and who installed it?

A couple of questions for you:
First, was the fluid level correct?
Second, when you say flushed, do you mean you exchanged the fluid in the entire cooling loop, or did you drain the pan and refill it?
Third, have you checked to see whether there are DTCs for the tranmission or not?
Lastly, does this happen when shifting from Park to Reverse and Neutral to Reverse, or only one of the two, and if so, which one?

These are the first steps in troubleshooting. You may not find the root cause of the problem after these steps, but you may find information that will be useful later.

If it's only Reverse, (best case) it's most likely a worn 2nd coast brake band. This is unusual, unless the truck has been used to pull loads in reverse, which you should never do, unless you just want to see how quickly you can destroy your differential, but it's not beyond the realm of possibility. Worst case, you'll need other parts, which aren't available from new stock anymore.

Unfortunately, the only way to determine this is to remove the transmission. It doesn't have to be torn down, but the pan does have to be removed to check the function of the brake band. If the band friction lining is worn, you will have to disassemble the transmission to replace it. At that point, you might as well replace all the seals and clutches, because they're already out of the case. You don't have to though, and a function test for the other gears is available when you test the brake band, so you'll know before you tear it down whether they have to be replaced or not.
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Malleus, thanks for the reply.
-Yes, the video is supposed to show reverse slipping with brake pressed.

- quick revision to the history: I've owned it for about 10 years and noticed it a few years after I purchased it (it may have existed before and I never noticed it). I installed the transgo shift kit about 5 or 6 years ago in an attempt to fix the issue with no change in symptoms. Same with the complete flush. I have never towed anything with it and I'm pretty sure the previous owner didn't either.

- the issue is only in reverse under load and she drives fine as a daily driver. I just avoid backing up hills or going off-road. It also has not gotten any worse.

-Fluid level is correct and entire cooling loop was flushed.

- I use an OBD app to monitor vitals and haven't seen a DTC pop but I have not specifically looked for one. I'll check on this.

-The slip occurs when shifting to reverse from both park and neutral.

-I've been over the TSB reverse slip threads and from what I can tell my serial number doesn't fall in the affected ranges.

Im good with doing most of my own work. I can drop the trans and pan and do testing but I wouldn't attempt to crack one open. Any good references for checking the brake band and function testing?
 
First, I want to make sure I understand your problem correctly. The transmission slips in reverse when your foot is on the brake? I'm confused. I have a '94 that slips in reverse, but only when I goose it. When I idle in reverse, or even just apply a slight throttle, it's fine. My problem is very different from yours, however (different tranmission altogether).

I would expect the slipping to occur when you are in reverse and applying throttle. I guess if the friction lining was really toast, it'd slip in reverse when you're holding the brake, but I've never thought about that.:hmm:
 
The troubleshooting section of the vehicle service manual (1997 is RM510U) is in the Resources section, 80s forum, if you don't have one. Unfortunately, Toyota, in their infinite wisdom, steadily pared down the information in the 80 series manuals as the model aged out. The 1994 manual has the most information in it, but that model, as I said, had a different transmission than the 3rd generation (1995-1997) in the US.

Fortunately, the first year the 80 series was delivered with a A343F transmission, 1995, has that year's service manual (RM432U) with a lot of good to know information in it. I'd recommend you download that one too. Same transmission, same engine, but apparently Toyota thought the dealers would actually be working on transmissions in 1995.

Using the 1995 service manual, start with page AT-34. That'll get you up to speed with how to get the transmission DTC(s), if any. Your OBDII reader won't get them; you have to use the method in the manual. DTC explanations start on page AT-42 and run through page AT-45. You can try the mechnical troubleshooting procedures (pages AT-46 through AT-55), but unless you have access to a bench full of pressure transducers, you'll have to forego the hydraulic test (this is the on vehicle operation test, not the one I mentioned in my first post).

There is a matrix of problem symtoms for troubleshooting, (pages AT-61 through AT-67) which might be helpful to you for general knowledge. You will need the unit repair manual (also in the Resouces forum, 80s section) to do the function tests for the individual section operations. Make sure you get the 80 series A343F manual and not the 100 series A343F manual. Same transmission family, not the same transmission.

I think, if you haven't torn into an automatic transmission before, you should use the general service manual as homework before you open the unit repair manual. Not necessary per se, but I think you'll get more out of the unit repair manual if you have the general service manual to build on.

IMO, if you are comfortable pulling the transmission, you can easily handle removing the pan and valve body. You'll need a workbench at least 2'x4' (actually this is the size of my transmission bench and it's plenty big enough), and a large pan to catch errant fluid. I use a FloTool aluminum pan
1765763596194.webp

highly recommended. Also, you need a way to stand the the transmission up on the output shaft, so that you can face the bottom side of the transmission for the tests. In a pinch, you can use a plastic milk crate with a hole in the bottom, turned upside down. It's actually almost the perfect height (it is for me on my roller seat). I actually have a holding fixture (it's bolted to a corner of my large workbench), but I use two milk crates, stacked, under the output shaft, just for insurance sake.

The service manual says you need a holding jig, similar to an engine stand, but you can get by without it, if you're not tearing the unit down and rebuilding it. All this will make sense when you read the manual (it's full of pictures :))

All you need for the tests are steel scale/caliper, compressed air and a rubber tipped blowoff nozzle. You'll need some FIPG to seal the pan when you're done, too.

BTW, both copies in the Resources forum are bookmarked, but the 1995 version has a more robust set of bookmarks. I use that one the most, so it's a little better edited than the others.
 
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Also, I'd recommend you resist the temptation to split the valve body in two and look inside. Bad things happen when those ball bearings fall out because you split it open with the wrong side facing up. Ask me how I know.
 
Malleus said:
First, I want to make sure I understand your problem correctly. The transmission slips in reverse when your foot is on the brake? I'm confused. I have a '94 that slips in reverse, but only when I goose it. When I idle in reverse, or even just apply a slight throttle, it's fine. My problem is very different from yours, however (different tranmission altogether).

I would expect the slipping to occur when you are in reverse and applying throttle. I guess if the friction lining was really toast, it'd slip in reverse when you're holding the brake, but I've never thought about that.:hmm:
Click to expand...
The slip only occurs when pressing the brake and applying heavy throttle when in reverse. It's fairly consistent but more prominent when it's warm.

Thank you for the detailed breakdown! I sincerely appreciate the guidance. I'll source the downloads and start doing homework.

Assuming it's a friction lining or the 2nd coast brake band you previously mentioned, I guess the fix is a complete tear down to replace the components (if they are available)? I've taken it to a few shops who wouldn't even look at the rig due to its age. Any ideas on a way forward? Ive dropped the valve body to do the shift kit but I don't have the tools or experience to crack it open. Rebuilt units are non-existent from what I can see. Better to try a used unit off eBay or other source?
 
So, that makes sense. This is actually one of the mechanical tests. You'll see that in the 1995 service manual.

If the coast brake band lining is worn, you can just replace that. It's midway down the case, so you don't have to tear the entire assembly apart. You do have to pull the overdrive and direct clutch assemblies (and put them back in later, obviously) to get it out, and that's the worst part of the job, IMO.

Common wisdom is that if you're going to the trouble to open the transmission, you might as well do everything that can be done, because it's not a trivial exercise. Having said that, there's no reason not to fix only what is failing now. The downside is you'll have to be back in there at some time in the future; when that is depends on the current condition of (primarily) the friction linings and the use the truck sees.

There are aftermarket kits, from all major transmission parts suppliers, Transtar, Transtec, Sonnax, Sun. Most use Raybestos clutch discs. They come in three flavors: overhaul (seals and O-rings ; pretty much a waste a money), banner (no steels), master (with steels). FWIW, I'd be very surprised if, after you invested the time and money to open the case, replace the parts and reinstall the transmission, that you'd get another 30 years of service if you used aftermarket parts.

Parts are still available from Toyota, although the rebuild kits, for some reason, are not.

Aftermarket kits, from what I've seen, run about $200. Toyota parts will be about twice that, not including shipping and tariffs.

I can provide you with a list of the parts which was in the overhaul and rebuild kits, if you want to use Toyota parts. Most of the online parts sellers can get them. My recommendation would be to contact Dave Stedman at Japan4x4.com and buy what you need from him. At a minumum, I'd recommend replacing the seals and O-rings, as well as whatever friction lining parts need to be replaced, as indicated by the current operating failure.

Also, a final thought: common wisdom is to replace the torque converter with a rebuilt transmission. The thinking is that you can't test them, only a TC rebuild shop can do that, and you can't clean them, so anything left in them will make its way back into your new, spotless transmission. An aftermarket TC will set you back between $350 and $500. There are no new units available and the aftermarket units are rebuilt Toyota units.
 
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Malleus said:
So, that makes sense. This is actually one of the mechanical tests. You'll see that in the 1995 service manual.

If the coast brake band lining is worn, you can just replace that. It's midway down the case, so you don't have to tear the entire assembly apart. You do have to pull the overdrive and direct clutch assemblies (and put them back in later, obviously) to get it out, and that's the worst part of the job, IMO.

Common wisdom is that if you're going to the trouble to open the transmission, you might as well do everything that can be done, because it's not a trivial exercise. Having said that, there's no reason not to fix only what is failing now. The downside is you'll have to be back in there at some time in the future; when that is depends on the current condition of (primarily) the friction linings and the use the truck sees.

There are aftermarket kits, from all major transmission parts suppliers, Transtar, Transtec, Sonnax, Sun. Most use Raybestos clutch discs. They come in three flavors: overhaul (seals and O-rings ; pretty much a waste a money), banner (no steels), master (with steels). FWIW, I'd be very surprised if, after you invested the time and money to open the case, replace the parts and reinstall the transmission, that you'd get another 30 years of service if you used aftermarket parts.

Parts are still available from Toyota, although the rebuild kits, for some reason, are not.

Aftermarket kits, from what I've seen, run about $200. Toyota parts will be about twice that, not including shipping and tariffs.

I can provide you with a list of the parts which was in the overhaul and rebuild kits, if you want to use Toyota parts. Most of the online parts sellers can get them. My recommendation would be to contact Dave Stedman at Japan4x4.com and buy what you need from him. At a minumum, I'd recommend replacing the seals and O-rings, as well as whatever friction lining parts need to be replaced, as indicated by the current operating failure.

Also, a final thought: common wisdom is to replace the torque converter with a rebuilt transmission. The thinking is that you can't test them, only a TC rebuild shop can do that, and you can't clean them, so anything left in them will make its way back into your new, spotless transmission. An aftermarket TC will set you back between $350 and $500. There are no new units available and the aftermarket units are rebuilt Toyota units.
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Thanks again for the advice. I might as well take a swing at it but I have a lot of homework to do prior to starting. If I'm gonna do it, I'll be sourcing Toyota parts. I will definitely reach out once I begin.
 
Known issue. I posted the tech pubs a few decades ago.

There was several mods from the factory and your best bet is to find a used transmission built in late 97 as it’s your best bet to getting all the mods.

If you dig up those posted tech pubs they have serial numbers associated for when the mod was installed.
 
Is this the TSB you're referring to?
1765896876980.webp
 

Attachments

1765896959654.webp

1765896982630.webp
 
1765897031013.webp
 
@Vudu77 if your transmission is in this serial number range, you already have these modifications. If it's not, given the mileage you have, I'd hazard a guess that these would only help once you rebuilt the transmission.

FWIW, if you wanted to make just these modifications, you're looking at a full rebuild. All of the pars listed, except the brake spring return assembly (the disk with the several little coil springs on it) and the valve body piston spring would be include in a new gasket kit. I would not expect them to be in any aftermarket kit. Those parts are listed in the catalogs, but I haven't seen them available (from aftermarket stock) for a very long time.

I wouldn't open a case just to do this, and leave everything else as I found it. I wouldn't have any faith in a transmission shop that would either.
 
The thread from days gone by with the discussion about transmission slippage is here.
 
As a general interest rider to this thread, here's a sample site for TSB's: CarComplaints.com

I love the disclaimer at the top of the page:
1765901692764.webp
 
landtank said:
TSB breakdown:

Starting with serial number 96JE-06161, the B3 brake return spring assembly and low coast modulator valve compression spring was updated.

Starting with 97AE-07106 the material of 3 O-rings where changed to help them seal better.

Then serial numbers 97H*-00001 thru 97K*-99999 need to have the check ball added to the valve body.


Look at your serial number and plug it into the serial ranges above.
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Holy crap, got it on the first try
 
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