'97 M1097a2 4L80e is bad. Need advice - DIY rebuild or junkyard swap?

[gotaconvoy]

Hello all.

I've conducted diligent forum searches but haven’t found an appropriate answer. I recently picked up a 1997 M1097a2 with the 6.5l and a 4l80e. Further inspection shows water intrusion into the transmission, likely from a missing dipstick grommet. I rolled the dice and attempted multiple system flushes to no avail. The trans is done and I need advice on my next step.

I'd like to explore a junkyard 4l80e swap, but can't find a definitive answer as to which donor vehicle/year would be an exact swap, aside from the tailshaft. I believe I have the 'new' version 4l80e with the cooler lines towards the rear. I see there's some issues with the civilian TISS/TOSS rings, and If I'm going junkyard swap I want an easy swap without having to change internals or buy a new TCM. Is there an easily identifiable civilian 4l80e that is a direct swap?

If not, I intend to rebuild the transmission myself. I've never done an auto rebuild but this seems like the perfect scenario and I'm confident in my skills. Can anyone recommend a good rebuild kit and hopefully a detailed video?

Thanks all!

 

[NDT]

Anything from a junk yard will most likely need a rebuild as well.
Automatic transmission overhauls are not for inexperienced mechanics. Suggest you pull yours and shop around for what the rebuilding industry calls “bench jobs”.

 

[FlameRed]

I agree, a junk yard swap will not have the same tranny that came out of HMMWV. There are differences.

Take yours out and get it rebuilt by a local shop. That way if there are problems, you won't have to deal with shipping which is super expensive.

 

[cwc]

If there was water intrusion I would be most concerned about the valve body having corrosion issues, i.e. stuck valves. You could drop the pan and disassemble the valve body to see if it has been ruined by the water. That would be good to know before dropping it off if you go the route of having a shop do it.

Since you are confident in your skills, I would encourage you to give it a go yourself, at least tear it down and assess it. In a lot of ways, rebuilding an automatic is more forgiving than a manual transmission or transfer case.

Monster Transmission has a 9 minute video on YouTube called 4L80E Tear Down & Common Problems, which is pretty good. There are hours and hours of videos on YT, just depends on how much detail you want. I also like the ATSG manuals.

It is good to have a press. You'll need to consider special tools; a search for "4L80E special tools" turns up a nice posting on ls1tech.com with some pictures of things folks have made themselves. Probably the biggest pitfall is damaging seals during installation. Unless it is a very high mileage unit, you will probably find there is no need to replace most of the bushings and thrust washers. If you do need to replace bushings, you need proper sized bushing drivers; in the past local transmission shops have been happy to do that for me, hopefully you will find the same. You can do the teardown and assess everything, then work on the shopping list. You might find there was a simple reason it would not engage and that all the frictions and steels are in good shape. You might get by with just a soft parts kit, or just frictions without steels. It is good to get parts from a place with good support. I like Whatever it Takes here in KY, www.wittrans.com.

 

[gotaconvoy]

If there was water intrusion I would be most concerned about the valve body having corrosion issues, i.e. stuck valves. You could drop the pan and disassemble the valve body to see if it has been ruined by the water. That would be good to know before dropping it off if you go the route of having a shop do it.

Since you are confident in your skills, I would encourage you to give it a go yourself, at least tear it down and assess it. In a lot of ways, rebuilding an automatic is more forgiving than a manual transmission or transfer case.

Monster Transmission has a 9 minute video on YouTube called 4L80E Tear Down & Common Problems, which is pretty good. There are hours and hours of videos on YT, just depends on how much detail you want. I also like the ATSG manuals.

It is good to have a press. You'll need to consider special tools; a search for "4L80E special tools" turns up a nice posting on ls1tech.com with some pictures of things folks have made themselves. Probably the biggest pitfall is damaging seals during installation. Unless it is a very high mileage unit, you will probably find there is no need to replace most of the bushings and thrust washers. If you do need to replace bushings, you need proper sized bushing drivers; in the past local transmission shops have been happy to do that for me, hopefully you will find the same. You can do the teardown and assess everything, then work on the shopping list. You might find there was a simple reason it would not engage and that all the frictions and steels are in good shape. You might get by with just a soft parts kit, or just frictions without steels. It is good to get parts from a place with good support. I like Whatever it Takes here in KY, www.wittrans.com.

Thank you!! Some great information in here. Much appreciated.

 

[Autonomy_Lost]

What is the tranmission actually doing? What are the symptoms?

 

[papakb]

The first thing you need to do is pull the trans and disassemble it (or have it done) then you can make an informed decision as to what the damage is and the length you need to go to to repair it. If it's just bands and solenoid replacements on your original trans that's going to cost you a whole lot less than doing the same job on one you've bought from a salvage yard and that option is still there if necessary.

 

[thoner7]

Put in a 6l80!

 

[gotaconvoy]

What is the tranmission actually doing? What are the symptoms?

I just got the truck delivered. Before attempting to start/move it I checked all the fluids. Noticed the tranny was pink, foamy and smelled burned. Found a completely missing dipstick grommet which I suspect was the point of entry for the water. Dropped the pan, changed the filter, reassembled, filled with fresh fluid, disconnected the cooler return line at the trans and started it up. Ran about 7 gallons ATF through the system until it came out looking better. Reconnected the cooler line and tested. Have a solid reverse gear, but any forward gear is slipping horribly. Barely moves.

One interesting discovery - I found a few things on/near the trans loose such as the linkage, the carrier bearing for the front driveshaft, the missing grommet (they dont just fall out), and some other things that almost indicate the trans was out then quickly thrown back in. I wonder if a bad trans was the reason it was deadlined and the water intrusion was just a byproduct of not reinstalling the grommet?

 

[gotaconvoy]

The first thing you need to do is pull the trans and disassemble it (or have it done) then you can make an informed decision as to what the damage is and the length you need to go to to repair it. If it's just bands and solenoid replacements on your original trans that's going to cost you a whole lot less than doing the same job on one you've bought from a salvage yard and that option is still there if necessary.

Yeah, that seems to be the best course of action. I'll probably be able to dig into it next weekend hopefully.

 

[gotaconvoy]

Put in a 6l80!

Is there a direct (or reasonably direct) swap from a civilian donor?

 

[cwc]

Noticed the tranny was pink, foamy and smelled burned. .... Have a solid reverse gear, but any forward gear is slipping horribly. Barely moves.

When diagnosing slipping problems it's good to reference the clutch application chart. Transgo chart attached. If you are not getting any forward gear in any of the forward shifter positions, that points to the forward clutch not engaging. That could be because apply pressure is not being routed to it by the valve body, or the apply pressure is leaking at the shaft seals or apply piston seals, or the clutch plates are burned up. Of course, weak apply pressure will lead to slipping and burned clutches.

With the burned smell I would probably just break it all down for inspection, but if you want to troubleshoot a bit you could drop the valve body and maybe disassemble it, and try applying air to the forward clutch as described in this thread on ls1tech. There is a video link in post #7.

Rebuilt 4l80e slipping in forward gears - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - Rebuilt 4l80e slipping in forward gears - 4L80e Saturday challenge https://cimg0.ibsrv.net/gimg/ls1tech.com-vbulletin/2000x1504/70e36f7e_4361_41fc_a7cb_7d820db91a54_99941403ed85873119ba199af1575bb750f30025.jpeg . Just rebuilt my transmission during winter and just had a...

ls1tech.com

Also this thread shows some of the relevant parts, e.g. the shaft seals that can leak and reduce the apply pressure causing the clutch to burn up:

4L80E experts: overheated forward drum - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - 4L80E experts: overheated forward drum - I'm tearing down my 4L80E to rebuild and it looks like the forward drum assembly got really hot. Is this a concern? Should I replace these parts since they got hot?...

ls1tech.com

 

[cwc]

Transgo clutch apply chart.

 

[TNDRIVER]

When diagnosing slipping problems it's good to reference the clutch application chart. Transgo chart attached. If you are not getting any forward gear in any of the forward shifter positions, that points to the forward clutch not engaging. That could be because apply pressure is not being routed to it by the valve body, or the apply pressure is leaking at the shaft seals or apply piston seals, or the clutch plates are burned up. Of course, weak apply pressure will lead to slipping and burned clutches.

With the burned smell I would probably just break it all down for inspection, but if you want to troubleshoot a bit you could drop the valve body and maybe disassemble it, and try applying air to the forward clutch as described in this thread on ls1tech. There is a video link in post #7.

Rebuilt 4l80e slipping in forward gears - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - Rebuilt 4l80e slipping in forward gears - 4L80e Saturday challenge https://cimg0.ibsrv.net/gimg/ls1tech.com-vbulletin/2000x1504/70e36f7e_4361_41fc_a7cb_7d820db91a54_99941403ed85873119ba199af1575bb750f30025.jpeg . Just rebuilt my transmission during winter and just had a...

ls1tech.com

Also this thread shows some of the relevant parts, e.g. the shaft seals that can leak and reduce the apply pressure causing the clutch to burn up:

4L80E experts: overheated forward drum - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - 4L80E experts: overheated forward drum - I'm tearing down my 4L80E to rebuild and it looks like the forward drum assembly got really hot. Is this a concern? Should I replace these parts since they got hot?...

ls1tech.com

The guy "clinebarger" has a shop , the last I chatted with him, in Fort Worth. He knows his stuff on these transmissions. It would be worth your time and money to ship him a transmission to overhaul. My two cents.

 

[gotaconvoy]

When diagnosing slipping problems it's good to reference the clutch application chart. Transgo chart attached. If you are not getting any forward gear in any of the forward shifter positions, that points to the forward clutch not engaging. That could be because apply pressure is not being routed to it by the valve body, or the apply pressure is leaking at the shaft seals or apply piston seals, or the clutch plates are burned up. Of course, weak apply pressure will lead to slipping and burned clutches.

With the burned smell I would probably just break it all down for inspection, but if you want to troubleshoot a bit you could drop the valve body and maybe disassemble it, and try applying air to the forward clutch as described in this thread on ls1tech. There is a video link in post #7.

Rebuilt 4l80e slipping in forward gears - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - Rebuilt 4l80e slipping in forward gears - 4L80e Saturday challenge https://cimg0.ibsrv.net/gimg/ls1tech.com-vbulletin/2000x1504/70e36f7e_4361_41fc_a7cb_7d820db91a54_99941403ed85873119ba199af1575bb750f30025.jpeg . Just rebuilt my transmission during winter and just had a...

ls1tech.com

Also this thread shows some of the relevant parts, e.g. the shaft seals that can leak and reduce the apply pressure causing the clutch to burn up:

4L80E experts: overheated forward drum - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - 4L80E experts: overheated forward drum - I'm tearing down my 4L80E to rebuild and it looks like the forward drum assembly got really hot. Is this a concern? Should I replace these parts since they got hot?...

ls1tech.com

Great info! Much appreciated.

 

[BKubu]

There was another thread where a poster (BULLDOGGER from VA?) was looking for a transmission or considering having his rebuilt. You may want to review that thread. I suggested he contact Eastern Surplus in PA to see what they have for take out transmissions. I don't recall his response, although I believe he called them. See what they say as far as guarantees are concerned. Maybe they guarantee they are good without giving you a warranty. Not sure. I'd contact them...ask for Bill Peaslee.

(On the guaranteed good situation, I once had a dealer [not Eastern] sell me a guaranteed good take-out alternator. Well, it wasn't...and he gave me another one, but I still had to install two alternators and return the first. Not a lot of work installing an alternator, but also not the way I want to test to see if something is good.)

 

[gotaconvoy]

There was another thread where a poster (BULLDOGGER from VA?) was looking for a transmission or considering having his rebuilt. You may want to review that thread. I suggested he contact Eastern Surplus in PA to see what they have for take out transmissions. I don't recall his response, although I believe he called them. See what they say as far as guarantees are concerned. Maybe they guarantee they are good without giving you a warranty. Not sure. I'd contact them...ask for Bill Peaslee.

(On the guaranteed good situation, I once had a dealer [not Eastern] sell me a guaranteed good take-out alternator. Well, it wasn't...and he gave me another one, but I still had to install two alternators and return the first. Not a lot of work installing an alternator, but also not the way I want to test to see if something is good.)

I'll try and find that thread. Thanks!

 

[thoner7]

Is there a direct (or reasonably direct) swap from a civilian donor?

Mogman did a cool write up.

6L80 in my M998

EDIT, as you read this thread I ended up using a 6L80 as the 6L90 was toast and the 6L80 has the same output shaft as the 4L80/3L80. I was at a machine shop auction the other day and picked up a 6L90 with a MP1626XHD transfer case, it is complete with T/C, the front shaft, cooler lines and shift...

steelsoldiers.com

The 6l90 is stouter as I understand it, but the output shaft won’t mate with the stock transfer case, whereas the 6l80 does.

 

[gotaconvoy]

Mogman did a cool write up.

6L80 in my M998

EDIT, as you read this thread I ended up using a 6L80 as the 6L90 was toast and the 6L80 has the same output shaft as the 4L80/3L80. I was at a machine shop auction the other day and picked up a 6L90 with a MP1626XHD transfer case, it is complete with T/C, the front shaft, cooler lines and shift...

steelsoldiers.com

The 6l90 is stouter as I understand it, but the output shaft won’t mate with the stock transfer case, whereas the 6l80 does.

Thanks for that, it is an impressive write-up, but far more involved than I'm looking to get at the moment. Rebuilding this 4l80e is the way to go for me.

 

[gotaconvoy]

Ended up taking the overwhelming advice and dropped the trans off at a shop to be rebuilt. I'll know what we're looking at within a week.

Interestingly enough, I found out this '97 M1097A2 has the MP2225 transfer case. One of the coolant (antifeeze) lines going into it is snapped off, and I've found more loose/missing bolts that indicate this truck was slapped back together with a bunch of random parts before hitting the auction. Sure hope this transfer case is still good!