Advice from the maintenance and repair experts, please

[legendaryandrew]

Or anyone with insight haha. My 03 suburban appears to have a slipping transmission. 4l85e behind an 8.1. Twice now it slipped in 4hi, once it got warm enough for the info reader to indicate it was getting hot. Drives and shifts fine, shop says it isn't throwing any codes, but that the fluid was burnt smelling.

They're telling me a rebuild is imminent, and I don't doubt them, but here comes my questions. 130k on it, known to be a reliable transmission, I know **** happens, but is it possible it just needs a fluid flush? Is there an noninvasive way to know for sure? And last but not least, how long until it's at a critical level considering I pretty much only use it for camping once to twice a month with light wheeling? Thanks guys!!

 

[fiddypal]

I was always told never to flush(power flush), just drain and replace fluid or drop the pan and drain it that way to get most out. When replacing make sure to use the exact factory fluid if possible, I've heard mixing fluids on older cars can cause a film to build up because the two fluid types don't mix completely and that will cause new issues.

With that many miles some new fluid would be the first place I start before writing the entire trans off for a rebuilt.

 

[AFBronco235]

I agree a simple fluid change, and NOT a flush is all you need. (A flush is actually less affective because it leaves a LOT of deposits behind. If possible, drop the pan and wipe it out.

I would also recommend you install an oil cooler if it does not already have one. I don't know much about chevy transmissions, but if its overheating, then it needs some sort of external cooler plumbed into it.

 

[rayra]

Often seems to be that a flush is about the worst thing you could do, at this point. That cruddy fluid is what is keeping it working. Best stopgap I know is a partial fluid change, using a trans fluid formulated for high mileage vehicles. It's modified a bit to help give a better grip.
Some trannies a band adjustment is possible, but once you do that much surgery you might as well do the full rebuild, the cost difference isn't much more at that point.

http://lucasoil.com/products/transmission-products/lucas-transmission-fix

Again, these are a stopgap solution, not a repair. Start budgeting / shopping for your transmission rebuild / replacement.

 

[TXscout]

I agree, stay away from a flush. If you haven't done an annual flush since the birth of that transmission, it is a risk not worth taking. Drain fluid and replace (not familiar with the filtering on that transmission, but that should be addressed) and cross your fingers. Also, if you do need to go down the route of a new/rebuilt tranny, do extensive research and spend your money on something with a great warranty that will take some abuse. I can't tell you how many customers of ours have been burned by transmission rebuilders who don't know what they are doing. It is a dying art and not many good techs are left.

 

[Burb One]

Agree with the drain and not flush.

I have never been a proponent of those "snake oil" remedies, but I had a beater that was worth less than the transmission when it started slipping. I put a bottle (in the 4l85e, probably need two bottles) of that Lucas "stops slip" in it and got another 15k miles out of it before it slipped again, amazing for 10.99. Not sure if this will carry over to your truck. Also, with that car, I was always in AAA distance, but for a truck I am bringing to a remote place, I don't know if I would have done the same.... but if it gets you by until you can get it rebuilt, might not hurt for the price.

ALSO for ANY transmission, (especially for one as commons as the GM 4Lxx series), either go to the $$$ nationwide drag racing "name brand" rebuilds- (RPM, monster, etc.), which will cost $$$ but be bulletproof- think of it as an upgrade and will have a warranty), OR go to a local guy, who ONLY builds 4lxxe. The Gm 4 speeds, are common enough in general, but especially for fleets, that there is someone locally who rebuilds ONLY THEM. IE you want to guy who is looking at 4l6/80e's all day, everyday and knows it like the back of his/her hand. What I did, was the last time my utility guy came around, I asked him for their fleet mechanic's number, and I asked him who he sent their GM vans to for transmissions. Found a guy, who only rebuilds 4l60e's. I've been going 5 years strong on that trasnmission, which lasted longer than any of the GM stock ones. I will eventually upgrade my 4l60e to the 4l80e when this one hits the hay..... your 4l80e, should have lasted forever..., maybe a bad history? Also, any good transmission builder will give you, at least a, 1 year no questions warranty.

 

[legendaryandrew]

OK thanks for the info guys, I really appreciate it. My dilemma now is, I get buy a new heavy duty trans from gm (new new), for 2900, and source my own torque converter, or find a builder locally (already got a quote for 5700, built trans, and added cooler, not sure of companies history tho).

 

[rayra]

$5700!! Holy crap that's about 4x the price I would have expected. Seriously, that's a ripoff. You can buy an entire hi-mileage Suburban for that price. I literally paid $6000 for my '02 Z71 with 116k mi, 18mos ago and it's in very good condition overall.

And you can buy the factory cooler and lines for ~$250 at rockauto.com. It's a simple install.


eta - Monster wants 'only' $2k for a solid rebuilt 4L80E for 4x4. You can swap it in a day with just a little wrench experience and a few basic tools.
http://www.monstertransmission.com/4L80E-Transmission-Super-Duty-Performance-4WD-4x4_p_5236.html

 

[tgreening]

My experience with slush boxes.....

Driving down the road fat dumb and happy...VrrrrrROOOOOM!! Sound of engine high revving because the tranny decided to suddenly fly south and essentially disconnect itself from the drivetrain.

IOW when they finally decide to go they tend to go with little real warning. If I were driving a commuter and staying close to home or within that AAA distance I might try some of the "snake oil" treatments to wring a few more out of it. If you are counting on this ride to get you to points unknown and back, without fail, then you are asking for an eventual Bad Weekend by going the bandaid route.

And sweet Jesus, who wants $5,700 to do a rebuild?

 

[1stDeuce]

I wonder if you might change something you're doing to make it a little happier also... You say it slipped in 4 hi, and that once it was also hot enough to get the warning. And the fluid smells burnt. That suggests to me that you could be "abusing" the transmission in one way or another....

I don't know the circumstances, but the 8.1L makes a LOT of torque, and if you're asking the truck to do something in 4 hi that's taking advantage of all that torque, and really working the torque converter for extended periods (Like foot to the boards in sand or heavy snow) you may need to think about using 4-low. Using low range takes a lot of load off the transmission.

Modern trans fluid is pretty good stuff, but if it's not been changed much, and it's burnt smelling, it's past time. If you've only noticed an issue when you were running it pretty hard, it's probably not too late... Step 1, as pointed out above, is a fluid and filter change. Not a flush, just dump the pan, swap the filter, and toss new fluid in to bring it up to the proper level. Drive it and be nice to it for a while, and if it seems OK, you might repeat the process of drain and fill again, but skip the filter.

You should also be aware that the "Trans HOT" warning usually comes AFTER you start cooking it, not before. If you see temps getting up past 250, you need to rethink what you're doing. By 300, you're cooking it. Usually about 330 is where the fluid starts getting black and stinky pretty fast...

I suppose it might also be worth a check to make sure the trans cooler (Right in the center, behind the grill) isn't filled with mud. Rinse that sucker out! If you do a lot of puddle splashing, the dirt will accumulate and plug the coolers off fairly effectively... A simple rinse usually restores air flow through them. (Radiator, condenser, and trans cooler all should probably be rinsed as well as possible...)

Good luck!!

 

[legendaryandrew]

Quick question, my boss mentioned maybe it's the tcase as its only happened in 4wd? It's the np246, which does have the viscous coupler....

 

[rayra]

Shouldn't have anything to do with the output shaft / driving of the rear axle. That portion keeps doing what it was doing, when the transfer case clutch is engaged to drive the front axle.

However, the increased load of driving all four wheels could easily make the difference in the drive bands slipping in the transmission. Especially on dry pavement.

And frankly that viscous coupling is supposed to slip, under certain conditions. It's what it is there for. To keep your transfer case from blowing up.

 

[Martinjmpr]

Dumb question perhaps but I thought all the 2500's had trans temp gauges (to the left of the tach.) What temps have you seen on that? I monitor trans fluid temp using my Scangauge and the highest I've seen it is about 210. That's pulling a 2,000# trailer up a 7% grade at 11,000' in mid-Summer (Berthoud Pass.)

 

[PGW]

Quick question, my boss mentioned maybe it's the tcase as its only happened in 4wd? It's the np246, which does have the viscous coupler....

NP246's use a series of friction plates to simulate AWD/full time 4WD but it is not a true AWD case and has no viscous coupler. But I don't think this is a T-Case problem anyways. In 4WD there was probably more load on the transmission. I would drop the pan (my 8.1L Yukon XL already had a drain on the trans pan, not sure if yours does too) and check things out. Just throwing blind darts but maybe your cooler or cooler lines got crapped up with something and wasn't flowing as much as it should causing it to get hot.

 

[legendaryandrew]

It sits at nominal temp all the time, except that one time it started overheating, and even then the gauge never got to the overheatED line.

Dumb question perhaps but I thought all the 2500's had trans temp gauges (to the left of the tach.) What temps have you seen on that? I monitor trans fluid temp using my Scangauge and the highest I've seen it is about 210. That's pulling a 2,000# trailer up a 7% grade at 11,000' in mid-Summer (Berthoud Pass.)