Risk of running it?

[stukreit]

Truck is a 1997 K2500 Suburban, 6.5TD, 4x4, 4LE80, 160k miles, very little towing, mild climate. Many years ago
I put on a very stout aftermarket transmission cooler system.

I often put the shifter into 3 or 2 around town just to take a load off the brakes. Gentle but firm with the
shifter and throttle, no need to make the 6.5 scream over 2600rpm.

The transmission has had one or 2 very mild indigestions in the past 500 miles,
eg "Hmnn, that shift felt a little rough"

Last week it had a more major event. At highway speed, the speedometer started going a little haywire, then it started slipping about 10%. We could keep up with traffic but the engine rpms were sliding up. Pulled into the nearest service station, followed instructions for properly measuring transmission fluid level, found it to be low.
It took about 12 oz to bring it up to midpoint. The fluid doesn't smell burnt. We were able to complete 400
miles in the Sierra over the next few days including 4wd in snow for 60 miles. Has been fine for another 100 miles around town lately.

So I'm in THAT position of replacing fluid and filter and any easily reached solenoids etc. I'm happy to do that, do a better job of watching the levels, and keep driving it. Last week's event was a wakeup call but not
catastrophic. Not a big deal to include transmission fluid in the in-car toolbox.

My questions are: Are there ways to road test or scanner test the transmission for other problems, possible triggered by the low fluid level?

I need a test that gives confidence that its not going to fail more disastrously in the next (coupla) 1000 miles.

 

[Twisted Steel Performance]

I don't know the answer to your question, I don't think their is a test but I could be wrong..

What tranny fluid are you using?

I offer a fluid that has healing quality's and is very different than any other on the market. I can't say it would fix it if it is truly on it's way out but it could help cure and slick things up inside..

https://twistedsteelperformance.com...yn-automatic-trans-fluid-gallon-bottle&page=2

 

[THEFERMANATOR]

3 quarts would be low, 12 onces is less than half a quart and shouldn't hurt anything. As to checking it, you can connect a scanner and observe input rpm vs output rpm, calculated gear ratio, converter slippage, trans slippage, last shift time, shift time error, and good scanners can also check adaptive values as well as check for stored codes and any freeze frame data.

 

[stukreit]

I dropped the pan today. The fluid is 100,000 miles not-fresh but not abysmally stinky, burnt, or gritty. The bottom of the pan had no solid matter at all. The magnet had only the lightest coating of grey stuff, whatever it was, it was very fine and small quantity.

Pulled the TC cover down a bit. I could not remove due to other components blocking it.
There's no indication of leaks from any part of that area.

So I'd say we're in fine shape. I would still like to get operating temperatures and pressures during running. I do obd 2 codes with elm 327 wifi interface and iphone. Any clue of apps that pull transmission information?

 

[THEFERMANATOR]

I use a tech2 so I have no idea on apps to use. If your fluid drops with no visible leaks, check to make sure the transfer case isn't overfilled. The seals going into the transfer case fail and trans fluid runs back in and overfills it until it blows out the output seal and vent.

 

[JayTheCPA]

A couple of thoughts . . .

From general commentary, might consider doing another fluid and filter change in a few thousand miles. Reported reasoning is that the new fluid will clean-off stuff that had build over the last 100K miles. Also, folks whom change their fluid and filter around this point (and do not re-change them again shortly thereafter) tend to comment about a tranny rebuild not longer after a high-mileage fluid change. Supposedly, the second change along with the filter will get rid of all that freshly cleaned-off stuff and avoid the need for a rebuild. From experience, I fell into the rebuild crowd after a high mileage fluid / filter change, but my fluid was much worse than what you observed.


For holding the gear selection back in 2'nd or 3'rd while driving in town. Best bet is to get with a tuner for better TCC lock-up at lower speeds and lower gears rather than hold the slushbox back. Alternatively, consider an aftermarket transmission controller, but this is an expensive option. Yes, manually dropping the gears helps some, but from experience it is not all that much. GM pretty much designed the tranny in the GMT400 for pushing and not slowing as they left the TCC unlocked way too much. I offered a shift pattern to Slim that is a lot more stick-shift like than a slushbox and locks the TCC at much lower speeds starting with 2'nd gear, so might want to see if Leroy can get it for you.

 

[Will L.]

@stukreit not bustin on you, sharing opinion that hopefully some helps you and others.

My Hummer weighs in at a clean 10,000 lbs. A ton Over most, 2 ton Over others. Think pickup brakes are bad—Hummer brakes- sux. So many hummer owners downshift to save on the very frequent brake pads changes because they don’t know the shop is ripping them off telling them cut or replace the rotors every time.
Not unusual to see trans getting redone in 100,000 miles from it. SMH.

This leads to many of them learning 1 lesson:
Pay for brakes or pay for transmissions.

Luckily for me, I was familiar enough with the 4l80e to know it was designed to get you up to speed, not down from it. So I do it sparingly.

Btw, when a semi truck uses the engine as an engine brake, he flips a switch for the jakes to engage which disables some of the valves. Thos cyinders absorb undo and unequal wear to the others. Rigs where engine brakes are not used all the time get an in frame rebuild. When the jakes get rode hard- the inframe turns into everything comes out to go to the machine shop for vlave jobs and resleeve. Funny to me how all the new valve controlling in gassers (like 5.3,5.7 etc) screw up engines with shorter life and everyone acts surprised. LMFAO pinheads.

Not as many people as used to downshift transmissions for braking. ie: in hilled areas, brakes are used up and replaced much more frequently. But transmissions and engines last longer. This is why GM engineered it the way they did. If you are going to run your 6.5/4l80e or a 6.5/nv4500 like a big boy diesel- install he right parts like an exhaust brake, larger oil cooler with better oil filtering AND more frequently replaced oil to offset the cost. If manual trans, expect the higher heat into the flywheel. If auto, tell your builder what you are doing with it and crack open the wallet accordingly. And remember that pad and rotor wear is now inside your engine and transmission.

Or rip out the grocery getter brake system and upgrade it. They don’t build the brakes for daily mountain driving, or towing all the time. It is built for the masses. If your not running larger rotors, on ALL 4 corners with dual or quad pistons, and want to stop 15,000lbs comfortably or frequently... really? Why would anyone think brakes only twicw the size of a ford escort is going to do well stopping a truck weighing twice as much BEFORE the load is added and not have brake parts as a daily meal?

Remember back a couple decades when a pickup towing a large camp trailer used to be in the right lane getting passed going up AND downhill and it was normal? Now weekend warriors have to pass people while having a loaded toy hauler. Fine- but know that doing so cost $$$ to do it.

In the fleets I wrenched on with all the gmt400 trucks, most of them drive near empty- over half the time. “Loaded” meant500-1500 lbs. The ones that were towing frequently or loaded newr max all the time- unless it was under GM testing- first thing we did was upgrade braking. On the ones that stayed stock- new pads and a quick rolloc scuffing VERY frequently, with rotors getting outted for hot spots was the norm.
Imo, anyone that works a truck hard and has drum brakes is kidding themselves.

If you want the same device to accelerate your rig as decelerate it- you want an electric motor, not an internal combustion engine. Otherwise make the drive train drive it, and the brakes do the braking.

I’d say: enough said, but too much actually.

 

[stukreit]

I use a tech2 so I have no idea on apps to use. If your fluid drops with no visible leaks, che



ck to make sure the transfer case isn't overfilled. The seals going into the transfer case fail and trans fluid runs back in and overfills it until it blows out the output seal and vent.

Indeed, removed the top plug from transfer case and a good amount of fluid (1/2 to 1 cup)
came out. I have a 250 + 250 mile trip tomorrow. Assuming I keep checking transmission level every 200 miles, can I keep going until I can pull transfer case? If this is dicey, I can just
take another car, but it will less fun.

thanks,

Stuart

 

[WarWagon]

Quickest way to burn out the 4L80E's over run clutch pack is to compression brake with it. Guarantee to smoke it clean off is to do so with the TCC locked in. It's a small clutch pack with no room to beef it up.

Frankly if you want to compression brake get a different transmission. Otherwise the clutch pack burns up and you can't anyway.

You found a bad seal between the trans and transfer case. Fix it. Just drop the transfer case and the seal is on it. Otherwise you will keep loosing fluid into the tcase and low fluid burns up your trans.

 

[Jaryd]

In order to avoid a tow from 250 miles away if something was to happen would be worth driving something else in my opinion.

 

[FellowTraveler]

CarCode OBD2 will give all the info needed via its real time & data logging feature..............

 

[stukreit]

I have most of it apart and am doing some "while I'm in there" extras. Driveshafts and tcase
are out. Some of the u-joints are completely removed. Rear Diff yoke is coming off tomorrow due to leak. Maybe front diff yoke too.

Pro tip: unbolt cross member, lift tcase/trans, slide cross member forward to under trans,
stuff scrap wood under the trans pan to protect and take up slack, release jack, let
trans down on it.

1) Haven't dug into tcase adapter or trans tail piece to find the smoking gun of a leaky seal.
What should I expect to see? Some trans oil did leak out when the tcase started coming off the trans.

2) unconfident that u-joint part numbers are correct. I have 2 that came with internal circlips.
They appear to be the replacements for the front shaft which currently has the plastic
retainer. I got ACDelco 45U0108. I hope that checks out.
The rear driveshaft had external circlips are different dimension than the front and are different dimension than the front , so I can see I'll be buying 2 more.
Any help out there with a good parts diagram/parts number provider?

Again, this is a 1997 K2500 Suburban, 6.5td, VIN: ...VG521000

3) Rear Diff appears to have a plate or seal cover bolted on, which might be as leaky as the pinion seals. Again, need a good diagram/number provider.

4) Is Front Diff pinion seal replaceable the same way? The dealer's diagram showed a pinion
shaft that might have to be completely removed to get at it. Parts counter person was no help.

I will post pictures in the morning.

These are a lot of asks. Appreciation for any and all help.

Stuart

 

[stukreit]

Took it out for a test drive. At 45mph and up there is a new low pitch rumble. Perhaps the rear drive shaft got imbalanced or the u joints aren't perfectly centered? They appear to be fine. This drive shaft has a u joint at the diff, and another one at the sliding yoke at the tcase. no center bearing. The only imbalance thing I can guess is the sliding yoke is 180 off

Also the new tcase front output and the rear diff seals leak, so that's a re-do. I'll make a wood ring to help install the next ones more evenly and use a loctite sealer formulation that is speced for this application. But the u-joints, as I said, look like they're in place.

any suggestions re proving the driveshaft?

 

[smokymtn65]

Factory u-joints to my knowledge are installed with hot plastic then balanced , If it is out of balance after new u-joint so you will need to find a driveline shop that can re-balance it.. Someone correct me if I am wrong please.

 

[THEFERMANATOR]

Factory u-joints to my knowledge are installed with hot plastic then balanced , If it is out of balance after new u-joint so you will need to find a driveline shop that can re-balance it.. Someone correct me if I am wrong please.

This is only on half ton rear shafts with an auto. Sticks and trucks with 14 bolts did not have the nyloned ujoints.

 

[stukreit]

This is only on half ton rear shafts with an auto. Sticks and trucks with 14 bolts did not have the nyloned ujoints.

This 3/4 ton 14 bolt diff model indeed had nylon u joints on the FRONT driveshaft but the rear had outside clips. still looking for other references about this on the internet. no one seems to know about it

 

[smokymtn65]

Thanks for the additional info , it was 1/2 ton I was working on when I got told about it.

 

[THEFERMANATOR]

This 3/4 ton 14 bolt diff model indeed had nylon u joints on the FRONT driveshaft but the rear had outside clips. still looking for other references about this on the internet. no one seems to know about it

Thats why I said rear shafts, all front shafts with ifs are nyloned in.

 

[stukreit]

dunno if anyone is still following my foibles, but:

About 75 miles ago I replaced the transfer case front and rear output seals and rotated the rear shaft/yoke 180degrees.
The tcase is dry, the diff input seals are holding, and the rumble doesn't come on until 50+ mph. So, I will still be diy-balancing the driveshaft with 2 hose clamps but it should get much better now.

 

[stukreit]

Strange observation: there was no indication of leaking in the space between the transmission tail and the transfer case adapter.
I replaced the transmission output seal and tcase input seal anyway. The tcase was definitely overfull. Could the extra fluid get
there by way of the vent tube?