I gang! I am new to this forum and hope to get some answers!

I run my own Corvette site, but, uh, the Suburban is just a touch different. We have a 1999 LT, long version, with 8 person seating, dual AC, leather... black with tan interior, all the power stuff. 350 V8, 4L60E, about 118k miles.

I have a few questions....

1. The damned gas gauge... it moves about much like bowl of jello in an earth quake... full, empty, half, empty, full, quarter... you get the idea. Thoughts? I am thinking the gauge.

2. Fan... the fan that drives the AC for the dash vents. It seems pretty weak. I am wondering if a duct door is blocked or what not. Is this a common problem?

3. A clunk... in the left rear door, sounds like something is really loose in there, but I have'nt pull the door apart to check. Is there anything in the doors that does normally come loose over time?

4. What is the life span of the 4L60 (or is that a 4L65E)?

5. The brakes are super mushy, I have been told this is normal. Is there a fix?

That's about it! Thanks for having me!

 

ok. The gas gauge. The baffles in the tank could be bad, or, if the gauge is hooked right up to the sender then there could be a bad capacitor as they sometimes use capacitors to smooth out the signal

The weak ac fan. You need a new speed resistor. They can get worn out.

The transmission. SERVICE IT! If you havent yet, change the filter and give a FULL fluid flush. Then change the filter every 30~40k or so and it should stay in good shape.

 

Thanks for the reply, Joe!

I doubt it's the baffles... it happens just sitting there... stopped... with the engine idling... most odd.

The fan is blowing hard, I can hear it, but it's just not making it to the dash. Like the ducting is either blocked or redirected somewhere. I know the resistor you speak of, and normally, it will fail all you get is high speed, because the resistor is more like a potentiometer and is slowing down the fan, keeping it from running at full speed.

I will do the trans service! GM spec fill ok? Or is synthetic better? Mobil 1 vs Amsoil vs Valvoline? I am not immune to getting the best fill available. If spending $50 saves me $1500, I am all for it. I assume the flush process is the same regardless, either pay someone with a power flush, or, remove the upper coolant hose and get a bucket and start pushing fluid out. It's not elegant, but it sure does work.

 

year and mileage? if it has 1 check the cabin air filter and if im understanding right the gas gauge bounces around just sitting still with the key on? I've replaced a lot of clusters for that but its worth testing not just throwing parts at

 

Oh joy. Well, I believe Gm has a monkey ho randomly picks which cars have the cabin air filter. As Some Chevy do, some don't. My 2007 Burb doesn't. But sounds like your Burb does.

I Used what advanced had cause it was on sale. Castrol Full synthetic Dex VI. I bought 18 quarts. When I was done, bye bye old factory, Hello bright red new synthetic.

 

Cleveland - it's a 1999 with 118k miles.

Cabin air filter? Hm... I will check the owners manual for that. That would make a lot of sense... fan running strong, no air coming out. Sure does fit the symptoms, like to the T. Considering this truck started in TX and is now in SoCal (original owner moved, according to CARFAX), it went from the #1 dust capital in America to the #2 dust capital in America...

I will get the fluid this week, along with the filter kit.

I will confirm that the gauge bounces with just the key on vs engine running. It does it with a full tank, half tank... That's why I think it's the gauge and not the tank. It could also be a bad sender.

 

if you dont have a cabin air filter then you ac coil is blocked and you will have disassemble the HVAC box to clean the AC coil and heater core. If its been through a lot of dust I would rinse out the radiator and condenser for better performance.

 

good points, both, Joe. Thanks!

I am going to check that out in a bit.

Updates later!

 

99 should have a cabin filter on the passenger side under the glovebox, just remove the 2 screws on the sound dampener and you can push it out of the way enough to access the filter door. 7mm for the screws on the dampener and i think its a 5mm for the screw holding the cabin filter door on, theres 2 rectangle filters make sure you check them both.

if i remember right the trucks/suvs stopped using cabin filters in 02 the cars seem to depend on how lazy the assembly shop was that day

 

So far, what I have learned, is that 1999 1500 series Suburbans have them, 2500 series do NOT, but the pick-ups, DO. Whew.

I have new filters (WIX) on order at my local O'Riely's... I know I could cheaper, but they are quick enough and my wife's health demands good working AC, especially as we get into fire season.

And yes, I noticed that the kit includes 2 filters, that explains a lot.

I saw a video on cabin filter replacement, and I can easily see how it would get all clogged up... wow, what a mess if bugs and other debris. I will need a vacuum to clean it out!! According to the video, it was a 7mm (9/32) and a 7/32 (which sounds pretty close to 5mm).

Thanks again!