Issues with my 06 GXP

[rguy200073]

Bought the car with 100,010 miles on it at the end of August. Car literally is in mint. I had to look at the carfax to believe that it had the mileage listed on the dash. I received all of the repair history with the car from oil changes to the transmission replacement at 62k and 66k. I never would have bought a car with this kind of mileage on it if it wasnt for the documentation.

I immediately noticed that there was an exhaust leak on the drivers side but didnt really care for I wanted to put a new exhaust on it anyways, and it stood out being that it is of course a V8.

Also have been really paying attention to the tranny for I had a 60 warranty from the delership on the powertrain. I have driven aggressive using the TAP shift and it has done pretty well...especially in normal drive.

Other than the battery change, the car is really solid. However....

What i have noticed about the car is that it felt as though the tranny shifts hard, and would "slip", along with the tranny reaching over 230 degrees at times. I figured that since the warranty was up in just a few days, i should have them look at the car and tell me what they find.

Turns out that it had 2 broken engine mounts! That may explain why it gave me the impression of the tranny slipping or shifting rough. It was the damn engine moving! I am not sure though if the tranny has issues or not. It only has 40k on it now but if the stock went out at 62k, it may only be a matter of time before I have to replace and/or upgrade.

So the shop bill came to over $700 that was covered under the 60 day warranty and they fixed the exhaust leak for free. The car feels like a brand new car with new engine mounts. Feels more solid and seems to accelerate faster and more smoothly. The downside is that with the exhaust leak being fixed, i find it hard to tell if the car is running. These damn cars are so quiet!


Anyways, the point is...with the mileage over 100k, what items could I be replacing in the near future? I know every car is different, but what are the common items to look out for? Are these engines good for 150k+?


Thanks for your time and help everyone!

[Scottydoggs]

put a external cooler in for the trans, it will help keep the trans at a cooler temp. heat kills a trans.

[rguy200073]

put a external cooler in for the trans, it will help keep the trans at a cooler temp. heat kills a trans.

Yeah this seems to be the first thing to do.....thanks!

[Fivefingerdeathpunch]

Spark plugs, if they never have been done.

Otherwise really you are just waiting for normal wear parts like pulleys and ti rods/wheel bearings and so on to start going.

[rguy200073]

Spark plugs, if they never have been done.

Otherwise really you are just waiting for normal wear parts like pulleys and ti rods/wheel bearings and so on to start going.

Good to know. I know the 3.8s are bullet proof and just did not know how these 5.3s hold up. Figured being part truck motor and part LS1, they should be pretty reliable.

[colindunn]

the transmissions in the gxp's wear faster because of heat and constant hp/tq strain. make sure you use full synthetic oil. DOD uses the oil system to operate and if the engine sludges up enough bad things can happen. Otherwise they are great engines. If it isn't burning oil.

[rguy200073]

the transmissions in the gxp's wear faster because of heat and constant hp/tq strain. make sure you use full synthetic oil. DOD uses the oil system to operate and if the engine sludges up enough bad things can happen. Otherwise they are great engines. If it isn't burning oil.

Yeah no oil burning here. Runs really strong too! I mean...for a 5.3. It already has gone through one tranny...the replacement was new and hopefully was a better tranny than the stock one.

[rguy200073]

Quick question....when they replaced this tranny with a new replacement one at 60k+ miles, knowing that there was an issue, would it be safe to say that it was replaced with a OEM tranny under the extended warranty, or an upgraded tranny that addressed the stock tranny issues? I just dont know if there was a fix for the issues these things have.

[Scottydoggs]

if they told you they put in a new GM tranny, then you now have a new trans, the warranty will only last as long as your cars warranty last. after that, your on your own.

[rguy200073]

if they told you they put in a new GM tranny, then you now have a new trans, the warranty will only last as long as your cars warranty last. after that, your on your own.

The repair history I got (off of the extented warranty) showed everything that was done to it over the course of the last 5 years. The tranny was replaced twice within the 60k-70k mileage range. Dont know why 2 times, but it was probably replaced with a brand new OEM then? I guess I was just hoping for an updated OEM that corrected the main issues.

[Swiggles]

The fwd trans sux, plain and simple. You should be saving for another especially if you continue to beat on it like you were. Not much can be done about it unfortunately, you should get the trans cooler if your seeing temps over 180.

The fwd Cadillacs used the same trans I believe.

[Fivefingerdeathpunch]

There arent really any "upgrades" to the new designed 4T65e HD that came out in 03-04 from the factory.

The upgrades are left to the trans shops that build these for our cars. Be it clutches, chains, input shafts etc etc. The new OEM trans you got would be the same trans that came in it off the line. Likely it sat on a shelf in a warehouse and was shipped there and installed.

The fwd Cadillacs used the same trans I believe.

IIRC they used the 4T80e and even the newer 6 speed auto in the cadillacs come 08. But both the v8 bonnie gxp and that buick v8 still used the 4 speed.

[Swiggles]

i thought the gxp got the 4t80e? maybe that was the bonnie gxp and the the gp gxp upgrade is the 4t80e?

[Fivefingerdeathpunch]

Grand Prix GXP is still the 4T65e with 2.93 gearing.

Bonnie GXP is the 4.6 northstar with the 4T80e.

[Swiggles]

Oh ok, what another brilliant move from gm lol.

[91parkave]

Oh ok, what another brilliant move from gm lol.

the 4t80 would be awesome but leaves little to no room for exhaust modifications i.e headers and such. If only we could snatch that beefy chain and make it work in the 65-e on the cheap

[Koniig]

Water pumps are pretty notorious for going out on the 5.3 as well.

[colindunn]

Water pumps are pretty notorious for going out on the 5.3 as well.

No, that was your fault. jk.



the 4t80 doesn't even bolt up in a grand prix. with modification it does tho. it would be easier to just build a 4t65

[rguy200073]

the 4t80 doesn't even bolt up in a grand prix. with modification it does tho. it would be easier to just build a 4t65

So what are the most common upgrades to the 4t65?

[Fivefingerdeathpunch]

New clutches, upgraded input shaft, stronger chain, shift kits.

If you browse Triple Edge Perfomance's webiste it can give you an idea of all that can be done.