Do I have a shallow or deep tranny pan

[lmholmes11]

I plan on changing my internal transmission filter while I already have the tranny drained to change the fluid. Do I have a shallow or deep pan? 2001 Chevy Duramax, crew cab.

Does anyone have any helpful tips while changing the fluid?

[DmaxMaverick]

It should be a shallow pan. No GM light trucks were originally equipped with the Allison deep pan. It's aftermarket.

Why change the internal filter? Allison recommends only changing it at overhaul. You shouldn't need to change it.

[lmholmes11]

Well I figured I should since my truck has 130K miles and I'm the second owner, so I'm not so sure it has ever been done before.what all is included with an overhaul?

[DmaxMaverick]

Overhaul is overhaul: A complete teardown and replacement of all wear parts (frictions, steels, valves, gaskets, packings, seals, etc.....) and damaged parts. It's unlikely yours has been overhauled (check the service history by VIN at the dealer). Still, no reason to drop the pan, unless it'll help you sleep better. Wasted effort and expense, IMO. The internal filter is essentially little more than a clod sifter, while the external spin-on filter does the fine work (change that one often).

[lmholmes11]

Thanks for the reccomendation Dmax, how many miles is recommended on a tranny for overhaul?

[DmaxMaverick]

Immediately following your need for a tow truck.

The tranny is stout, and should go a long way if you don't abuse it. 300K+ is common. I've never heard of one failing under normal use. I know of a couple that quit early on, but there was something obviously wrong with them. It's still a mechanical device built by human hands. If you haven't had any issues before 130K miles, it'll probably hang in there for the duration. Just keep up the regular service and watch the fluid condition. Always schedule a service immediately following a severe incident, if the fluid spends any time above 240°, and soon if above 220° for an extended period. Heat kills the fluid, and will eventually kill the tranny if left unchecked. I use and recommend 100% synthetic ATF (Amsoil, but others are good).

[lmholmes11]

Ok thanks for the input and reassurance. If I do decide to drop the pan to check things out, do you reccomend putting locktite or some other kind of thread protector on the bolts when I reinstall?

[DmaxMaverick]

No need for a thread locker as long as it's installed and torqued properly. The gasket is reusable unless damaged, and the bolts/threads should be dry (use brake cleaner). Oil or any other substance can effect the torque values and damage the gasket and pan. (due to excessive/inconsistent tightening).

[THEFERMANATOR]

Yep, make sure and torque the pan bolts down evenly and slowly as the actual acts to strengthen the trans case. And the internal filter is more or less just a metal screen that prevents large pieces of material from going into the trans, the spin on filter does all of the actual filtering. Just make sure that the magnet is present in the spin on as many are discarded through the years when the filter gets changed.

[lmholmes11]

Ok thanks for the help guys. While chainging fluid, should I flush, or just drain old fluid and replace with new?

[DmaxMaverick]

If it has a lot of miles and it's never been flushed, I suggest you do. If you are replacing dino fluid with synthetic, you should (to take full advantage of the synthetic). It's easy and doesn't take much time. You will need more fluid, though. About 20 qts.

Don't forget to replace the spin-on filter AFTER the service, and reinstall the magnet on the filter.