Automatic Transmission Oil Pans

[Joe L.]

I was reminded again today of the dumb thing that GM has done since time-immemorial: no drain plugs on automatic transmission oil pans. As has always been the case, this makes changing transmission fluid and filter a REALLY messy job. This is especially true since for most auto transmissions, there is a lot more fluid in the transmission than is contained by the oil pan. A drain plug would make this job so much easier.

[Patrick H.]

Re: Automatic Transmission Oil Pans

Joe,

There's one on my 2003 GMC truck, but when I went to change the fluid the bolt was so stuck I had to drop the pan anyway.
So, even when I finally had a drain plug on a GM vehicle it didn't help.

Patrick

[Terry M.]

Re: Automatic Transmission Oil Pans

Joe,

There's one on my 2003 GMC truck, but when I went to change the fluid the bolt was so stuck I had to drop the pan anyway.
So, even when I finally had a drain plug on a GM vehicle it didn't help.

Patrick

Patrick,
Those truck pans are deeper than the standard pan (at least for TH400 & 4L60). There were, and maybe still are, issues with that bolt on PRODUCTION and SERVICE deep pans. I had to have one drilled out also, but another yielded to a really good impact wrench cranked all the way up. It was remarkable to try to hold the impact on the bolt at full blast and have nothing happen.

Edit Add:
Dave Perry informs me that the deep (truck) pan and drain plug will work for the 4L60e, but there is no available "long reach" filter for the 4L60. So i suspect while the deeper pan will fit on the 4L60 transmission one only gains the added fluid capacity and risks the filter being exposed above the oil which is not a good thing. I also neglected to mention that when adding the deeper pan(s) one should get the long reach filter as well. The benifit of the deeper pan is not only the drain plug, but the added fluid capacity. On the other hand the deeper pan on my Caprices, Patricks truck and Dave's SyTy trucks are not a ground clearance issue (at least not with standard suspension), a Corvette would be problematic in that regard.

And here this started out about adding/removing drain plugs and look where it got me?

[Jim T.]

Re: Automatic Transmission Oil Pans

My 1970 Corvette is an original owner and was used as a daily driver for many years. Having the turbo 400 and knowing I would be changing the transmission fluid in future use I installed a drain plug in the transmission pan before NCRS was formed to not make such a mess when it was time to change the fluid and filter. Have accumulated over 160,000 miles with several transmission fluid and filter changes on original turbo 400. Installed a magnet inside the pan also. Another change was changing to a thicker gauge turbo 400 GM pan. The pan change stopped fluid from leaking around the perimeter of the pan gasket.

[Patrick H.]

Re: Automatic Transmission Oil Pans

Patrick,
Those truck pans are deeper than the standard pan (at least for TH400 & 4L60). There were, and maybe still are, issues with that bolt on PRODUCTION and SERVICE deep pans. I had to have one drilled out also, but another yielded to a really good impact wrench cranked all the way up. It was remarkable to try to hold the impact on the bolt at full blast and have nothing happen.

Edit Add:
Dave Perry informs me that the deep (truck) pan and drain plug will work for the 4L60e, but there is no available "long reach" filter for the 4L60. So i suspect while the deeper pan will fit on the 4L60 transmission one only gains the added fluid capacity and risks the filter being exposed above the oil which is not a good thing. I also neglected to mention that when adding the deeper pan(s) one should get the long reach filter as well. The benifit of the deeper pan is not only the drain plug, but the added fluid capacity. On the other hand the deeper pan on my Caprices, Patricks truck and Dave's SyTy trucks are not a ground clearance issue (at least not with standard suspension), a Corvette would be problematic in that regard.

And here this started out about adding/removing drain plugs and look where it got me?

An additional problem on my truck - the pan has a bracket on the driver's side that holds the cable for the shifter. The bolts that hold this in place are on the top, and after Michigan winters plus dissimilar metals (steel bolts, aluminum trans) the bracket bolts can't be removed. So the pan can drop down only a tiny bit on the driver's side, barely giving enough room to install a new pan gasket. So, preventive maintenance can sometimes be a lot more work than you'd expect.

[Edward J.]

Re: Automatic Transmission Oil Pans

An additional problem on my truck - the pan has a bracket on the driver's side that holds the cable for the shifter. The bolts that hold this in place are on the top, and after Michigan winters plus dissimilar metals (steel bolts, aluminum trans) the bracket bolts can't be removed. So the pan can drop down only a tiny bit on the driver's side, barely giving enough room to install a new pan gasket. So, preventive maintenance can sometimes be a lot more work than you'd expect.

Pat, been there many times with the transmission drain plug removal on gm trucks, it seems they must use a sealer or Loctite on the plug along with a shallow head bolt most certainly will round of the head almost every time when trying to remove. If you really want to change out the fluid in the transmissions today, a fluid exchanger is the only way to go. and wait until you change out a C5/C6 automatic, No fill tubes or dip sticks there, pump it in from below.

[Joe L.]

Re: Automatic Transmission Oil Pans

Pat, been there many times with the transmission drain plug removal on gm trucks, it seems they must use a sealer or Loctite on the plug along with a shallow head bolt most certainly will round of the head almost every time when trying to remove. If you really want to change out the fluid in the transmissions today, a fluid exchanger is the only way to go. and wait until you change out a C5/C6 automatic, No fill tubes or dip sticks there, pump it in from below.

Edward-------


Generally, when one replaces the fluid, one should also replace the filter. So, this necessitates the removal of the pan.

[Edward J.]

Re: Automatic Transmission Oil Pans

Joe its a good practice I have pulled many transmission pans down for services over the years, but todays cars you may think twice as removal is next to impossible on some vehicles, You would be amazed at the some of the cars and trucks today and exhaust system pipe routing, cross members and here in the Northeast salt and corrosion is a big issue, It seems no one changes transmission fluid until 100k plus or maybe never. so you see what I am up against. and Ford New World transmissions don't even have a interval for service. I will pull the dip sticks on cars and trucks to look at the fluid condition, If its not black I would not even touch, If it still has somewhat of a red color I will do a fluid exchange, Black means its to late to doing anything will only put you up against a wall if the transmission fails after you service. vintage corvettes and cars are easy so that's a no issue I agree. I am only stating what pertains to newer cars and trucks. I rarely see filters dirty today It seems as though if the transmissions have made it past the warranty periods and they don't have problems they will make a 100/200k.

[Joe L.]

Re: Automatic Transmission Oil Pans

Joe its a good practice I have pulled many transmission pans down for services over the years, but todays cars you may think twice as removal is next to impossible on some vehicles, You would be amazed at the some of the cars and trucks today and exhaust system pipe routing, cross members and here in the Northeast salt and corrosion is a big issue, It seems no one changes transmission fluid until 100k plus or maybe never. so you see what I am up against. and Ford New World transmissions don't even have a interval for service. I will pull the dip sticks on cars and trucks to look at the fluid condition, If its not black I would not even touch, If it still has somewhat of a red color I will do a fluid exchange, Black means its to late to doing anything will only put you up against a wall if the transmission fails after you service. vintage corvettes and cars are easy so that's a no issue I agree. I am only stating what pertains to newer cars and trucks. I rarely see filters dirty today It seems as though if the transmissions have made it past the warranty periods and they don't have problems they will make a 100/200k.

Edward------


I can understand that; I believe that modern engines and transmissions as well as chassis "packaging" of same are designed with the "wing and a prayer" that they'll never need to be serviced. If they do, good luck!

By the way, does a "fluid exchange" remove and replace ALL the fluid in the transmission (including that held in the torque converter)?

[Keith B.]

Re: Automatic Transmission Oil Pans







this looks to good to be added

[Joe L.]

Re: Automatic Transmission Oil Pans

this looks to good to be added

Keith------


There's absolutely no doubt that this drain is original to this pan. However, is this an OEM oil pan or aftermarket? Many aftermarket pans have a drain.

[Keith B.]

Re: Automatic Transmission Oil Pans

Joe the first picture is the stamp of the pan. That matchs to the car it belongs too witch is a 67 427/390 built in June of 67

[Edward J.]

Re: Automatic Transmission Oil Pans

Edward------I can understand that; I believe that modern engines and transmissions as well as chassis "packaging" of same are designed with the "wing and a prayer" that they'll never need to be serviced. If they do, good luck!By the way, does a "fluid exchange" remove and replace ALL the fluid in the transmission (including that held in the torque converter)?

Joe yes the machine pumps out about 95+ percent and inc.s torque convertor, it is measured and new fluid is pumped back in.

[Ray G.]

Re: Automatic Transmission Oil Pans

An additional problem on my truck - the pan has a bracket on the driver's side that holds the cable for the shifter. The bolts that hold this in place are on the top, and after Michigan winters plus dissimilar metals (steel bolts, aluminum trans) the bracket bolts can't be removed. So the pan can drop down only a tiny bit on the driver's side, barely giving enough room to install a new pan gasket. So, preventive maintenance can sometimes be a lot more work than you'd expect.

Patrick;
The bracket you write about can be bent enough to allow the pan to clear and be removed. The slight amount of lateral adjustment will not affect shift points.
Also the transmission drain plugs can be removed by using a sharp chisel and catching the outside diameter in a "lefty loosey" rotation. Sometimes you will need several attempts to loosen the drain plug. Being careful not to touch the trans. pan.
Reinstall with antisieze compound.
Have seen several mechanics make a hex on the outer diameter. The original 15 MM size to small for this size plug.
We always change filter and screens when dropping the pans.
On tow vehicles we change whatever fluid can be drained with Dexron VI, with every engine oil change.
Hope this helps.

[Patrick H.]

Re: Automatic Transmission Oil Pans

Patrick;
The bracket you write about can be bent enough to allow the pan to clear and be removed. The slight amount of lateral adjustment will not affect shift points.
Also the transmission drain plugs can be removed by using a sharp chisel and catching the outside diameter in a "lefty loosey" rotation. Sometimes you will need several attempts to loosen the drain plug. Being careful not to touch the trans. pan.
Reinstall with antisieze compound.
Have seen several mechanics make a hex on the outer diameter. The original 15 MM size to small for this size plug.
We always change filter and screens when dropping the pans.
On tow vehicles we change whatever fluid can be drained with Dexron VI, with every engine oil change.
Hope this helps.

Ray, thanks for the tips. I changed fluid at 100,000 miles, and it has 152,000 now. Based on the body rot (rockers, rear quarters) due to the heavy salt use on west Michigan's roads I don't think that the truck will make it to 200,000 for the next fluid and filter change. I'll let the next owner or the junkyard worry about what to do with it next.