Transmission drain plug on THM700R4 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

oborowsk · 07-29-2014, 01:10 PM

Hi,
86 Chevy C10 and 305 engine is being rebuilt as I write this. Took transmission off (THM700R4). Since draining transmission fluid was a pita, want to install aftermarket drain plug. What is the best location for that? Has anyone done this? I plan on brazing the plug in so no future issues with leaking etc. Is best place on the bottom? On the side of the pan? Since transmission is out, I don't know if I randomly chose a place to put it, it might interfere with some brackets, etc. when I bolt it back on the engine. If someone could take a picture of what it looks like under the truck without everything taken off, that would also help. Took it off some time ago and don't remember what it looked like. In the future, I will take pictures of everything before I disassemble things. Done this for the engine compartment, but nothing else. Live and learn.....

Thanks

GRADYS Performance · 07-29-2014, 02:55 PM

Why not put a cast Aluminum pan with a drain plug already in it to replace the stock pan? If you put a drain in the stock pan put the drain so that all the fluid will drain out by putting the plug flush with the pan bottom.

S10Fan · 07-29-2014, 07:04 PM

I welded mine in a flat corner area. Welded a bung on the outside of the pan for zero chance of any interference. If you're unable to locate a bung locally, just use a 1/2-20 jam nut as a bung, and the same size drain plug.

**hatzie** · 07-29-2014, 09:54 PM

You can get a steel pan from Spectra, CFR, Dorman, or Summit with the bung and drain plug already installed.
The downside is they are thinner than the stock pan weighing in at 4-6 lbs. I believe the stock pan is prolly around 10-15lbs.

07-29-2014, 01:10 PM	#1
oborowsk Registered User Join Date: May 2014 Location: Rocklin, California Posts: 12	Transmission drain plug on THM700R4 Hi, 86 Chevy C10 and 305 engine is being rebuilt as I write this. Took transmission off (THM700R4). Since draining transmission fluid was a pita, want to install aftermarket drain plug. What is the best location for that? Has anyone done this? I plan on brazing the plug in so no future issues with leaking etc. Is best place on the bottom? On the side of the pan? Since transmission is out, I don't know if I randomly chose a place to put it, it might interfere with some brackets, etc. when I bolt it back on the engine. If someone could take a picture of what it looks like under the truck without everything taken off, that would also help. Took it off some time ago and don't remember what it looked like. In the future, I will take pictures of everything before I disassemble things. Done this for the engine compartment, but nothing else. Live and learn..... Thanks

07-29-2014, 02:55 PM	#2
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: Transmission drain plug on THM700R4 Why not put a cast Aluminum pan with a drain plug already in it to replace the stock pan? If you put a drain in the stock pan put the drain so that all the fluid will drain out by putting the plug flush with the pan bottom.

07-29-2014, 07:04 PM	#3
S10Fan Old Heap Driver Join Date: Mar 2008 Location: Newport News, Va Posts: 2,640	Re: Transmission drain plug on THM700R4 I welded mine in a flat corner area. Welded a bung on the outside of the pan for zero chance of any interference. If you're unable to locate a bung locally, just use a 1/2-20 jam nut as a bung, and the same size drain plug. __________________ _____________________________ Bryan '99 Silverado 1500, 4.3, 5-speed, reg cab, short bed '50 Chevy 2DR Hard Top, 350/350, M2 Front End, 3:08 gear, cruiser. '40 F**d Sedan, all Chevy power, Heidt's front end, TCI rear, nice driver.

07-29-2014, 09:54 PM	#4
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,932	Re: Transmission drain plug on THM700R4 You can get a steel pan from Spectra, CFR, Dorman, or Summit with the bung and drain plug already installed. The downside is they are thinner than the stock pan weighing in at 4-6 lbs. I believe the stock pan is prolly around 10-15lbs. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.



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