Strange hole in firewall. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Meatman · 11-07-2011, 12:00 AM

Only had my 68 for about two weeks now. Been going over her with a fine tooth comb. Discovered this today. PO had put tape over it on inside of cab. What is giant hole for? I cant figure it out.

**FirstOwner69** · 11-07-2011, 12:08 AM

Looks like the hole for a clutch rod. Automatic trans trucks used one of these at least to early 69 http://67-72chevytrucks.com/vboard/s...d.php?t=492610 Later trucks had a metal disk secured by screws top and bottom. The plastic plugs tended to "blow out" when the doors were slammed since they were attached from outside the cab.

Meatman · 11-07-2011, 12:17 AM

That was my one guess as to what it could be. I just didn't figure the hole would be there if truck was an auto originally.

vectorit · 11-07-2011, 12:28 AM

Clutch rod.

CTENTA1 · 11-07-2011, 12:49 AM

^^^what he said^^^

*stich626* · 11-07-2011, 01:07 AM

Quote:

Originally Posted by Meatman

That was my one guess as to what it could be. I just didn't figure the hole would be there if truck was an auto originally.

look for 2 screw holes at the bottom of the dash about 3 1/4 apart..
the old chapman cable lock..

OhioDan · 11-07-2011, 05:53 AM

Does this help?

Autoblueprint · 11-07-2011, 03:52 PM

Quote:

Originally Posted by Meatman

What is giant hole for?

There is a male/female four prong molded connector that fits this hole...it connects a 4 wire interior wire harness to the exterior wire harness for the turn signals, brake / running / reverse lights. I believe the wire harness colors are light green, dark green, yellow and dark brown if memory serves me correctly...it looks like you can see the exterior harness in the 2nd photo above and to the left of the hole.

**leddzepp** · 11-07-2011, 03:59 PM

Quote:

Originally Posted by Autoblueprint

There is a male/female four prong molded connector that fits this hole...it connects a 4 wire interior wire harness to the exterior wire harness for the turn signals, brake / running / reverse lights. I believe the wire harness colors are light green, dark green, yellow and dark brown if memory serves me correctly...it looks like you can see the exterior harness in the 2nd photo above and to the left of the hole.

That hole is further over towards the passenger side, and up higher. The hole in question is for the clutch rod, as stated above.

longhorn70gmc · 11-07-2011, 07:51 PM

This is a great question to ask. I go the same answers as to the pictures show and I discovered it on a 1968 LWB Chevrolet. I also found the rubber grommet that goes there as well still on the truck. Picture in your mind a Oval shaped like an egg and then it has a rubber sheath coming off of it about 2 to 3 inches long. This is what the linkage was routed through. I view the hole as godsend, so I don't have to make anymore in my fire wall. I am currently using it for my Vacuum gage line and when I finish the TAC it will also go through this whole. The grommet is hard to find because I admit I have been trying everywhere including the internet, but removed the old grommet from that 1968 and have refurbished it with High Temp Black RTV to make it fresh again until I find a nice new one. I am going to go find some kind of packing to fill it when I am done to keep the rodents out of the cab. I just redid my seats. Good Thread and am glad you asked.
R/
Billy

cleszkie · 11-07-2011, 09:22 PM

That is the rarely optioned spark plug inspection port.

Meatman · 11-07-2011, 11:55 PM

Thanks for help guys. Now I just need to find a plug for it.

longhorn70gmc · 11-08-2011, 02:44 PM

Quote:

Originally Posted by cleszkie

That is the rarely optioned spark plug inspection port.

I enjoy the humor on this because this was such a search in trying to figure this out; thanks for the good laugh!!!!!!
R/
Billy

longhorn70gmc · 11-08-2011, 02:48 PM

Quote:

Originally Posted by Meatman

Thanks for help guys. Now I just need to find a plug for it.

For now I am reusing the original grommet I found. There has been a cotton rag stuffed in it for the past 19 years. It was always hidden under the firewall insulation on the inside of the cab like in your picture, but I noticed it from time to time from the engine bay. Can't explane why I never bothered to investigate. I have that it has to be fixed now syndrome and never did anything on it till now. Good Luck on your search. I would love to see a follow up picture of what you end op doing.
R/
Billy

11-07-2011, 12:00 AM	#1
Meatman Registered User Join Date: Sep 2004 Location: Topeka, Ks Posts: 604	Strange hole in firewall. Only had my 68 for about two weeks now. Been going over her with a fine tooth comb. Discovered this today. PO had put tape over it on inside of cab. What is giant hole for? I cant figure it out. __________________ Daily-94 K2500 350 5spd extended cab longbox Project Red Velvet-68 C20 396-th400-AC-PS-PB-all original except for the 8 track and the gun rack. Build thread>>>>http://67-72chevytrucks.com/vboard/s...d.php?t=495881 My 01 TA and 88 Formula hide in the garage. :-)

11-07-2011, 12:08 AM	#2
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,842	Re: Strange hole in firewall. Looks like the hole for a clutch rod. Automatic trans trucks used one of these at least to early 69 http://67-72chevytrucks.com/vboard/s...d.php?t=492610 Later trucks had a metal disk secured by screws top and bottom. The plastic plugs tended to "blow out" when the doors were slammed since they were attached from outside the cab.

11-07-2011, 12:17 AM	#3
Meatman Registered User Join Date: Sep 2004 Location: Topeka, Ks Posts: 604	Re: Strange hole in firewall. That was my one guess as to what it could be. I just didn't figure the hole would be there if truck was an auto originally. __________________ Daily-94 K2500 350 5spd extended cab longbox Project Red Velvet-68 C20 396-th400-AC-PS-PB-all original except for the 8 track and the gun rack. Build thread>>>>http://67-72chevytrucks.com/vboard/s...d.php?t=495881 My 01 TA and 88 Formula hide in the garage. :-) Last edited by Meatman; 11-07-2011 at 12:40 AM.

11-07-2011, 12:28 AM	#4
vectorit What? Join Date: Jun 2007 Location: Southern California Posts: 7,617	Re: Strange hole in firewall. Clutch rod. __________________ Chris 1968 K20 Suburban 1972 K10 LWB PU

11-07-2011, 12:49 AM	#5
CTENTA1 Registered 1971 K5 Join Date: Dec 2008 Location: SO.CEN.CAL Posts: 428	Re: Strange hole in firewall. ^^^what he said^^^

11-07-2011, 05:53 AM	#7
OhioDan Registered User Join Date: Apr 2002 Location: New Carlisle, Ohio,USA Posts: 1,404	Re: Strange hole in firewall. Does this help? Attached Images __________________ LIFE AIN'T EASY WHEN YER FAT AND GREASY! GMC= Got More Class! 1970 GMC LWB, Fleetside, 350/4spd, Flowmaster "40's", 2002 GMC 16" Rallies, cowl hood,and added a bunch of options that weren't there when I started.

11-07-2011, 07:51 PM	#10
longhorn70gmc Senior Member Join Date: Feb 2001 Location: Ridgecrest. CA, USA Posts: 1,715	Re: Strange hole in firewall. This is a great question to ask. I go the same answers as to the pictures show and I discovered it on a 1968 LWB Chevrolet. I also found the rubber grommet that goes there as well still on the truck. Picture in your mind a Oval shaped like an egg and then it has a rubber sheath coming off of it about 2 to 3 inches long. This is what the linkage was routed through. I view the hole as godsend, so I don't have to make anymore in my fire wall. I am currently using it for my Vacuum gage line and when I finish the TAC it will also go through this whole. The grommet is hard to find because I admit I have been trying everywhere including the internet, but removed the old grommet from that 1968 and have refurbished it with High Temp Black RTV to make it fresh again until I find a nice new one. I am going to go find some kind of packing to fill it when I am done to keep the rodents out of the cab. I just redid my seats. Good Thread and am glad you asked. R/ Billy __________________ Billy 1970 GMC Sierra Grande 402/TH400 (Longhorn)14 years and counting rebuild! 1975 (Build) Chevrolet SWB 4X4 350 SB Lifted 6 inches 1970 Ford F250 Ranger 390 BB 2010 Ford Super Duty F250 XLT W/4 inch lift kit and Pro Comp Tires Hub Cap Freak! *I need another truck like I need another hole in the head!* I'M IN THE MARKET...AS IT WERE!

11-07-2011, 09:22 PM	#11
cleszkie Registered User Join Date: Feb 2003 Location: Santa Ana, CA Posts: 2,191	Re: Strange hole in firewall. That is the rarely optioned spark plug inspection port.

11-07-2011, 11:55 PM	#12
Meatman Registered User Join Date: Sep 2004 Location: Topeka, Ks Posts: 604	Re: Strange hole in firewall. Thanks for help guys. Now I just need to find a plug for it. __________________ Daily-94 K2500 350 5spd extended cab longbox Project Red Velvet-68 C20 396-th400-AC-PS-PB-all original except for the 8 track and the gun rack. Build thread>>>>http://67-72chevytrucks.com/vboard/s...d.php?t=495881 My 01 TA and 88 Formula hide in the garage. :-)



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