ok, Ill try this one more time. I need to find a grommet for a 78 L48 auto no cruise. I have ordered from two different vendors and neither are correct, in fact, I cant even find a hole that they fit into anywhere on the firewall. It looks like just about all of the vendors show something different on their websites. Surely someone here has purchased this grommet and can point me to the right one. The one that came out looks something like the battery cable grommet. No guarantee that its the right one since bubba has definatley hit this car (probably will again before im done with it ). For reference, the hole that I "believe" it is supposed to go through is to the left of the brake booster facing the transmission.

 

Hi,
What passes through the grommet?
Regards,
Alan

 

I used a pvc valve grommet for a hole that I had wires running through might wanna see if it will work.

 

oops..I guess thats a key piece of information

Speedometer cable.

 

Is it #4, because you make me look now I need one to!

A PCV grommet sounds like an easy fix.

 

Hey pete, thanks but im really not so sure. At least on my car, those two holes are NOT the same size. So there is no way they could use the same part number as the FSM indicates. Like I said, I have ordered what was supposed to be a sppedo grommet for a 78, auto, no cruise...two vendors, two different grommets, neither fits either hole.

 

The original p/n 3824713 was replaced by 332650. Our notes in our computer system (which goes back to 1980) shows this grommet was replaced in June of 1975.

And while this is odd, it does happen from time to time... But the production line number stayed the same all the way up to 1982 production even though the GMPD number was 332650. You'll find in the 1981 parts book the only number listed in 09.975 group for a speedo cable grommet is this number (332650) showing 1970-1982 application. Both are now discontinued... but think I have some NOS left, I'd have to check. Our current part number is EC18

Both grommets were the same with a round hole, a metal reinforcement inside and three retaining tabs. Try putting one on... They are next to impossible to get over top of the cable especially on the cars with the screw on speedo heads (1968)

The grommet was also used on a/c cars where the line passed through the core support.

One of the main issues... When people replaced the cable they usually tossed this grommet with the cable and if you ever tried to put one on you'd know why. Most people thought this cable grommet was made on the cable since they are so hard to get off and on. The other issue is when you sell one, the customers are looking for a normal style grommet and not anything that looks like this. The grommet doesn't fit in the hole per say, it is just held against the firewall by the three folded over fingers.

If you received a grommet that looks like the one below, I'm afraid you have the correct grommet and the arduous task of trying to install it.




Added Note.. 332650 was replaced by part number 474579 and I don't have this date noted. But the new number, 474579 was just a soft rubber grommet that was in no way correct and did not have any means of fastening itself to the firewall. You would have to glue this one on if you tired to use it.

 

Willcox, thank you for the information, you guys have been extremely helpful on this forum. I do have a grommet that looks something like that one. The problem isnt getting the cable over it, its that the grommet doesnt actually fit the hole. The hole to the left of the brake booster is too big, the one to the right seems too small, but the bigger problem there is that the grommet rubs up against the firewall and cannot actually get it centered over the hole.

 

Okay.. here is my update.

I have a 77 and a 76 car here that are being dismantled. The two cars have the same grommet as I pictured above and have pictured below to document its accuracy.

Now I have a 1978, and 1979 but both cars were missing the cable and grommet.



But....

We are working on a 1980 today w/o cruise control car in the shop. It doesn't appear to be modified but it does appear as if it has the soft grommet 474579. <--- THIS IS WRONG!! Today I looked at this closer... the softness was from the grommet coming part. The grommet on this car is just as pictured above.

Willcox

 

Thank you so much! Can you do one additional favor? In those pics above, can you back out a little so I can see where you are on the firewall? Mine was completely out of the car when I got it, I have the AIM but I just want to be sure we are looking at the same holes here. I probably will not get to it much this weekend anyway (I need to replace the exterior lights on my C5 and put another coat of POR15 on the floorboards of the 78).

 

I've solved this I think.. few minutes plz

 

I'm still working on this.. .but my statement above changed.

The 1980 does have the original grommet in it and it is the 332650 style grommet. The appearance that it was soft was because the grommet is falling apart.

Wondering if your car didn't have cruise at one time. The hole B seems to be for cruise only cars and varied in size from the different cars I checked today. One was 1.5 another was 1.25. Below this hole is a standoff platform that changes the angle to where it is perpendicular with the car. It appears that this where the hole is located for MT cars. C in my picture.

Hole A seems to be for cruise control cars possibly and for all AT w/o Cruise cars.

 

OK, so here is what im working with. A and B measure just as you show...1" and a little over 1.5 respectively. I have a pronged grommet, and it does fit into A, except that it is so close to the kickout area for the brake booster that it will not fit in all the way and does not seal on that side.



Here are the different grommets I have. The large one is what was in B...that had a manual choke cable through it...no idea what was supposed to go there. The center one has no prongs on the back (474579?). The other one is what you indicate as the correct grommet. What gets me is that the diagram fro the AIM would indicate that hole "B" would be correct for my car and requires the larger grommet.

 

are you wanting a grommet for where the cruise wiring would go, but a grommet with no hole for the cruise wiring??? That grommet does not have the tabs( I think).. It has the slot on the edge to fit the fire wall into?

 

I just want to find out what hole the speedometer cable needs to go through and what grommet will work there. It would be nice to know what is supposed to go through the other opening as well.

I suppose its possible that the car was a cruise car at one point, its a salvage title. But then I would imagine I would see the switch on the dash...although i'm not really sure what I'm looking for there. Right now my plan is to use "B" as I "think" I have a grommet on the way that will work there. I can use A to run some other wiring for my electric headlight motor conversion.

 

Automatic no cruise would have used the hole right next to the brake booster, or in my drawing A. The hole should be no larger than 1" and if it is, someone has messed with it. I can find no example in all the old firewalls we have here where this hole is larger than 1".

The car did have cruise before. The large grommet should fit in your hole B. This would be the grommet from the cruise control harness and to my knowledge that hole would not be there if it were not a cruise control car... all you would feel there is a dimple. Both examples I have here do not have that hold drilled... both do not have cruise.

MT cars would have had another hole for the cable and it too would have been 1" in diameter drilled where my picture indicates hole C.

Both the grommets you have a correct, the one in the middle is the replacement GM version and soft... it's p/n 454579. The one on the right is the correct original grommet and again, it was part number 332650

 

I think someone has enlarged your hole A... my opinion...

 

No, hole A is 1", Just as you depict. It is just too close to the kickout for it to seal well against the firewall.

Notice the aim, base model shows it through hole "B". This depicts a single cable (no cruise) going into the trans on the pass side (correct for the auto trans). I'm beginning to think that this is actually correct and the larger grommet is the correct one. Im just curious as to why no one lists that part as a speedo cable grommet. I found one through doc rebuild listed as simply "firewall grommet".

So let me ask you this...you car obviously has the same hole open (B)...if not the speedo cable, then what goes there?

 

I keep saying "In My Picture" because the hole B in my picture is different than the one referenced in the AIM. Hole B in my picture was only there if the car had cruise control.. it used the huge grommet you have on the left in your picture.

Your cable should go though hole A and I don't see any reason why it won't go in there, it's no different than the hole I just pulled the cable out of in my first picture.

The "other" hole... C was drilled in the standoff located below my hole be.. You can see it in the picture above too.. where the cable on the 80 (with mt) is going in the side.. No other firewall I have here has that hole.

Look at the first picture I posted on the left hand side.. you can see where the grommet didn't seal all the way up by the darker shade to the fiberglass.

Willcox

 

interesting, I must be seriously confused. So the AIM is just wrong here? Cruise should have a two piece cable, correct? How else would I be able to tell if this had cruise at some point. I know I can use hole B with the grommet I have (I have a new version of the large one in my picture), but now its become a matter of principle. If this car had cruise...why remove it? Or better yet...if what you say is true...why is the AIM just wrong?