T Top Question - Need Help Please

[Kurt B.]

I am trying to order replacement weatherstripping for my 68 T tops and when describing what I have on there now, the vendor suggested I may have the late 70s t tops and therefore require a different product than I was ordering. The existing weatherstripping goes all the way around the top and in the area where the side door glass meets the t top, I have an additional weatherstrip that is approx. 18 inches long and is metal reinforced and has a groove to receive the window glass. I purchased the car in 1972 and never changed the tops or weatherstrip so how is it possible that I have late 70s tops or weatherstrip?
I want to order the correct part but this late 70s weatherstrip didn't exist when I bought the car so what do I have on there and what should I buy?
Any help appreciated and as soon as possible please as I ripped the old off last night and need to reorder.
Thank you,
Kurt # 26406

[Reba Whittington]

Re: T Top Question - Need Help Please

You most likely have original or pre-1972 service replacement, as the original weatherstrip had a metal reinforcement window channel, while reproduction that I have seen does not. (Maybe Joe Lucia will help here.)

1968-69 top weatherstrip was different from the later 1970-76 style, and I am not sure it if it is available from any manufacturer. The 1970-76 style will work with some modification of the push-in fasteners.

There was a design change in 1977 or 78, and the later style T-top will not work on a 1968, so you can't have the entire later top.

Also do you mean that that your weatherstrip is two pieces? If so, that is incorrect. All top w/s came as one piece.

[Kurt B.]

Re: T Top Question - Need Help Please

Reba,
Thank you for your response. My existing wetherstrip is one piece but at the door glass it has the heavier piece with metal reinforcement and it is riveted in place at the leading corner with one rivet. Everywhere else, it is held on with adhesive and the push in plastic pins.
Are you saying that what is on my car is a service replacement?
Also, should I NOT order the later style with the metal reinforcement?
Thank you,
Kurt

[Jim T.]

Re: T Top Question - Need Help Please

Kurt it would seems reasonable to me that the t-top w/s that is on your t-tops is the original w/s since you have owned your 68 since 72. Given your area of the US, your car probably was not exposed to severe hot temps sitting in the sun.

[Joe L.]

Re: T Top Question - Need Help Please

Kurt-----

When it comes to C3s I'm a "convertible-kind-of-guy", so my expertise regarding t-tops coupes is lacking. But, I'll provide some information regarding what I do know.

1968-69 Corvette coupes used t-top weatherstrip which was different than later years. As a matter of fact, it was of a 2 piece design. A "horseshoe-shaped" piece fit around the front, inside and rear sides. A straight piece connected the ends of the horseshoe on the outside, door window side. The part numbers for the "horseshoe" piece were GM #3935521, LH, and GM #3935522, RH. The straight pieces were GM #3935527, LH, and GM #3935528, RH. For late 1969, or, perhaps, for SERVICE only, the horseshoe shaped pieces became GM #3965151, LH, and GM #3965152, RH. All of these weatherstips are long-since GM discontinued and, as far as I know, not reproduced.

Starting with 1970 models a 1 piece weatherstrip was utilized. This weatherstrip was originally known as GM #3966571, LH, and GM #3966572, RH. Later, about 1974, the part numbers were changed to GM #362953, LH, and GM #362954, RH. At the moment, I do not know exactly how these 2 sets differ, but I believe that the original set was used in PRODUCTION for 1970 through about 1973 and the second set was used in PRODUCTION from about 1974 through early 1977. Later, the second set became the SERVICE replacements for the earlier. These are the weatherstrips with 19 push-in fastners and are the ones that can be used to SERVICE 1968-69 models, although they were never catalogued or specified by GM for 68-69 SERVICE.

For later 1977 through 1982 the weatherstrips used were also a 1 piece design of GM #362985, LH, and GM #362986, RH. I believe these are the weatherstrips with 18 push-in fastners. These weatherstrips are NOT adaptable to 68-69 or 70-early 77 Corvette applications.

[Reba Whittington]

Re: T Top Question - Need Help Please

Thanks, Joe, always learning. I guess I had never seen any truly original 1968-69s with the two-piece--only the SR.

Kurt, be sure and claify "later" with the vendor. As Joe said, a 1977-82 style will not fit your car. Ask about reproduction for 1968-69 with metal reinforcement. If it is available, that is what you need for originality. But reproduction 1968-76 without the metal will work. We have installed it on many cars. Good luck, l968s are such fun to buy for, aren't they?

[Kurt B.]

Re: T Top Question - Need Help Please

Thanks to all for your input.
Joe, you hit it on the head and the 2 piece w/s you described is exactly what I have. Boy, now am I ever sorry I took it off, it wasn't in bad shape. Just thought that since I replaced everything else on the car, I might as well replace this also. Big mistake. Nothing but pieces now. Sometimes I am my own biggest enemy.

Interestingly enough, the straight piece that meets the window glass is "adjustable" because the 4 screws that hold it down, screw into tiny movable plates that can move 1/8 inch in and out so one can tailor the fit.
Kurt 26406

[Kurt B.]

Re: T Top Question - Need Help Please

Joe,
I have to contradict you. Your expertise is not lacking. I just spent the last hour cleaning up the piece I removed and right there big as life is the GM part # 3935528RH. You were right on the money as usual. For a convertible guy, you sure know your coupes. The piece is in very good condition, almost excellent actually. I wonder if I can fabricate my own 2 piece set up by buying the repro one pice w/s and cutting it and reusing my straight piece. Your thoughts on this?
Also, you oftern use the terms "Production" and "Service" when refering to parts. Can you elaborate on these terms and how parts with each designation would differ. I'm trying to learn.
Thank you,
Kurt

[Joe L.]

Re: T Top Question - Need Help Please

Kurt-----

I'm not really in a position to comment one way or the other regarding your idea on converting the later style weatherstrip by cutting out a section and using the original straight section. A lot depends upon the end configuration of the original "horseshoe" shaped piece. Given that you have the straight section pieces in good condition, I would certainly recommend trying your idea out. I have a "gut" feel that it would work. But, my lack of familiarity with the actual pieces leaves me at a disadvantage to comment further.

Regarding the terms PRODUCTION and SERVICE, a PRODUCTION part is the particular part used for any specific application on the assembly line. A SERVICE part is a part sold through GM Service Parts Operations in order to replace a part used in PRODUCTION. Most often, PRODUCTION and SERVICE parts are the same. However, sometimes parts, even of the same part number, change over time due to revisions to the blueprints for the part or due to alternate manufacturing specs which the original drawings allow for. Different suppliers may manufacture a part over time and avail themselves of alternate manufacturing specs which are specified.

Original parts are sometimes superceded in SERVICE. When this happens, a later model PRODUCTION part may be used used to SERVICE an earlier model. Very often, this is because a part is improved in later model PRODUCTION and the benefit of that improved part is extended to SERVICE parts for earlier models. This benefits both the consumer and GM; the consumer gets the benefit of the improved part and GM has to stock less parts in its service parts system. Of course, restorers might not see it this way, but the VAST majority of GM's parts customers are more concerned with getting the benefit of an improved part if it can be used on their car and FAR LESS concerned with maintaining exact original configuration.

Sometimes, when original parts used in PRODUCTION and SERVICE are discontinued, GM will substitute a "one-size-fits-all" type part. In these cases, the SERVICE part is totally unlike not only the original PRODUCTION part, but unlike ANY PRODUCTION part. These are SERVICE-only parts. They are usually significantly inferior to PRODUCTION and original SERVICE parts. However, they will SERVICE the application and most customers are primarily interested in obtaining a part that will repair their car. Usually, when the "one-size-fits-all" SERVICE parts come into play the car is somewhat old and, likely, nearing the end of its service life. Owners are glad just to be able to get a part that will repair their malfunction and are not otherwise too picky.

Rarely, there exist situations where the original parts used in PRODUCTION are never available in SERVICE. In these instances, SERVICE-only parts may be available to allow for repair or replacement of original parts. Many fastners fall into this category; the parts used in PRODUCTION are never available through GMSPO channels. One has to make do with available "standard parts".

Many times, the parts used in PRODUCTION are assemblies which are not available in SERVICE. In SERVICE, only the individual components of the assemblies are available. In these cases, the PRODUCTION assemblies are never sold through GMSPO. Through GMSPO one can only purchase the individual parts used to make up the PRODUCTION assembly. However, once the individual parts are assembled, one has the exact same thing as the PRODUCTION assembly. This sort of thing is done when individual componets can be field-assembled AND when some significant parts of the PRODUCTION assemblies are usually re-usable in SERVICE.

[Kurt B.]

Re: T Top Question - Need Help Please

Joe,
Thank you for a very informative and detail explanation. This is exactly what I was looking for. Now I know a little bit more than I did before I asked, and that's the goal of learning, right?
Have a good weekend.
Kurt