T-10C rebuild - bad/interesting news

[Rob Edwards]

I had dropped off the boss's '62-340 at Corvette Mike's on Monday for them to look at the tranny and shift linkage, as she was slipping out of third gear, getting stuck in two gears at once, and the shifter was buzzing like a beehive at speed. (That enough symptoms for ya?) In any case, I got a call today, they've got her apart and said that third gear is bad and needs to be replaced, fair enough. They also said that the main tranny case and tailshaft housing BOTH needed to be replaced. The tailshaft housing has a fracture thru one of the shifter mounting bosses that would be 'expensive' to fix properly, while the main tranny case is apparently no good because, if I understood correctly,one of the recesses in the case itself is so worn that the number of shims required to hold whatever (layshaft? total guess on my part) goes in it would be a temporary and ill-advised fix. I have the entire powertrain photgraphed and have all the P/N's so I'll be sure that I get all the original (correct!) pieces back.
So- She's coming back with a new shift lever assembly, tranny case, and extension housing. From this admittedly confused report, can anyone tell me what was wrong with this tranny? The car did have racing stripes on it at one point, FWIW. I don't know what replacement case they're using, but given that it's going to be mounted to an RPO 396 motor, are they limited to some particular species of T-10, or will any cast-iron Chevy passenger T-10 work? They quoted $85 for a replacement case, so I'm guessing it's the latter. Any opinions here? (Other than I'm a dummy for not being there when it came apart and seeing the damage firsthand, and that it's clear I don't know much about transmission rebuilding!) Thanks!

[Mike M.]

Re: T-10C rebuild - bad/interesting news

if you all are installing a mark 4 396 in a 62 vette, not do away with the t-10 and put a muncie, richmond 5 speed of a ZF-6 in the old girl? mike

[Rob Edwards]

Re: T-10C rebuild - bad/interesting news

Mike-

Sorry, I meant the original 340hp 327 (RPO 396), not a 396ci motor. My bad.

[Joe L.]

Re: T-10C rebuild - bad/interesting news

Rob------

I think that they have likely properly diagnosed the transmission's problems. All of the items that they identified as deficiencies are fairly common on T-10's, especially those subjected to abuse over the years. However, I don't agree with their "fix" for all the items:

1) the 3rd gear replacement is fairly simple; if it needs a third gear, simply replace it with another. I'd recommend using a NEW gear, though. These are available in reproduction for T-10s. Considering that fact, I would stay away from a used gear. Who knows how much life is left in it or how much abuse/wear that it's already sustained? I'm not saying that they installed a used gear, but I'd check with them on this;

2) If the extension housing is cracked, a replacement is probably the way to go. New, correct parts are generally not available for this item. However, a good used one, properly reconditioned with new bushing, should be fine. To have the CORRECT part for a 62 T-10 you'll need an extension housing with a T-10-7D casting number;

3) If the existing main case is original to the car (i.e. the car's VIN derivative is stamped upon it), then I would definitely try to re-use it. The sort of damage that they described to you can be repaired by a T-10 expert like Larry Fischer or Ed Hartnett. Preserving the main case, IF ORIGINAL, is worth what it costs and it really wouldn't cost all that much. Likely, it wouldn't cost much more than a replacement, used case. If the main case in the car is NOT original, then replacement with another good used original-type case is the way to go. For an original-type case, you need an ALUMINUM case with a T-10-1C casting number.

In any event, make sure that you get the USED parts that they removed from the transmission, especially the main case and extension housing. Under California law they have to give you the replaced parts unless the parts are sold "exchange". In the latter case, pay the "exchange" charge and take the parts, ESPECIALLY if the case was original to the car. You definitely don't want to leave an original case behind.

[Rob Edwards]

Re: T-10C rebuild - bad/interesting news

Joe-

Thanks for your $0.02 - I will ABSOLUTELY get back the original main case and extension housing. I also specifically asked for all the guts that come out of the T-10, no matter how trashed, as I figure I'll learn something from the mess. I may not have accurately recounted what exactly they were trying to tell me was wrong with the main case, so we'll see what they say; I'll ask them again and post their reply. I will find out their 3rd gear source and what sort of main case they're planning on using and go from there.

-Rob