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       Is your 4-speed transmission getting hard to shift?  Does it grind whenever you shift gears?  maybe it will pop out of gear when you decelerate.  Have you been hearing a low whirring sound or even a growl?  Well, Bunkie, it is time to rebuild that trusty Super T-10 4-speed transmission.  All of these noises are a sign that something isn’t right inside of that transmission.  Hard shifting, popping out of gear and grinding are symptoms of worn or chipped synchronizing rings.  The whirring or growling sound could be worn bearings.  These problems can all be corrected with one call to Zip Products, Inc., 8067 Fast Lane, Mechanicsville, VA 23111, (800) 962-9632,  They have a complete 4-Speed Rebuilding Kit available that includes all of the needle and roller bearings, synchronizing rings, washers, shims and snap rings needed.  Please keep in mind that rebuilding a transmission is not for everyone.  You will need specialized tools, a hydraulic press, and an understanding of how a 4-speed transmission operates and is assembled.  You will also need more than average mechanical ability.  But even if you cannot do the work yourself, this article will give you a much better understanding how a 4-speed transmission works and a better understanding as to what is involved with a total rebuild.  For those of you with an older Borg Warner or Muncie 4-speed transmission, most of these procedures done here are the same so this article will also be of help to you.  If you are ready, let’s get started.

   Zip Products has a complete selection of replacement gears, cluster assemblies, bearings, synchro assemblies, shafts and seals to complete your transmission rebuild.  Visit Zip-Products.com for your specific needs
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01: This is the complete Rebuilding Kit that we received from Zip Products.  It includes all of the needle and roller bearings, seals, gaskets, shaft, snap rings, washers and O-rings that you will need for a normal rebuild.  You will also need a hydraulic press, bearing pullers, seal pullers and more than common hand tools.  A shop manual and a unit repair manual for your year Corvette is a must.
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02: Remove the transmission from your car as per your shop manual’s instructions.  Thoroughly clean the exterior.  After the transmission is clean you can look for the transmission code and VIN numbers stamped into the case.  If the last 6 digits of your VIN number match the last 6 digits stamped on the transmission case, you have the original transmission for your Corvette.
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03: Drain the transmission then remove the 9 bolts that hold the side cover in place. Carefully remove the cover and shifting forks.
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04: Mark the shifting forks with their corresponding clutch assemblies. Also make sure you mark which end of the fork was at the top of the clutch assembly. These forks wear with the clutch assembly as they move back and forth so you want them to stay with their respective clutch assemblies. Note: For reference, 1st gear is at the rear of the main case. 4th is at the front.
Click to Enlarge 05: With the side cover removed, spin the shaft slowly and look at each gear and synchro ring. You will look for chips in the gears, pits or worn brass synchro rings. If you look closely in this picture you can see how worn this synchro ring’s teeth have become. They have lost their sharp edges and became rounded.

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Click to Enlarge 06: Remove the retaining bolt and clip and pull the speedometer gear out of the tailshaft of the transmission.
Click to Enlarge 07: With the speedometer gear removed check for any worn, broken, cracked, chipped or flattened teeth. If you find any, replace the gear.
Click to Enlarge 08: Drive out the lock pin from the reverse shifter boss.  (Look carefully at the end of the pin.  You will see that one end is thicker than the other and can only be removed in one direction.  Drive the pin out from the bottom of the boss to the top.)
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09: Pull the shifter shaft out partially to disengage the fork from the reverse gear.  Remove the 5 bolts that attach the tailshaft to the transmission main case.  Use a soft blow hammer to tap the tailshaft rearward until the reverse idler shaft is clear of the reverse idler gears.  Now rotate the tailshaft to the left.  Turn the reverse shifter shaft to free the fork from the gear and remove the tailshaft.  Clean off any of the old gasket.
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10: Remove the speedometer gear outer snap ring and then tap or slide the gear off the shaft.  The second snap ring can now be removed.  Here you can see the snap rings and gear are removed from their position on the shaft.
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11: Here is the reverse gear.  The area of the gear that is being pointed to has been worn through use.  This is the grinding noise you hear sometimes when you put the car in reverse.  This type of wear is fairly common and will not hurt.  If the wear was more severe, then the gear should be replaced.
Click to Enlarge 12: Use a soft blow hammer to tap the reverse gear off the shaft.  Then remove the rear portion of the reverse idler gear from the transmission case.

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Click to Enlarge 13: Remove the 4 input shaft collar retaining bolts and gasket from the front of the transmission.  You may need a soft blow hammer to tap it loose.
Click to Enlarge 14: Now remove the front bearing snap rings and washers.
Click to Enlarge 15: Use a bearing puller and collar to remove the front main drive gear bearing.
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16: Shift the 1st and 2nd, 3rd and 4th clutch sliding sleeves forward.  This will allow adequate clearance for the mainshaft removal.
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17: Next remove the rear retainer lock bolt and slide the mainshaft and rear bearing retainer out of the case.  The front reverse idler gear and thrust washer can now be removed from the case.