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Does anyone on the planet have ANY, repeat, ANY information, pictures or knowledge of the Hi-torque rearends which were installed in the 1956 Corvettes that were modified to race at Sebring in Mar of 1956?
I have searched around forever trying to find some information on these super, ultra rare rearends and have never been able to find anything about them. The best information I have come up with is that they had HT either cast or stamped on them.
Anyone here have ANY knowledge?
Tom- Is it possible that that posi was simply a modification of the existing unit ? in the late 60s/early 70s we modified the posi cases with special made bearing caps to make them a little stronger. Because of limited use/demand of the HT unit you mention, a new unit was not made, but rather modified from the existing units and therefore no special casting # or stamped number.
Tom- Is it possible that that posi was simply a modification of the existing unit ? in the late 60s/early 70s we modified the posi cases with special made bearing caps to make them a little stronger. Because of limited use/demand of the HT unit you mention, a new unit was not made, but rather modified from the existing units and therefore no special casting # or stamped number.
I DO NOT know.
That's why I'm asking. For many years I've chased this phantom with ZERO results. The ONLY thing that has been determined is that some (and there were only 4) of the 56 Sebring race cars had SOME KIND, repeat, SOME KIND of posi rear and it was callet a Hi-torque. Information and /or pictures of what type of case, what type of guts, etc, etc, have never surfaced (to my knowledge) and I've inquired with multiple people/sources--------------------and NOTHING has come to light! Thus, I cannot answer ANY questions, because I've never been able to obtain any information or pictures of the 56 Hi-torque rears. Nor have I ever seen any information on a quantity. SOMEBODY ON THIS PLANET HAS TO KNOW SOMETHING ABOUT THEM!!!!!!!!!!!!
I DO NOT know.
That's why I'm asking. For many years I've chased this phantom with ZERO results. The ONLY thing that has been determined is that some (and there were only 4) of the 56 Sebring race cars had SOME KIND, repeat, SOME KIND of posi rear and it was callet a Hi-torque. Information and /or pictures of what type of case, what type of guts, etc, etc, have never surfaced (to my knowledge) and I've inquired with multiple people/sources--------------------and NOTHING has come to light! Thus, I cannot answer ANY questions, because I've never been able to obtain any information or pictures of the 56 Hi-torque rears. Nor have I ever seen any information on a quantity. SOMEBODY ON THIS PLANET HAS TO KNOW SOMETHING ABOUT THEM!!!!!!!!!!!!
Just sent your email 1956 tech service bulting on 1956 positraction. They designed it in the summer of 1956. DANA built the first prototype. I do not believe any 56 Corvegtte had the post rear end as it was not approved by SCCA until 1957 . NASSAU race December 6-8, 1956 had the new 57 fuel injection motors...and positraction.
As I recall, the "Hi-Tork" diffs were made in Detroit by a guy named Rich Lyeth (pronounced "Leeth"); he built the one in my B/Msp Nailhead-powered '53.
As I recall, the "Hi-Tork" diffs were made in Detroit by a guy named Rich Lyeth (pronounced "Leeth"); he built the one in my B/Msp Nailhead-powered '53.
John,
Tell me what you can or what you know about the Lyeth rears.
John is correct. I think I have a copy of one of the Work Orders. If you have a supply of mid-'50s Hot Rods & Motor Trends, look for the advertisers under the spelling "High Torq". I'll try and get into the binders tonight, but it may take a while......
Tom, not quite what you were looking for, but I found the order for the spare "High Tork" for Sebring. Order from Lyeth Engineering, 12859 East Eight Mile Road, East Detroit MI for six assemblies, 3 3.55s and 3 3.70s, Lyeth part # 61-17-00. Also order from Gear and Axle 3 sets of 3.55 (#3725830 & 3725831) and 3 sets of 3.70 (3725864 & 3725865) gears.
After purchase, deliver to Mr. Ray in the "Axle Room" to have gear sets "lubrited", rework differential carriers by adding a sheet metal baffle above the Hypoid Gear, send 3.70s to Florida and retain the 3.55s for "future disposition". It would appear that the carriers were stock "reworked" units.
By the way, they cost $70 each.
I'll look for an earlier order tonight or tomorrow.
Last edited by desertpilgrim; Oct 17, 2017 at 10:52 AM.
There's an article titled More '56 Race Program Information in the Spring 2014 NCRS Restorer written by Dick Robinson. There's a letter there from Chevrolet Engineering to Dana Corp to design a Powr-lok differential. Is that the same thing ?
Last edited by John BX NY; Oct 17, 2017 at 11:58 AM.
There's an article titled More '56 Race Program Information in the Spring 2014 NCRS Restorer written by Dick Robinson. There's a letter there from Chevrolet Engineering to Dana Corp to design a Powr-lok differential. Is that the same thing ?
John,
ANY information or pictures that appeared AFTER Mar 1956 would (presumably) have eventually led to the resultant Positraction, manufactured by and supplied to GM, by DANA. That Positraction became a Chevrolet regular production option in late Dec of 1956. In the fall of 1956 there was only ONE differential case, casting number 3725899. And that case was a NON-posi case which was used for several following years. Then, in Dec 56, there was a second case for Positraction, casting number 3743833. This was the FIRST (to the best of my knowledge) usage of these two differential cases in EITHER pass cars or Corvettes.
The differential case that was used in ALLLLLLLLLLL 56 cars and Vettes was 3707306, and this was a TOTALLY different casting
number for 56 only. Thus, where I'm going with this, is that if a VERY SMALL quantity of Hi-tork positraction units were built for installation into a 56 differential case, then that case almost assuredly had to be ONLY a 306 casting. Right? Wrong? What?
I have ZERO clue how many of you out there have been rebuilding these early rears, but I've been building them for people for over 50yrs. During this time, I've picked up a few things, and the one single thing I've never been able to run across is a genuine 1956 Positrack/Hi-tork rear--------------------and so far, no one seems to have any solid, honest to God, information or pictures of a real Hi-tork posi BEFORE, repeat, BEFORE Mar 1956.
This is a 56 (306 casting) case. Notice the outlined areas of this case compared to the same outlined areas on the next case, which is the 57-later style. As can be seen the second case has thicker, stronger areas to support the side carrier bearings.
This is inside a 57-later case that was used for NON-POSI rears. Notice the triangular shaped gusset which is in ALL Non-posi cases beginning in 1957-------------------THE 56 CASES (306) DID NOT HAVE THIS GUSSET!
This is inside a 57-later style posi case---------------NOTICE, NO GUSSET! This is why (beginning Dec 56) there were two different cases cast, one for non-posi (gusset), one for posi (no gusset), because the gusset was in the way of the larger posi unit.
As a side note, to modify a non-posi case for installation of a posi unit, the gusset of a non-posi case is simply cut out (which I have done to many cases for posi conversion).
Besides some mentions in letters about "Hy-Tork" (sic), the January 1956 instruction bought Lyeth's #61-17-00; directed an oil baffle over the Hypoid gear; oil baffles in each housing leg similar to HD Service Axle Housing #3731296; designed an Axle Housing Vent and located it above the oil baffle on top of the banjo; axle shafts same as 3714781-2 except that flanges and portions outboard is the same as Halibrand #H828; axle shafts and bearings to conform to Halibrand and to make another assembly at ratio 3.27.
Remarks indicate that Elco #28 Rear Axle Lubricant will be the only lube issued for these axle assemblies; Hy-Tork will not work with Lead Soap Active Sulfur Lubricant.
John,
Tell me what you can or what you know about the Lyeth rears.
Tom, I planned on beating the bejeezus out of that rear end with the 6-71-blown "nailhead" in my '53, and Joey Lishin (owner of the Motor City Speed Shop) hooked me up with Rich Lyeth to build the rear end. Joey also built my 6-71 blower drive setup - very talented guy.
[QUOTE=John BX NY;1595781687]There's an article titled More '56 Race Program Information in the Spring 2014 NCRS Restorer written by Dick Robinson. There's a letter there from Chevrolet Engineering to Dana Corp to design a Powr-lok differential. Is that the same thing ?
For those of you who are familiar with these early rears, with posi, then you may know that there are now two aftermarket posi units for these early rears (56-62 Vette/55-64 pass cars): Eaton and Nitro Power Loc.
The Eaton is like the typical 10bolt Eaton posi unit they have had for many years (one piece unit), and the Nitro unit is a 2-piece unit which is nearly identical to the original DANA supplied posi units, but with some welcome improvements. Both are good posi units. I've converted several NON-posi rears using both and have not seen any issues with either.
Below is an Eaton posi unit compared to an original DANA posi unit.
This a Nitro unit, and a partial disassembly showing the inside.
1956, YES, 1956 Hi-Torque "positrack"
