While the Chevrolet Turboglide was ultimately a dead end, it was an essential step in automatic transmission development at General Motors.
The first generation of automatic transmission development at General Motors followed two distinct tracks. First was the four-speed planetary gearbox as embodied in the 1940 Hydra-Matic. Next came the torque-converter based transmissions, namely the Buick Dynaflow and the Chevrolet Powerglide. Chevy’s next automatic transmission, the Turboglide introduced in 1957, was also a torque-converter transmission, but with some important advances and enhancements over the Powerglide.
For starters, the Turboglide was the first GM automatic to use an integrated, diecast aluminum case. (But it wasn’t the first in the industry, an honor that goes to the Packard Ultramatic.) The aluminum case (top photo) greatly reduced weight and also eliminated many potential sources for leaks, and it soon became the standard practice in the Motor City. Beyond that, the Turboglide was much like the Powerglide in basic layout, with a torque converter in front and a pair of planetary gearsets that provided two forward gear ratios and a reverse.
The Turboglide’s major internal departure was in the torque converter, above. While the original Powerglide used a simple three-element coupling, the Turboglide used a five-element converter with a dual-angle stator and three successive turbine stages with decreasing torque multiplication ratios, one overrunning the next. (In this regard, the Turboglide was more like a Dynaflow than a Powerglide.) The effect is not unlike a continuously variable transmission of the current day, with engine rpm held in a relatively narrow range when the the vehicle is accelerating—although the mechanism is completely different.
While the three-stage turbine provided the torque multiplication, there was a driver-selectable low range, mainly to provide engine braking on downhill grades. On the column shift selector, this feature was labeled HR for Hill Retarder. But unfortunately, some owners assumed the HR meant High Range so Chevrolet changed the labeling to GR for Grade Retarder.
Continually updated and treated to a major revision in 1959, Turboglide was offered on Chevrolets and Canadian Pontiacs through the 1961 model year as an extra-cost option in the $50 neighborhood. While the transmission was more troublesome and expensive to repair, it seems the limiting factor in its popularity was that most Chevrolet owners were satisfied with the cruder-shifting but perfectly functional Powerglide. For 1962 the Turboglide was discontinued, replaced by a redesigned Powerglide that borrowed some of the Turboglide’s advanced features.
Back in the late 1960’s I was a line mechanic at a Chevy Olds dealer. A 1960 Chevy came in with a rusted transmission cooler line which was an EZ fix. I test drove it and immediately thought the trans had sustained some damage, as it wouldn’t shift. An older mechanic then told me it was a Turbo Glide and wasn’t supposed to.
Turboglides were notorious for reverse range failures. If you parked “headed-in” to a barrier and transmission “R” range failed, you were SOL. Had that happen to me with my new 1960 Impala four door hardtop parked against a parking lot log in Zion National Park.
After keeping the engine revved up, enough pressure built up in the transmission that the car backed away enough that I was able to shift into drive and be on my way. Local dealer checked it out and, I think, added fluid because I don’t remember having the problem again.
When I was in tech school (1974), our transmission teacher had a fair amount of experience with the Turboglide. He told us many of the units died because some drivers (mostly teenagers) liked to put the shifter in the HR/GR position and race around, thinking they were in low gear. Of course the stator was in its reverse pitch mode & in essence the engine was fighting the transmission, causing the transmission temperature to skyrocket! You can guess the outcome.
Don Sutherland’s reply is spot-on. I had two 61 TGs and never had any problem. I knew what they were and didn’t drive ’em like a PG using L. GR was ONLY for increased downhill braking. People who didn’t know how they worked messed them up by driving them like GR was L. It wasn’t.
Turboglide’s new design of a one-piece case which bolted directly to the block required a new location to mount the starter motor. Powerglide had used an adapter which mounted the starter motor; manual transmission the clutch housing.
Thus was born a starter design which became nearly a a GM standard for 50+ years. Namely a pad-mount starter motor which used vertically oriented bolts to anchor the starter to a pad cast and machined into the block. Eventually all GM divisions used this design for almost all applications.
However, to start with only Turboglide mated engines utilized the pad-mount starter. Despite the limited application, apparently ALL engines had the pad cast, machined, and holes threaded for the Turboglide-only starter. A “hidden” cost of offering Turboglide?
Beginning with aluminum Powerglide in ’63 more and more applications began to utilize the pad-mount starter.