Interesting, could you please provide a source for this? I was under the impression that the Panther was always unreliable as the designers cut corners when it came to the gearbox and final drive which hindered it strategic reliability wise for its entire operational service. When you referred to reliability, did you mean the strategic reliability, or tactical reliability?
It improved, but it never got good. Take, for example, the French impressions of the Panther from their post-war use of it. I'm also going to paste in a post of mine from a previous Panther thread, because quoting stuff with quotes in it is hard to read:
Reliability was a problem with all Panthers from the day they were deployed at Kursk -only 15% of them managed to get to the battle, and throughout the war:
Germany's Panther Tank by Thomas Jentz
Panther-Abteilungen in the West
On 28 June 1944, Guderian reported on experiences in opposing the Allied landing in Normandy: The Pz.Kpfw.IV, V, and VI have proven to be successful. The Panther appears to catch fire quickly. The lifespan of the Panther's motors (1400 to 1500 km) is significantly higher than the Panther's final drives. A solution to the final drive problem is urgently needed. The fasteners for the Schuerzen must be strengthened to prevent them from being torn off by the hedgerows in the Normandy. Soon the troops will demand that protective armor shields be mounted over the rear decks because of the success of fighter-bomber attacks. The height of the guns in the Strumgeshuetz is too low for the terrain in Normandy.
The general consensus of the industry was that inner-toothed gear wheels could not be produced due to a lack of proper machinery. This meant that a final drive using planetary gear reduction and pre-selector spur gearing - found to be reliable in company testing - could not be installed in the production tanks. All attempts to improve the final drive met with failure, despite the offers of a special bonus as an incentive. The housings, which initially had proven too weak and whose outer mounts had been bent out of alignment by the track's pull, were eventually replaced by stronger ones.
Panther and its Variants by Walther Speilberger
Minutes from a meeting of the Panzer Commision 23 January, 1945
Final Drive
From the front there continues to be serious complaints regarding final drive breakdowns in all vehicle types. Approximately 200 breakdowns have been reported with the 38(t). Prior to the 1945 eastern offensive there have been 500 defective final drives in the Panzer IV. From the Panther 370 and from the Tiger roughly 100. General Thomale explained that in such circumstances an orderly utilization of tank is simply impossible. The troops lose their confidence and, in some situation, abandon the whole vehicle just because of this problem. he requests an increase in efforts for the final drive, since only this way can the problem be laid to rest. With the previously intense criticism of the engine and the final drive continually playing such a roll, it is welcome news to learn that the gearbox generally enjoys a good reputation. Direktor Wiebicke claims that the Heerestechnisches Buro of the Waffenamt had for its part rejected the sun-and-planet final drive and demanded the spur wheel reduction drive. This claim led toa confrontation between Oberst Holzhauer and Oberbaurat Knonagel. Oberingenier Wiebicke clarified that for the past on and a half years there has been ongoing discussion regarding the introduction of the planetary gearing but as of yet nothing significant has been accomplished. Whereas during this entire time attempts have been made to improve the final drive, with only minimal improvement being noted. It must, however, be kept in mind that MAN, as the responsible manufacturing firm, cannot now hold other companies responsible. MAN as availed itself of all offices which have the prospect of providing a way out of these difficulties with the final reduction drive.
^ It's somewhat interesting that the Germans tried to have a French company improve the final drives.Soon after the introduction of the Panther Ausf. D into service, the steering unit exhibited reliability problems. After the war, German tank designers told their British captors that they were well aware of this defect. Their defense of the steering unit design was based on the belief that the steering brakes would outlast a vehicles transmission and final drives. Hence, it was not the serious problem to the Germans that the British portrayed in their report.
During World War II, a German prisoner of war informed his British captors that the weakness of the Panther's steering mechanism was well known. Panther tank drivers were instructed to use the auxiliary skin brakes for steering and to avoid pivot steers. He went on to say the steering unit problem appeared to be result of the overloading of the steering clutch during tight-radius and pivot steering maneuvers.
A late-war U.S. Army report noted of the Panther's auxiliary skid brake steering ability, "The skid turn feature of the steering system, which is utilized by pulling the seering lever all the way [back] and locking one track, cannot be employed at speeds in excess of approximately 8 to 10 miles per hours, and can only be used when the vehicle is in second gear, as the engine will be stalled if such a turn is made in a higher gear."
British engineers concluded that Panther final-drive units had inadequate bearings and poor housing strength. IN addition, critical areas of some gears were not hardened properly. these and other major design and manufacturing defects lead to poor final-drive reliability. Later information revealed that the Germans had approached a French firm during the war years to investigate the practicality of producing a new type of final drive for the Panther tank. The French received the assembly drawings, but nothing ever came of the proposed project.
Jaqcues Littlefield talked about what he has learned about Panther tank final drives in the process of restoring a Panther Auf. A:
"My understanding is that the final drives were always a problem. I've heard different things, for instance, that [the Germans] couldn't get the proper alloy, they couldn't heat-treat it properly, or whatever. When we test ours, the alloy and the strength of these particular gears was as good as what you could make them from today. [We] looked at maybe duplicating them, using the same physical size, but just using a stronger alloy or better treatment, and the answer we got back was that it was as good then as we can do it now.
Part of the problem with the final drives was no doubt due to the vehicle's growth in weight. It grew in weight from its original goal of 30 to 35 tons to the low 40s. I'm going to guess that what ended up happening with the final drives is that they were designed for the lower-weigh vehicle, and there wasn't the physical size [available] to where you could make the gears wider and stronger. Since they weren't able to make them wider, they just left them the way they were originally designed.
It is interesting that the American Sherman tank used double-herringbone gears in the final drives, which provides more torque capability for the given width of a final drive. The Panther uses straight spur gears, so there must have been a manufacturing limitation, as double herringbone gears were well known at the time for their ability to carry larger amounts of torque for a given width."
Panzers at War Michael and Gladys Green
Although the Panther's AK 7-200 transmission was nominally superior to the clumsy transmisison on the t-34, about 5 percent broke down within 100km and over 90 percent within 1500km in combat. The final drive on the Panther Ausf. D was so weak that the tank could not even turn whlie it was backing up, which occurred frequently in the retreat to the Dnepr River. It's two fuel pumps were probably the biggest mobility weakness in the Panther Ausf. D because they were prone to leaks and caused serious engine fires. As least three Panthers were destroyed by fuel pump-caused fires during Zitadelle, and a high proportion of the mechanical breakdowns was caused by this troublesome component. Nor did the problem go away after Kursk: the initial batch of Panther Ausf. A tanks what were handed over to the SS-Leibstandarte in Italy in September of 1943 were so problematic that every one was rejected for service.
The Panther's poor mobility forced the Wehrmacht to move units around by rail and get them as close to the front as possible before unloading. Throughout 1943, the Panther was essentially tied to conducting all major movements by rail, including the equally short-legged tiger, and units could not even move 100km without significant losses. Thus, the Panther did not meet Guderian's requirement for a tank with superior mobility, and it was the t-34's continued advantage in mobility and reliability that contributed greatly to the Soviet victory in the Ukraine in 1943.
I underlined the most interesting parts of these quotes.