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(14-07-2020) [] HSTV-L Transmission Incorrect Functionality

1. A detailed description of the issue you have encountered. It is also important that you describe how we can reproduce the issue, if you are able to reproduce it.

The real HSTV-L that was tested in the 80's had four forward gears and a single reverse gear in a an automatic X-300-4A transmission with an auto lockup torque converter. From my understanding, the HSTV-L is implemented with eight forward gears and two reverse gears due to the presence of a torque converter on the vehicle, adding one extra gear in between each gear shift. As such, the real R - N - 1 - 2 - 3 - 4 range is implemented as R2 - R1 - N - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8, so gear shift 1 - 2 on the real vehicle is implemented as gear shift 2 - 3 in war thunder.


The HSTV-L, when fully upgraded, in simulator mode, with reference modifications selected, and the transmission mode set to manual, hits the RPM limiter of the turbine engine and is forced to change gear from gear 1 - 2, in War Thunder: 2 - 3, at 10km/h or 6.25mph. Testing in the exact same way for gear shifts 2-3, in WT 4-5, the RPM limiter is reached at 18km/h or 11.25mph. For the gear shift 3-4, in WT 6-7, the RPM limiter is reached at 30km/h or 18.75mph. Screenshots are attached under Section 5.


The same data, schematically displayed:

1st-2nd  implemented as 2nd-3rd at 10km/h which equals 6.25mph

2nd-3rd  implemented as 4th-5th at 18km/h which equals 11.25mph

3rd-4th  implemented as 6th-7th at 30km/h which equals 18.75mph


The gear shifts as implemented in the game hinder the performance of the vehicle, especially on rough terrain as specified in Spookstons bug report here;


For a vehicle designed with agility and high speed maneuverability in mind, this is a severe disadvantage. Additionally, and most importantly, it is incorrect and inconsistent with the HSTV-L's X-300-4A transmission. The gear changes should occur at different speeds than at those that are implemented.

2. If applicable, the full name(s) of the vehicle(s) affected.


High Survivability Test Vehicle - Lightweight


3. A detailed description of the fix you suggest. Provide sources including reference that underline your position.  This is up to the discretion of the Technical Moderator handling the report, however the number of sources required depends on the type of source presented:


I have located an unclassified report called "Propulsion System Technology for Military Land Vehicles", performed by The "Institute for Defense Analyses" [1], that tests a variant of the X-300-4A transmission with the torque converter removed (designated the X300), using a Garrett GT601 engine.

The GT601 and LTS101-650 are Comparable


I have found another study on the GT601 engine presented by the Garrett corporation [2], the manufacturer of the GT601. It is an engine of the same design, being another gas turbine engine. It also has similar output power as Garrett specifies the power output on page 425 of source [2], between 450 and 650hp. 


Page 425 of source [2]


The GT601 engine has the same RPM limit (3000rpm) as specified in the game for the Avco Lycoming LTS101-650 turbine engine on the HSTV-L. 

Page 433 of source [2]


The engine equipped and tested in study [1] is therefore comparable in both power output and max rpm, and should have similar performance and output figures.


In source 1, the study on Propulsion System Technology for Military Land Vehicles, the authors have two diagrams on page number 84.

General Efficiency Diagram for the X300 Transmission


The first shows the relationship between the vehicle speed and its output power over gross power (track horsepower/maximum engine shaft horsepower).



Page 84 of source [1]: The solid black line indicates the X300 transmission on the GT601 engine.

This diagram needs to be considered with the fact that it represents a different engine, and a modified gearbox. The gearbox here does not have a torque converter with auto lockup, as the HSTV-L does. The gearing ratios should however be the same. So the peak output power ratios could be used here (due to the auto-lockup), while the minimum output power ratios need to be taken with some grain of salt (as the torque converter would have some inefficiency). The power ratios should look more like the ratios shown for the AMX1100 transmission, tested on an M1 Abrams in this study from what I understand.

As can be readily observed from this diagram, the gear changes occur at between 15 and 20mph (approximately 17mph), 20 and 25 (approximately 22mph) and 30 and 35 (approximately 34mph). The vehicle speed at these gear changes is drastically different than is implemented in the game for the HSTV-L.

Power Transfer Diagram for the X300 Transmission


The second diagram shows the relationship between output power/input power (track horsepower/shaft horsepower) and the vehicle speed. 


Page 84 of source [1]: The solid black line indicates the X300 transmission on the GT601 engine.


This diagram is almost certainly not in and of itself relevant without some consideration being paid to the fact that it is a different engine, with a modified gearbox. The effects of the torque converter with auto lock up would cause an increased efficiency in the valleys in the diagram, and perhaps would be most notable in the low efficiency regions between 7 and 15mph, and below 5 mph. But I have added it as I thought it may still be useful for the developers to assess the performance that the vehicle should have.


Conclusion and Suggested Changes


Even assuming there may be discrepancies in the size of the drive sprocket leading to some inaccuracy of this data as applied from the MICV to the HSTV-L, there is a substantial discrepancy in when the HSTV-L changes gears that cannot be ignored, leading to a substantial loss of off-road mobility in the game.

For instance, the gear change from 7-8 currently stalls the engine at less than 45km/h or 28mph, due to the way all of the gears are placed before 28mph. This bug report would also correct that issue.

The vehicle ground speeds at which the engine reaches its maximum rpm are therefore suggested to be changed such that;
1. When in gear 2, the vehicle should hit 3000rpm at 17mph, such that it changes gears from 2-3 at 17mph, rather than the current 6.25mph.
2. When in gear 4, the vehicle should hit 3000rpm at 22mph, such that it changes gears from 4-6 at 22mph, rather than the current 11.25mph.
3. When in gear 6, the vehicle should hit 3000rpm at 34mph, such that it changes gears from 6-7 at 34mph, rather than the current 18.75mph.


The gear changes 1-2, 3-4, 5-6 and 7-8 are added as a substitute for the missing torque converter functionality in the game, so the devs would know where to place the gear change relative to the documented gear changes better than I. They should however also be changed to be intermediate the suggested gear changes above.




I would have added the documents as attached files, as I noticed under "armor 3d and damage model" (did not think to look there, as this is none of those things) it said to attach the files directly. Unfortunately, the forum only allows me a maximum of 43.16mb, and the files are much larger combined.

[1] Propulsion System Technology for Military Land Vehicles, by the Institute for Defense Analyses. Retrieved 21.06.20.



[2] ITI GT601: A new Approach To The Design of Vehicular Gas Turbine Power Units by Geoffrey Woodhouse and the Garrett corporation. Retrieved 21.06.20. Page 425 onwards.


5.  Please attach screenshot(s) showing the issue, as well as the client replay file and the server Replay.

Screenshot of the HSTV-L redlining at 3000rpm in gear 2 (IRL gear 1) at 10km/h or 6.25mph.

Screenshot of the HSTV-L redlining at 3000rpm in gear 4 (IRL gear 2) at 18km/h or 11.25mph.

Screenshot of the HSTV-L redlining at 3000rpm in gear 6 (IRL gear 3) at 30km/h or 18.75mph.

I am not sure how to attach a replay and server replay from a test drive. If they are required I will add them if I can figure out how, if not, I hope these screenshots are sufficient.

6. Attach the Client Log (CLOG) of the session in which the error occurred. If the problem is persistent, attach the latest one available.


Not applicable. (If I am incorrect, please do not hesitate to contact me and I will update the report ASAP)


7.  Attach your system's current Dxdiag Log.


Not applicable. (If I am incorrect, please do not hesitate to contact me and I will update the report ASAP)


8.  If possible, link a short video showcasing the issue.  If the issue is interface related - please include video or screenshots of the interface issue.


I do not have the ability to record my gameplay at the current time. If the screenshots and my description does not explain the problem adequately, please contact me and I will try to correct it as soon as possible.

Edited by SigneOtter
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Your report has been submitted.

For any questions feel free to PM me or any other technical moderator.

Thanks for your time and effort

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  • LordMustang changed the title to (14-07-2020) [] HSTV-L Transmission Incorrect Functionality
  • 2 months later...



For a change to happen, gearbox ratios need to be provided. If you find documentation that contains this, please create a new report with this information or PM it to me, so it can be submitted.



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