Tatra MTVR Prototype M923A1 - Tatra 815 Frankenstein

gearhead

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I wanted to share an interesting vehicle that I acquired out of Barstow/Yermo a few years ago for all you Tatra and M939 fans. From what I’ve researched this truck was put together to evaluate the Tatra system as an option for the MTVR vs Oshkosh. The truck had "test vehicle" stenciled on the door and had heavily modified brackets in the bed and bolted to the frame which I assume were used to apply load or mount test equipment. It also looked to have an early version of CTIS installed as well.


How was this put together?

From what I can tell.....Driveline and suspension are from the Tatra 815. To power this rig a N-14 Cummins mounted to an Allison HD4560P 6 speed trans. It was a tight fit for sure, and the cab and hood have been lifted 3 inches to accommodate the taller motor. Additionally, there is an air starter to get this thing going - not sure why but probably to fix clearance issues with an electric starter. Lots of switches that I’m still figuring out but it appears I can control different sets of axles from the cab. Pictures better tell the story:)

Ignore the generator and air compressor mounted on the new pictures- those are so I can get it started if I lose air pressure and are not original. I will take engine and interior photos and anything other requested and post more later.
 

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fuzzytoaster

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I remember watching that green one sell on GL years ago. It sparked the threads about the "M939A3" program that was scratched to fund the MTVR and FMTV series.

Do share more photos! What's on the data plates?
 

Rusty Loads

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Looks like it's running them kooky 16:00 R21 tires like I'm using (original Tatra wheels) w/tubes. Don't forget the oil in the hubs...It probably has planetary reductions...very spendy to fix.
 

gearhead

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Looks like it's running them kooky 16:00 R21 tires like I'm using (original Tatra wheels) w/tubes. Don't forget the oil in the hubs...It probably has planetary reductions...very spendy to fix.
Yes im not really a fan of the 16R21s but there does not appear to be many other options for the 16R. The rims look to be a custom split rim version without a tube which were relatively easy to mount the tires on. They feel more like a tire for a loader or other piece of equipment. Im using standard gear oil in the hubs is there a different weight Tatra requires?
 

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gearhead

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Ramona, Ca
I remember watching that green one sell on GL years ago. It sparked the threads about the "M939A3" program that was scratched to fund the MTVR and FMTV series.

Do share more photos! What's on the data plates?
Data plate is pretty standard for an m923a1 doesnt look like they changed it, from the frame to the tatra unit it has "MTVR" stamped on them but thats about it
 

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gearhead

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That is one cool truck! I'm sick of shifting gears! I'd love to have an auto in mine. What is it like to drive?
The automatic works well and the N-14 sounds great. Without weight on the suspension it bounces down the road pretty good, but the power to weight ratio and gearing are what I wish all the 939 series trucks originally had.
 

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Rusty Loads

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I have some friends on the Canadian Oil patch running 2 of the 8x8 Tatra. They say nothing will keep up to them in the bush in the winter. It's a suspension many other trucks wish they had. I wish I had a tubeless version of this stock wheel. The whole tube thing was a pain in keester. As a side note I believe most Tatra trucks running the larger diameter tires such as what you and I have (16:00 R21 or R20) have some kind of a body lift on the cab so the tires don't touch. I have a double cab unlifted and have not touched them yet. Obviously cab height not an issue for you as the whole truck is custom built. It looks like you do not have CTIS which makes the bespoke wheel thing a lot easier.
With regards to hub oil my manual for the 815VT lorrie as they call it specifies SAE80W. From memory (hope it's working) I'm running Amsoil Severe gear in the closest viscosity to that. I've done long road trips and no appreciable heat buildup (I always give them a pat when I stop to take a break)
Here is a pic of stock wheel and some notes from manual.IMG_1316.JPG
 

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Rusty Loads

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You probably could switch to 16:00R20 Wheels and tires. I tried some Alu Hutchinsons...they bolt up but the only problem was marrying it to my CTIS. So I chose the path of least resistance and picked up these 21's cheap and kept stock wheels. If you don't have CTIS the switch may be quite easy providing offset is similar.
 

Rusty Loads

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Now that I look at some of my test pics (it was a while ago)...there is another problem with the US style military wheels..there are a few different ways of centering the wheel and the Tatra uses a different style (of course). So you are looking at wheel mods and stud/nut differences. Hope that helps.
 

gearhead

New member
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16
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Location
Ramona, Ca
I have some friends on the Canadian Oil patch running 2 of the 8x8 Tatra. They say nothing will keep up to them in the bush in the winter. It's a suspension many other trucks wish they had. I wish I had a tubeless version of this stock wheel. The whole tube thing was a pain in keester. As a side note I believe most Tatra trucks running the larger diameter tires such as what you and I have (16:00 R21 or R20) have some kind of a body lift on the cab so the tires don't touch. I have a double cab unlifted and have not touched them yet. Obviously cab height not an issue for you as the whole truck is custom built. It looks like you do not have CTIS which makes the bespoke wheel thing a lot easier.
With regards to hub oil my manual for the 815VT lorrie as they call it specifies SAE80W. From memory (hope it's working) I'm running Amsoil Severe gear in the closest viscosity to that. I've done long road trips and no appreciable heat buildup (I always give them a pat when I stop to take a break)
Here is a pic of stock wheel and some notes from manual.View attachment 797677
Great Thanks! Really helpful info 815 info in english seems to be difficult to find
 

Karl kostman

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THIS is one the the coolest things I have seen in a LONG time!! I am a huge Tatra fan and own a 939 series truck melding these two together has got to obviously produce a BIG winner ! Love the truck and cannot wait to hear more!
Karl
 
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