I know it's a T-MAXX but ....

[True Newb]

So I picked up another nitro truck lastnight. I know it's an older 2.5 T-MAXX. Should I restore to stock or restore it with the upgrades on it? I think they are upgrades anyways. I haven't dove too deep into the history of these. I see there is a 2.5 and a 2.5R listed as models. Any way to tell which one it really is? Should I not bother with it at all? It will need new body mounts and a body and again ... the stock controller which I'm not sure which one it takes as I haven't opened the receiver box yet. Yes, the transmission is out because it has a stripped gear which I will be tackling in the near future. The transmission is also pretty aluminum. I did have this running lastnight too so there's that. LOL

 

[WickedFog]

That seems like a lot of added weight just for the bling factor. If it were mine, I would put it back to stock as far as the non-mechanical aluminum upgrades go. The aluminum tranny is a good upgrade imo, because my Jato tranny grenaded on a light endo on the rear end.

 

[Greywolf74]

I vote to keep the bling but then again I'm a bling whore

I would look into doing away with the 2.5. I believe they made a big block conversion for these once upon a time. just my .02

 

[Chubaka]

2.5 and 2.5r is in the motor, and to my memory, its the blue cooling head calling it an r.

That aluminum tank willl keep you blind with the fuel level.

The radio should be the old tq3 channel am. The new 3 channels should work, if you have reverse. A forward only conversion (foc) you van use thrme 2 channel.

If going big block, I would go 3.3 chassis and bottom brace for the longer wheelbase and stability.

If it was me, I would convert to plastic. Aluminum upgrade the f/r bulks, braces, skids, make it a functioning bueaty.

 

[cbaker65]

If you go big block ,then dont half ass it ,go with a better engine than a 3.3!..
This is what I would use along with a B-block chassy!..

https://www.ebay.com/itm/293633088077?epid=19011377352&hash=item445de55a4d:g:pEwAAOSwzclexi41

 

[Greywolf74]

If you go big block ,then dont half ass it ,go with a better engine than a 3.3!..
This is what I would use along with a B-block chassy!..

https://www.ebay.com/itm/293633088077?epid=19011377352&hash=item445de55a4d:g:pEwAAOSwzclexi41

View attachment 131188

I'm curious Baker, why a .21 instead of a .28 or even bigger?

 

[STONER RC]

I'm curious Baker, why a .21 instead of a .28 or even bigger?

The .21 is a direct drop in to the stock mount i would say. And the stock fly clutch and pinon.. Will fit it as well.
.28 got to change more

So I picked up another nitro truck lastnight. I know it's an older 2.5 T-MAXX. Should I restore to stock or restore it with the upgrades on it? I think they are upgrades anyways. I haven't dove too deep into the history of these. I see there is a 2.5 and a 2.5R listed as models. Any way to tell which one it really is? Should I not bother with it at all? It will need new body mounts and a body and again ... the stock controller which I'm not sure which one it takes as I haven't opened the receiver box yet. Yes, the transmission is out because it has a stripped gear which I will be tackling in the near future. The transmission is also pretty aluminum. I did have this running lastnight too so there's that. LOL


View attachment 131184

View attachment 131185

Nice score bud it's a older one yes.. the newer 2.5R is basically the 3.3. The older 2.5 have smaller axles and center shafts. And has reverse.You don't need the forward only gear.. just pull out the 3servo and pushing the reverse rod.. it wont come out.. I did.. never had a problem..the upgrades really aren't performance related.. more of just bling.. the tank which like above can't see fuel level. And it's just the battery box and receiver box. Looks like CVDs for axles. Can't see center shaft. And a 3.3 resonator pipe..the trans is it just a aluminum case most likely.. there wasn't any steel gears... just white ones?rest is stock.. I would get new tank. So you know how much fuel you have in there it's like 5-10$.. You can throw in a .21.. would be direct fit.. if you go bigger or to the 3.3 you will need stronger gears.. and diffs. That truck is a solid truck.. if you can get a good tune on it... the 3.3 is a solid engine.. I have it.. works well and power out the as* wheelies all day... its all about the tune and fuel your running in it...

 

[cbaker65]

I've ran the hyper 21 in my Mgt before ,it was plenty power enough along
with the 2 spd, ,but I wouldnt hesitate using the 28 either ,but you are
also talking about a Traxxas!..

 

[Greywolf74]

I've ran the hyper 21 in my Mgt before ,it was plenty power enough along
with the 2 spd, ,but I wouldnt hesitate using the 28 either ,but you are
also talking about a Traxxas!..

LOL, gotchya

 

[STONER RC]

I've ran the hyper 21 in my Mgt before ,it was plenty power enough along
with the 2 spd, ,but I wouldnt hesitate using the 28 either ,but you are
also talking about a Traxxas!..

To each their own buddy..everyone has the rite to their own opinion... But really the only problem with traxxas is thier electronics. their engines are just fine my 2.5 from 20yrs ago still works and wheelies the first maxx all day..yeah the 3.3 is not a big block and it should be but as long as you can tune a nitro good and use the rite fuel and plug and shim the head rite...its got all the power you need.. with the 2 speed trans..so
I don't understand why everyone hates on traxxas so much.. what is it about them... I know you would live to shed some light on that one

 

[Chubaka]

To each their own buddy..everyone has the rite to their own opinion... But really the only problem with traxxas is thier electronics. their engines are just fine my 2.5 from 20yrs ago still works and wheelies the first maxx all day..yeah the 3.3 is not a big block and it should be but as long as you can tune a nitro good and use the rite fuel and plug and shim the head rite...its got all the power you need.. with the 2 speed trans..so
I don't understand why everyone hates on traxxas so much.. what is it about them... I know you would live to shed some light on that one

I also have had all 3 traxxas motors. The .15, I've beaten plenty. Although I've heard alot of 3.3 issues, my 4 or 5 gallon 3.3 has been issue free. The old blsck servos were decent. The blue servos, and atleast 10 first and second gen vxl escs made me go castle, futaba, and tactic.

The only issue I have is the patent bs and bullying. They went after mcclan over an esc named max/maxx. Unsure on spelling. They claim the maxx truck line infringement. Yet castle has the mamba max and they worked together. I still want an xmaxx, but put the cen and probably an Arrma before.

 

[watertrucker]

Nice score. Your engine is the TRX 2.5 Chubaca is right, the only difference between the 2.5 and the 2.5R is that the 2.5R has a blue anodized cooling head, which Traxxas changed $70 more for That’s a good looking truck you got there. Congrats

 

[STONER RC]

I also have had all 3 traxxas motors. The .15, I've beaten plenty. Although I've heard alot of 3.3 issues, my 4 or 5 gallon 3.3 has been issue free. The old blsck servos were decent. The blue servos, and atleast 10 first and second gen vxl escs made me go castle, futaba, and tactic.

The only issue I have is the patent bs and bullying. They went after mcclan over an esc named max/maxx. Unsure on spelling. They claim the maxx truck line infringement. Yet castle has the mamba max and they worked together. I still want an xmaxx, but put the cen and probably an Arrma before.

The sad part is those are not the only lawsuit that traxxas has submitted in the last 10 yrs.. they went after a YT a small all rc review channel the rc sailors, hobbico, Arrma mcclan and more all over trade mark infigment.. its all business.. and they should have been thrown out...because they do the same thing tweak and change little thing to make their own.. problem is they patent it as there's once they tweak it.. and that's why they sue...the US where everyone sues for anything....

 

[WideOpen]

My 2.5 works just fine - why upgrade, if you don't like it, start fresh with something that is close to what you want. Just my 2-cents worth.

 

[STONER RC]

Nice score. Your engine is the TRX 2.5 Chubaca is right, the only difference between the 2.5 and the 2.5R is that the 2.5R has a blue anodized cooling head, which Traxxas changed $70 more for That’s a good looking truck you got there. Congrats

The really Sad part.. is the the 2.5r and 3.3 are basically the same engines. Same carb..The only difference is the crank shaft gas port.. piston and sleve.. But they all have the same porting in sleeves..and all the same carb.. I still have a run the original 2.5. And have the 3.3 in the truck I built last yr.. works great... both never had problems with

 

[Chubaka]

The sad part is those are not the only lawsuit that traxxas has submitted in the last 10 yrs.. they went after a YT a small all rc review channel the rc sailors, hobbico, Arrma mcclan and more all over trade mark infigment.. its all business.. and they should have been thrown out...because they do the same thing tweak and change little thing to make their own.. problem is they patent it as there's once they tweak it.. and that's why they sue...the US where everyone sues for anything....

I know all avout those and how they copied other etc. I just focused on the contradicting part trying not to go off topic, atleast not too much. I also heard they brought the parties to court in their homelandof texas, and the judge had a tenancy to side most times with the ones calling infringement.

 

[STONER RC]

The original 2.5 is different and smaller and the pro15 is is smaller all around

I know all avout those and how they copied other etc. I just focused on the contradicting part trying not to go off topic, atleast not too much. I also heard they brought the parties to court in their homelandof texas, and the judge had a tenancy to side most times with the ones calling infringement.

I really didnt want or try to go off topic .. I like traxxas and the engines never had a problem with them I say keep the truck clean everything reoil bearings and have at it...

 

[olds97_lss]

It appears yours is the 2nd gen t-maxx when they put the first 2.5 in it. It came after the first maxx that had the .15 pro engine on it. They made the arms a little wider, changed the towers, engine/pipe and throttle linkage. Probably other things, but that's what I remember. My first nitro MT was a t-maxx 2.5 from over 15 years ago.

I had that aluminum tank on mine and while it was durable, the cap would get galled from screwing it on/off over time and get hard to use, also as mentioned, you have no clue how much fuel you have. The stock tank was fine if you didn't run RPM shock towers that would flex easily and smash into the back of the tank. I ran an OFNA buggy tank on mine up where the throttle servo was and moved the throttle servo back by the engine.

The alloy trans case is nice, but not necessary if you stick with the stock engine. Not really necessary regardless what engine you run. I had one on my big block maxx, wasn't really any point to it other than it added rigidity to the chassis.

The .21 is a direct drop in to the stock mount i would say. And the stock fly clutch and pinon.. Will fit it as well.
.28 got to change more

.21-.32 big blocks have the same footprint and all of them are too big for the maxx motor mount/space without a conversion kit. The engine is wider and longer by a decent amount.

An omega 21 (big block) vs an OS18CV-R (small block, same footprint as the 2.5/2.5R/3.3):

There were some engines made as "mid-block" sized that would fit in t-maxx/revo with the stock mount or they came with their own mount, but they were shorter so the engine didn't need more space front to rear. The OS21TM, OFNA Picco 21/26, RB TM323/TM523, Sirio made one too and there were a few others. Hard to find now though.

A 3.3 would probably be ok in a maxx in stock form, especially if you ditch reverse and get the forward only kit. Reverse was really weak in those things and to make room for the mechanics, the final output gear for forward was really narrow and had a tendency to strip.

I had a big block maxx many years ago with an XTM Big Block Conversion, which came with a chassis deck, chassis rails, cvd's engine mount, pipe and header. It was intended that you use the stock flywheel/bell on it, I can't recall if it came with a standard flywheel nut or not as traxxas's is different from everyone else on the 2.5/3.3.
XTM Conversion (I had this one):

Dynamite conversion (a buddy of mine had this):

Personally, I wouldn't put a 2.5/2.5R in anything but a smaller 1/10th scale car/truck like the rustler, stampede, jato or 4-tec. It really had no business being in a "monster truck" or the revo if you ever intended on driving it in grass. Unless you liked driving really slow. For me, even the 3.3 was a dud for running in grass in my 2.5 and 3.3 revo's.

With my first revo, I got an OS18TM which was a very punchy engine that would hold a tune all day long and was very easy to tune. It seemed very peppy in a short chassis revo, but pretty tame in a 3.3 chassis revo (longer chassis). I have an OS21TM in a 3.3 chassis revo now and it's not bad. I also have an LRP28S3 in a 3.3 chassis revo and it's pretty crazy.

 

[STONER RC]

It appears yours is the 2nd gen t-maxx when they put the first 2.5 in it. It came after the first maxx that had the .15 pro engine on it. They made the arms a little wider, changed the towers, engine/pipe and throttle linkage. Probably other things, but that's what I remember. My first nitro MT was a t-maxx 2.5 from over 15 years ago.

I had that aluminum tank on mine and while it was durable, the cap would get galled from screwing it on/off over time and get hard to use, also as mentioned, you have no clue how much fuel you have. The stock tank was fine if you didn't run RPM shock towers that would flex easily and smash into the back of the tank. I ran an OFNA buggy tank on mine up where the throttle servo was and moved the throttle servo back by the engine.

The alloy trans case is nice, but not necessary if you stick with the stock engine. Not really necessary regardless what engine you run. I had one on my big block maxx, wasn't really any point to it other than it added rigidity to the chassis.


.21-.32 big blocks have the same footprint and all of them are too big for the maxx motor mount/space without a conversion kit. The engine is wider and longer by a decent amount.

An omega 21 (big block) vs an OS18CV-R (small block, same footprint as the 2.5/2.5R/3.3):

There were some engines made as "mid-block" sized that would fit in t-maxx/revo with the stock mount or they came with their own mount, but they were shorter so the engine didn't need more space front to rear. The OS21TM, OFNA Picco 21/26, RB TM323/TM523, Sirio made one too and there were a few others. Hard to find now though.

A 3.3 would probably be ok in a maxx in stock form, especially if you ditch reverse and get the forward only kit. Reverse was really weak in those things and to make room for the mechanics, the final output gear for forward was really narrow and had a tendency to strip.

I had a big block maxx many years ago with an XTM Big Block Conversion, which came with a chassis deck, chassis rails, cvd's engine mount, pipe and header. It was intended that you use the stock flywheel/bell on it, I can't recall if it came with a standard flywheel nut or not as traxxas's is different from everyone else on the 2.5/3.3.
XTM Conversion (I had this one):

Dynamite conversion (a buddy of mine had this):

Personally, I wouldn't put a 2.5/2.5R in anything but a smaller 1/10th scale car/truck like the rustler, stampede, jato or 4-tec. It really had no business being in a "monster truck" or the revo if you ever intended on driving it in grass. Unless you liked driving really slow. For me, even the 3.3 was a dud for running in grass in my 2.5 and 3.3 revo's.

With my first revo, I got an OS18TM which was a very punchy engine that would hold a tune all day long and was very easy to tune. It seemed very peppy in a short chassis revo, but pretty tame in a 3.3 chassis revo (longer chassis). I have an OS21TM in a 3.3 chassis revo now and it's not bad. I also have an LRP28S3 in a 3.3 chassis revo and it's pretty crazy.

So you have the O.S .21TM? It's not a big block it's considered a mid block. With the casing of a small block and the and the stock and bore and displacement of a big block.. But it's NOT big block.. sorry bud.. and that motor is a direct drop in fit to the Tmaxx 2.5 the ez start fly wheel clutch and bell will all fit and will mount rite into the motor mount..of the maxx 2.5... it was specifically made for the Maxx 2.5.. and the 2.5 2.5R and 3.3 are all small blocks..The 3.3 is not a big block.. the only difference is the gas port in crank shaft on the 3.3.. the trx nitros 2.5 2.5R and 3.3 are the same.. Traxxas doesn't make a big block..they are all small block engines.Why do you think they make a BIG BLOCK CONVERSION KIT.. if the 3.3 was a big block you wouldn't need that kit.. and the 3.3 has to much tourqe for the 2.5 maxx.. tku would need to change the whole drive trann from tranns to center shafts axles knuckles tie rods which then need new a arms if foung with 3.3 better to get a roller or just stick with the 2.5.
sorry man but here's some info on it all..

"OS Engines 21TM ABC .21 Engine with Manifold: 2.5 and 3.3 T-Maxx | Tower Hobbies" https://www.towerhobbies.com/produc...ith-manifold-2.5-and-3.3-t-maxx/OSMG2083.html

"How Is RC Engine Size or Displacement Measured?" https://www.liveabout.com/how-is-rc-engine-size-measured-2862919

"2.5 to 3.3 conversion — Traxxas Forums" https://forums.traxxas.com/discussion/368750/2-5-to-3-3-conversion

"TRX 3.3 too much power? Should I replace with 2.5R — Traxxas Forums"
https://forums.traxxas.com/discussion/8897078/trx-3-3-too-much-power-should-i-replace-with-2-5r

 

[olds97_lss]

So you have the O.S .21TM? It's not a big block it's considered a mid block. With the casing of a small block and the and the stock and bore and displacement of a big block.. But it's NOT big block.. sorry bud.. and that motor is a direct drop in fit to the Tmaxx 2.5 the ez start fly wheel clutch and bell will all fit and will mount rite into the motor mount..of the maxx 2.5... it was specifically made for the Maxx 2.5.. and the 2.5 2.5R and 3.3 are all small blocks..The 3.3 is not a big block.. the only difference is the gas port in crank shaft on the 3.3.. the trx nitros 2.5 2.5R and 3.3 are the same.. Traxxas doesn't make a big block..they are all small block engines.Why do you think they make a BIG BLOCK CONVERSION KIT.. if the 3.3 was a big block you wouldn't need that kit.. and the 3.3 has to much tourqe for the 2.5 maxx.. tku would need to change the whole drive trann from tranns to center shafts axles knuckles tie rods which then need new a arms if foung with 3.3 better to get a roller or just stick with the 2.5.
sorry man but here's some info on it all..

"OS Engines 21TM ABC .21 Engine with Manifold: 2.5 and 3.3 T-Maxx | Tower Hobbies" https://www.towerhobbies.com/produc...ith-manifold-2.5-and-3.3-t-maxx/OSMG2083.html

"How Is RC Engine Size or Displacement Measured?" https://www.liveabout.com/how-is-rc-engine-size-measured-2862919

"2.5 to 3.3 conversion — Traxxas Forums" https://forums.traxxas.com/discussion/368750/2-5-to-3-3-conversion

"TRX 3.3 too much power? Should I replace with 2.5R — Traxxas Forums"
https://forums.traxxas.com/discussion/8897078/trx-3-3-too-much-power-should-i-replace-with-2-5r

View attachment 131313

I never said anything about the 3.3 being a big block and I stated that the 21TM was a mid-block along with a few others I knew from a long time ago that were also mid-blocks. Some that dropped right in to the small block mount and some that didn't that came with a special mount just to fit them and I explained how you would need a kit to install an big block (which is what most people consider a typical 1/8th scale .21-.32 engine).