David Jun's 2005 Race winning Tamiya TNX Replica build

[acprc 1529]

First, let me set the scene

Way back in 2005 TamiyaUSA was trying hard to get into Monster Truck racing. Earlier that year, Jimmy Jacobson and David Jun finished 1st and 2nd place at the 5th Annual Pro-Line Maxx Challenge Race respectively in the Small-Block class and then for the second year in a row they also finished 1st and 2nd at the Monster Madness race. Once again, a one two sweep of the podium and five laps over third place. The truly remarkable occurred when the two TRF drivers also finished 1st and 2nd in the big-block class, four laps ahead of third, using the same trucks and the same engines! The TNX dominated both classes in 2005 with good chassis tuning and some new option parts that Tamiya subsequently released. The 43508X and its racing experience also formed direction for the TNX 5.2R and the modifications that kit saw.

TamiyaUSA released its own version of the TNX labelled as kit number 43508X and it came with a pack of option parts so the user could modify the truck.

The main additions were Proline Powerstroke shocks, Proline tyres and wheels and a revised heatsink head.

 

The aim of this build is to create a replica of the racing truck that David Jun used and make it from a 43508X kit..

 

The race modifications were:

Futaba S9451 Digital servos
Pro-Line Bowtie Tyres and Velocity wheels
Ofna HD Servo Saver
Ofna engine starting Back Plate
MIP Driveshafts
Modified TNX body with a lexan wing
Relocation of the RX and battery boxes
Tamiya Fuel filter
Proline Powerstroke 6025 bypass shock set

A lexan wing on the back of the bodyshell

 

First I had to get a 43508X kit! Not sold in the UK I chanced upon one back in 2017 and snapped it up.

Very rough but the basics were there. The Proline Powerstroke shock set is expensive and hard to come by. Used sets make £140 on Ebay so I was glad this one was complete. You can also see the modified heatsink head. 

The body, wheels and tyres (rotten) were scrapped and the car went in storage.

Since 2017 I have been collecting all the extra parts I need, tyres, wheels, servos, a new body, OFNA servo saver, MIP drive cups and the OFNA engine backplate. With that now done the TNX has made it to the top of the list for rebuild.

Another Race car replica build has started! It's time to get dirty and strip it down!

[TwistedxSlayer 1303]

Proper looking forward to this!

[tamiya3speed 513]

I had a stock TNX and absolutely loved it.  Started and ran every time which is much more than I can say for my TMaxx.  Looking forward to this one.

[acprc 1529]

So today I had the daunting task of getting the TNX stripped apart. This wasn't going to be fun! Experience with the trucks has meant I use an electric drill with good screwdriver bits as there are so many screws.

This is what I started with.

No wheels, tyres, fuel tank and the engine is already detached. After about 30 mins of struggling the parts were sorted.

Parts to be inspected along with the original engine (shows the limited edition heatsink head).

Screws, metal parts and electronics. Most of the screws are badly rusted and the shafts too far gone to refurbish. I do have a lot of spares for the TNX so I think I will have most bits. The carrying handle will be restored.

Chassis plate will be restored, its dirty but not badly marked as it sits high off the ground

Chassis frames and skid plates will probably be replaced.

Upper and lower arms have bent and rusted pins in them and they are rusted solid. I have new pins and new arms so I think I know what will happen with these!

and lastly....sorry dear. Clean up of the tools and out with the vacuum!

[acprc 1529]

Update this weekend. Raided my parts and found most of the plastic parts and a lot of the hardware. Got some new screw bags from Ebay with the screws I need so hopefully will get everything else cleaned.

[TurnipJF 10243]

Good stuff! Looking forward to the next update.

[acprc 1529]

Progress this morning.

If you have seen my TGS Restoration thread here: TGS Restoration then you will know how I clean up Nitro Cars. The first step involves very hot water, soap and lots of scrubbing. I do this to get the loose dirt and oil from the parts I want to re-use to then get them in a better condition to strip

Gloves are a must!

But after approx 1 hour the parts look much much better

The chassis rails have actually cleaned up well and I will be able to reuse them. The diffs are now clean externally so will be stripped and rebuilt with new grease and bearings if required. The shocks have had an external clean ready to be dissembled.

The ProLine Powerstroke 6025-00 shocks as mentioned before were expensive when released and demand a high price today used. The quality of them shows in the way they have cleaned up.

Having looked over them externally and in an ideal world I would replace the yellow springs, the rubber boots and one blue cap. However unless I am lucky finding parts they will have to stay as is. The shock shaft will need polishing but we will see what the insides are like later.

The chassis plate is usable and most of the marks on it will be covered when the chassis is built up again. I need to get the silicone blob off that holds the starter motor cradle in place but other than that it should be fine

The carrying handle has been wet sanded after being cleaned ready to be zinc primed and repainted black. No need to spend on a new one as once painted with 4 new nuts it will look brand new.

I scored most of the screws I need by buying three Re-release Hotshot screw bags on Ebay. The TNX (as most of the TGM series) uses lots of the almost black 3mm x 12 self tappers and these bags have loads of them. Certainly more cost effective than buying the Tamiya bags with 10 in! The original screws were really badly rusted and so removing some of them damaged the heads.

Good progress for the moment, The engine is seized and so I need to get that apart, cleaned and checked and I need a few more parts like the steering rods etc. Wont be long at this rate till its going back together.

[acprc 1529]

During the week I have started rebuilding the chassis. Front and rear diffs were stripped, cleaned and rebuilt with new grease and then the front and rear bulkheads completed. These are now attached the the centre chassis plate and its starting to look like a TNX again! The chassis frames are the original ones from the kit, the skid plates and bumpers have been replaced. Two of the bulkheads are new, two used. The rear bumper isn't fitted yet as I need to add the rear steering rods first.

The Futaba S9451 servos that replace the standard Tamiya's were fitted.

The steering servo uses an Ofna HD servo saver that will be added.

The gearbox was cleaned and regreased. I'm not a fan of taking these apart unless you have to and this one feels fine, nice and smooth.

The outdrives though have some rust and will need some love

They also come with rubber covers over the pins to stop them falling out. I usually use heatshrink on these now and will show how that works once they are fitted back on.

Nice new steering rods. The chrome was really bad on the old ones and as is obvious one is bent. The fourth was missing!

The engine is going to need some love! If you have followed my other threads you will know what I am going to do to it but will document it here again.

More work this weekend

[acprc 1529]

When I first had the idea to make this replica TamiyaUSA had an article on their website. I downloaded the setup sheet at the time but not the pictures. Went to have a look in the week and the articles had gone! After contacting TamiyaUSA they got back to me and said they lost them during a server swap, panic now set in!

After thinking about it for a while I started wondering if the site had been archived one one of the many sites that now do this and low and behold it had back in 2013. I quickly downloaded what I could. The next few pictures are small because the site didn't archive the full size pictures but this is what I am trying to replicate.

The original race truck, good for cutting the air holes, body marking and the wing

The engine Ofna backplate that was used instead of the electric start and also note the original heatsink head was used. Also shows the position of the Tamiya fuel filter.

Shock position, body washers and the swap of the battery and RX box. This will help with positioning. Also I now know that the car ran white springs not the shock kit yellow ones. Another challenge. I also sure the RX box looks black and not grey. I might need to see if they used something else. Annoyingly there are no other pictures of the complete car.

and the Ofna heavy duty Servo saver

Now this photo worried me! I realised that the screws are all different. It would appear that the servo screws and at least one side of the frame have allen head screws. This will need investigating.

[acprc 1529]

After studying all the pictures it's apparent that the screw have been swapped. Ordered 100 button head allen screws the same size as the Tamiya originals.

Got the radio gear from the truck cleaned up and packed into my spares box.

[GTodd 1569]

This is so awesome!

[GTodd 1569]

I regret having baught a Tmaxx back when instead of one of these. 

[acprc 1529]

1 hour ago, GTodd said:

I regret having baught a Tmaxx back when instead of one of these. 

The T-Maxx is a great truck as well. I run one as a runner and they are great fun. A few simple mods and it flies.

[acprc 1529]

1 hour ago, GTodd said:

This is so awesome!

Thanks, tedious job of swapping all the screws this weekend!

[acprc 1529]

So spent quite a while swapping all the kit screws to the allen head ones. Thinking about it I bet TamiyaUSA used TI ones on the race car.

Then replaced the kit rubber boots on the gearbox outdrives with heatshrink

and fitted the gearbox and driveshafts into the chassis (using the allen head bolts of course!).

[acprc 1529]

So today the chassis looks like this, its starting to look like a TNX again.

Got the Ofna HD servo saver fitted and the steering rod. It took me 18 months to find the servo saver in blue like the original. The race car had black 6mm adjusters fitted so I copied them. The TNX is one of the only Tamiya kits to have grey adjusters but the black are used on lots of kits. I would imagine when the drivers asked TamiyaUSA for more the black came to hand quicker and that's possibly why black are fitted.

Mounted the radio box and battery box in the opposite positions to how they are normally as per the race truck. Didn't want to drill the chassis so mounted them with screws already in place. They placement looks the same as the race truck so I am happy,

Also got the rear arms mounted (used black 6mm's again) and that allowed me to fit the rear bumper and skid plate.

I think the next thing will be fitting the rear MIP drive shaft's and then starting to tackle the engine. 

[acprc 1529]

Had a look at the engine with a view to stripping it down.

 

Took about 15 mins but one head bolt needed some persuasion!  

Top left is parts to be individually cleaned or inspected for re-use, bottom left are parts for the bin. No need to use old screw, gaskets or glow plug. Right hand side is parts to be cleaned. Crank and piston are still in there at the moment and will need some heat to release. Piston liner came free.

[speedy_w_beans 4282]

It's amazing how well everything is cleaning up; the chassis shots are beautiful!

[acprc 1529]

43 minutes ago, speedy_w_beans said:

It's amazing how well everything is cleaning up; the chassis shots are beautiful!

It is indeed coming up nicely. Really fine wet and dry makes a huge difference on the surface appearance. 

[Tizer 607]

On 2/2/2020 at 6:21 PM, acprc said:

It is indeed coming up nicely. Really fine wet and dry makes a huge difference on the surface appearance. 

On the plastic too? What grit? The parts indeed look so much better now than the 'before'

[guggles 295]

An update to the TNX race build is a perk to my day

 

When these trucks first hit the market I thought it was almost like a clone of the tmaxx design. I would have loved to get one but I had an Emaxx and the parts availability where I am in the states was so poor compared to traxxas it wasnt even funny.  It would be quite cool to see the tamiya truck beat a pack of tmaxxes like this one did. 

The engine is crazy dirty  

[acprc 1529]

11 hours ago, guggles said:

An update to the TNX race build is a perk to my day

 

When these trucks first hit the market I thought it was almost like a clone of the tmaxx design. I would have loved to get one but I had an Emaxx and the parts availability where I am in the states was so poor compared to traxxas it wasnt even funny.  It would be quite cool to see the tamiya truck beat a pack of tmaxxes like this one did. 

The engine is crazy dirty  

Glad that you are enjoying the updates. I know my nitro passion isn't to everyone's taste but its good to get feedback on the threads.

I have had a T-Maxx for many years and even in its first form its a capable truck and great fun. The TNX is also one of the best trucks Tamiya has made in basic form. I do need to organise a TNX 5.2 or Nitrage 5.2 runner though!

The engine is bad but certainly not the worst I have seen. I have left it to this weekend due to it needing extra work. The crank is seized and I am betting I will need to replace bearing and/or the crank. We shall see

[mtbkym01 4246]

There are a few of us “Nitro” guys here who keep a keen eye on your threads. I have 3 Nitro projects for the future myself.

wont be to the “next level” that you take your builds too though, great work

[Collin 2047]

Nitro for president : ) We all know Lithium is a very rare good, so better safe Lithium and burn Nitro. Our kids will thanks to us.

I love this detailed restorations threads with really good pictures and a bit of investigation very much. Thanx for that.

[acprc 1529]

1 hour ago, mtbkym01 said:

There are a few of us “Nitro” guys here who keep a keen eye on your threads. I have 3 Nitro projects for the future myself.

wont be to the “next level” that you take your builds too though, great work

Thanks for that. Shout if I can help when the projects make it to the top of the pile