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Old 05-23-2011, 01:52 PM   #1
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Default TC3 shock length & diff question

I'm working on setting up a TC3 as a spare/loaner VTA car, have a few questions for the TC3 wizards.

1) I have the composite plastic shocks, which I've installed the VCS2 upgrade kit on, and I am using a rear shock tower on the front per the more modern TC3 setup sheets.

I'm running into an issue where the shocks are just too long, especially on the front. I had to shim the front shock tower up 3mm AND take the uptravel limiters off the shock shaft (the VCS2 kit says these are required to prevent the piston from hitting the bladder) just to get enough uptravel to be able to push the chassis of the car flat to the ground. I had to remove the uptravel limiters on the rear as well. The pistons don't seem to hit the bladders, but the uptravel is still quite limited because the shocks don't compress short enough (the bottom spring retainer hits the bottom of the shock body and that's the shortest they can get).

Do the aluminum/factory/FT shock bodies compress shorter, or are they the same? If someone could compare the length or measure the compressed length in a way that I could compare to mine, that would be helpful as well..

2) any tips on being able to run the diffs looser than the manual setting without having them slip obnoxiously? They are extremely tight compared to what I"m used to on other more modern TC chassis, and even when they are tight they slip.
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Old 05-23-2011, 04:10 PM   #2
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I left the measurements in 16ths of an inch for easier comparison. I don't have digital calipers. I took the plastic shock apart so i know there aren't any internal spacers on the shaft. I don't know about the aluminum shocks, they are on an active car.

Plastic Shocks
Extended- 2 10/16 inch
Compressed- 2 3/16 inch

Aluminum Threaded Body Shocks
Extended- 2 9/16
Compressed- 2 4/16

As for the diff, unless it's a fresh rebuild, your slippage issues are from worn out balls or wrong sized balls. (My inner 13-year old is cracking up right now)

I've run the diff screw at factory setting or 1/8th of a turn looser. One thing i do differently is to run a spacer under the diff nut. That ensures that the spring gets fully compressed without damaging the plastic ears on the diff nut. You'll see the ear come within a fraction of bottoming out in the cup.
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Old 05-23-2011, 08:22 PM   #3
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Thanks. How far does your suspension compress - can you push the car down and have the chassis flush with the ground? I am having trouble even getting that far. my shocks measure the same as yours though, so I guess it's not that....

As for the diff, I did not think to check to see if the diff balls are binding in the gear (i.e. if someone crammed ones with too large of a diameter in there). the diff is very smooth when set per the manual, it's just so darned tight compared to anything else i'm used to. it doesn't really slip at the manual setting, but anything looser and they will. You can turn the entire drivetrain + motor over from one wheel without getting the diff to turn.
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Old 05-24-2011, 05:15 AM   #4
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I also have a TC3 and will be racing in the VTA series at my local track too (Toledo Ohio). Hopefully I can give you some help with the shock issues you have. I have decided to replace the Assoc. aluminum shocks that I have with XRay "clicker" shocks. They are very close to the length as the Assoc. shocks and you can have 4 different dampening settings.....very handy for tuning at the track. The XRay springs and Assoc. springs can also both be used for more spring combinations. The shock bodies are also threaded for east ride height adjustment. They are very smooth! The only thing different is the way they mount to the lower arms and shock towers. They thread a 3mm x 10mm set screw in the lower arms and shock towers. The shocks have two 3mm pivot balls to attach to the arms and shock towers.....very quick and simple. Hope this helps you out.
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Old 05-24-2011, 08:17 AM   #5
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I can compress the suspension so my chassis touches the ground.

Just off the top of my head, check the length of the CVDs... they might be bottoming out in the outdrives. There are some 200mm CVDs out there and maybe they are installed on your car with the 190mm arms.
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Old 05-26-2011, 02:12 PM   #6
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I picked up some TC4 shock ends (the ball/cup design) because the end pieces are shorter - I think that converting this TC3 to the TC4 design ends will solve the problem, although I'm still not sure why the problem exists.

I felt another racers TC3 diff and it felt very normal to me, so I definitely have something built wrong in my TC3 diffs...will tear them down and figure it out.
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Old 05-26-2011, 05:48 PM   #7
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the tc4 shock ends help a lot. I had to add a 0.085" shock shaft spacer (a translucent white shim I found in traxxas shock rebuild kids for the slash) to keep the piston from hitting the bladder, but the tc4 shaft ends still gave me about 5mm more uptravel (as measured at the wheel) because of the shortened distance from the bottom of the shock shaft to the mount point. huge help. there is still enough downtravel in the shock to allow for normal range of ride height/droop.

as for the diff, i took them apart and found both had a one bushing/one bearing combo which I think was too wide and causing the diff to bind up. I rebuilt one with both of the bushings and it worked much better.
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