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Old 07-28-2007, 11:28 AM   #1
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Default Launching / take-off straight

I'm having some issues with power control on my Stampede. I have a MM5700 setup and a few bashing upgrades. I cannot, for the life of me, launch the car straight. It always wants to pull hard to the left after a foot or two, then straighten out. It can be tricky on pavement as well, as when the truck will wheelie, it'll "walk" on the wheelie bar and then cartwheel. Obviously easier application of the throttle will alleviate this to some extent, but with WOT on a stock brushed truck, it'll wheelie in a straight line with no problems. Here's what I've changed/upgraded:
  • RPM bearing carriers and 5x11 Team Blue Star bearings all around
  • Added 2.2" wheels and Masher 2k tires all around (replacing stock 2.8 talons)
  • Hitec 925MG servo
  • Kimbrough gas servo saver
  • Repacked diff with marine grease
  • No excessive play on yokes
  • Lugnuts not over tightened
  • Rebuilt stock shocks w/aluminum caps and fresh 30wt oil
  • Medium preload spacers all around
  • New RPM rear arms, shocks in outermost holes

I'm almost certain this is drivetrain related, but I cannot for the life of me figure out what is the problem. I bought the truck used, so I'm not sure what the previous owner may have done. Any suggestions?
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Old 07-28-2007, 11:42 AM   #2
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shocks all the same length? chassis level side to side? shock springs set the same? is the chassis tweaked? any binding in the suspension? are the steering arms the same length? tires straight, or have good toe in or out? any binding in the drive train? bearings all roll smooth?
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Old 07-28-2007, 01:14 PM   #3
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if u dont race it, get a Futaba G190 gyro(its just like hpis d-box), u can adjust it from 0%-100% bacicly it keeps ur car stright no matter what even with bald tires

i have one an use it for my t3 and my brushless 8ight T... ull love it
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Old 07-28-2007, 01:36 PM   #4
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g

Last edited by OG RC 10T; 07-29-2007 at 07:18 PM. Reason: incorrect suggestion\
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Old 07-29-2007, 11:32 AM   #5
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Quote:
Originally Posted by mugenlife View Post
shocks all the same length?
Yes, all identical.
Quote:
Originally Posted by mugenlife View Post
chassis level side to side?
See for yourself. I think it sits just a c-hair lower on the right:

Quote:
Originally Posted by mugenlife View Post
shock springs set the same?
Yes, identical springs left and right, same preload spacers on each, same mounting points for shocks.
Quote:
Originally Posted by mugenlife View Post
is the chassis tweaked?
I broke the original chassis in a front end crash a few weeks ago and replaced it with a factory fresh one.
Quote:
Originally Posted by mugenlife View Post
any binding in the suspension?
Not that I can tell. No rubbing.
Quote:
Originally Posted by mugenlife View Post
are the steering arms the same length?
Yes.
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tires straight, or have good toe in or out?
Cannot adjust toe in the rear. Front seems ok with just a bit of toe in on each side.
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any binding in the drive train?
I don't think so. I took apart the transmission again yesterday and packed the diff with silly putty at the advice of my LHS. The car is now a handful to drive (as expected) and it now pulls even harder to the left, I think. I'll save this for rock crawling and hill climbing.
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bearings all roll smooth?
Yes, replaced them all with 5x11 Team Blue Star sealed bearings. Wheels will spin "forever" in the front, and evenly in the rear.

Gyros are tasty, but I don't think they belong on my truck until I can straighten things out without it. This definitely seems like a power application and not steering.
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Old 07-29-2007, 03:25 PM   #6
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i bet its ur diff......

try rebuilding it..
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Old 07-29-2007, 04:45 PM   #7
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Traxxas sells the diff as a unit according to their exploded diagram. I've already taken apart, cleaned, and relubed the diff twice. By rebuild do you mean replace?

Oops, read the diagram wrong. Part 2382 is the package of gears and shafts for the diff.
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Old 07-29-2007, 05:19 PM   #8
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sounds like the thrust bolt, which is what bolts the outdrives together on the diff is loose. well to loose for that much power. son when you hit the throttle it is slipping and one wheel is spinning faster then the other until it locks up and then both wheels are spinning together. with that much power you need to run it a bit tighter then normal. since you have driven it this way already you will most likely need to replace the center diff gear,diff balls, and the thrust bolts assembly completely. after that it should be better with better throttle control also.
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Old 07-29-2007, 05:32 PM   #9
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looks like right rear upper camber link is at a different angle than the left.
Maybe it's an optical illusion you might want to also measure all 4 corners of the chassis to the table to see if chassis is tweaked. Try some different tires too.
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Old 07-29-2007, 08:22 PM   #10
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AzBobby, I'm not sure what part you're talking about. I'm not running a ball diff. This is the standard Stampede planetary differential.

I'm going to try again tomorrow, reversing the rear tires. I also have a set of Masher 2000s on separate wheels that I've tried with the same results.
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Old 07-30-2007, 03:54 PM   #11
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Quote:
Originally Posted by beatle View Post
AzBobby, I'm not sure what part you're talking about. I'm not running a ball diff. This is the standard Stampede planetary differential.

I'm going to try again tomorrow, reversing the rear tires. I also have a set of Masher 2000s on separate wheels that I've tried with the same results.
sorry about that, didnt know that truck uses a planatery. even still the center gears in that set up my be rounded off a bit causing the same results. also someone else posted that the rear camber links where they are mounted at the hubs are in different locations. that would also give you some troubles but shouldnt cause your truck to shoot to one side or the other from take off.
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Old 07-31-2007, 03:54 PM   #12
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Replaced the stub axle and reversed the tires. Things definitely seem to be worse. It pulls so hard to the left that I cannot wheelie without it starting to cartwheel. I have no idea how this is possible with a basically locked diff.
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Old 08-05-2007, 07:49 PM   #13
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I rebuilt the diff after stripping all the planetary gears with the putty. The truck still does not go straight. It is impossible to get it to go in a straight line without fishtailing back and forth. How much more stuff can I replace?
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Old 08-06-2007, 06:54 AM   #14
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*edit picture post*
Attached Thumbnails
Launching / take-off straight-scaled.jpg   Launching / take-off straight-img_0380.jpg  

Last edited by mattnin; 12-28-2011 at 10:04 PM.
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