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Discussion Starter · #1 ·
Anybody by chance have a 99-04 400ex tranny apart? Found this in the bottom of my motor and trying to figure out which gear lost a tooth.
Also, how bad would it be to take it on one trail ride before fixing?
Nothing else in the motor oil and screen was clean. Bike ran fine and still sounds good.
Any advice is greatly appreciated!
 

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It's nearly impossible to identify which gear it's off of without taking the transmission apart, but gear #4 (mainshaft 2nd gear) is the most frequently damaged and failed gear in the entire tranny. If a replacement is found, gear #5 needs to be replaced also.

Product Font Auto part Diagram Engineering


All the parts with $0.00 prices are no longer available

REF.
NO.​
PART NO. / DESCRIPTION​
dealerorders.com's
PRICE​
TRX400EX
A9 A​

1​
23211-HN1-000
MAINSHAFT, TRANSMISSION (12T)
137.38​
1​

2​
23220-HN1-000
COUNTERSHAFT, TRANSMISSION
0.00​
1​

3​
23411-HN1-000
GEAR, COUNTERSHAFT LOW (35T)
0.00​
1​

4​
23421-HN1-000
GEAR, MAINSHAFT SECOND (16T)
0.00​
1​

5​
23431-HN1-000
GEAR, COUNTERSHAFT SECOND (31T)
0.00​
1​

6​
23432-HM3-670
BUSH (22X25X10)
11.04​
1​

7​
23441-HN1-000
GEAR, MAINSHAFT THIRD (19T)
0.00​
1​

8​
23451-HN1-000
GEAR, COUNTERSHAFT THIRD (28T)
0.00​
1​

9​
23452-HC0-000
BUSH, COUNTERSHAFT THIRD
17.78​
1​

10​
23452-KCY-670
BUSH, COUNTERSHAFT THIRD
14.09​
1​

11​
23461-HN1-000
GEAR, MAINSHAFT FOURTH (22T)
78.74​
1​

12​
23471-HN1-000
GEAR, COUNTERSHAFT FOURTH (26T)
0.00​
1​

13​
23481-HN1-000
GEAR, MAINSHAFT FIFTH (26T)
0.00​
1​

14​
23491-HN1-000
GEAR, COUNTERSHAFT FIFTH (26T)
0.00​
1​

15​
23502-KA2-000
BUSH (20MM)
25.38​
1​

16​
23512-KEA-000
COLLAR, SPLINE (22X14)
19.16​
1​

17​
23521-KCY-670
PLATE, BEARING SETTING
12.31​
1​

18​
23801-HN1-000
SPROCKET, DRIVE (15T)
0.00​
1​

19​
23802-KAE-870
PLATE, FIXING
4.62​
1​

20​
90001-MA2-770
BOLT, SOCKET (6X16)
3.31​
2​

21​
90118-958-003
BOLT, FLANGE (6X12)
3.22​
2​

22​
90451-KY1-000
WASHER, SPLINE (22MM)
3.80​
2​

23​
90451-KY2-000
WASHER, SPLINE (25X31X1.5)
3.80​
1​

24​
90454-KF0-000
WASHER, THRUST (17MM)
4.36​
2​

25​
90454-428-000
WASHER, THRUST (20MM)
2.40​
1​

26​
90455-ML7-000
WASHER B, THRUST (22MM) (BLUE)
4.84​
1​

27​
90456-MA6-000
WASHER, THRUST (25MM)
2.40​
3​

28​
90601-107-000
CIRCLIP (25MM)
3.71​
1​

29​
90601-329-000
CIRCLIP (22MM)
2.42​
2​

30​
91003-KCY-671
BEARING, BALL (25X52X13)
0.00​
1​

31​
91004-KN5-671
BEARING, RADIAL BALL (17X44X12)
0.00​
1​

32​
91005-KF0-008
BEARING, RADIAL BALL (62/22)
38.87​
1​

32​
91005-KS4-003
BEARING, RADIAL BALL (62/22)
38.87​
1​

33​
91008-KN5-671
BEARING (6203)
0.00​
1​

33​
91053-HB3-771
BEARING, RADIAL BALL (6203)
0.00​
1​

34​
91203-KCY-671
OIL SEAL (25X35X5)
7.11​
1​

35​
91204-HN1-003
OIL SEAL (17X34X4.5)
4.22​
1​


Also, how bad would it be to take it on one trail ride before fixing?
The worst that can happen is it will break and lock up the transmission, but it's not fixable if you take it apart, so take your chances - it's junk either way.
 

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Discussion Starter · #3 ·
The worst that can happen is it will break and lock up the transmission, but it's not fixable if you take it apart, so take your chances - it's junk either way.​
[/QUOTE]
Not fixable? You mean Because the parts are discontinued?
 

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Yes and used parts are almost gone too - the 99-04 TRX400EX is a relic - if you take it apart and can't get the parts you need, you can try to part it out, but don't expect much. Try to sell it as is and let the next guy find out what problem it has. If you are lucky a noob will buy it for 2 grand and you can get an o6 or newer, they will still be around for awhile. If it's special to you because of mods and performance parts, get a newer one and swap the special parts then sell the relic.

The truth hurts, but like Windows ME, XP and 7, the 99-04 TRX400EX is no longer supported by Honda and it's time to upgrade.
 

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Discussion Starter · #5 ·
No I appreciate the honesty. I was looking at some used trannys on ebay. If I decide to try and fix it it would be more for the learning experience. I'm also debating selling it since my kid would rather have a dirt bike anyway
 

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Just be cautious of the used trannys - I have one - it's missing #4 - I sold #4 for $150 and it was perfect - I would sell the rest of the transmission for $100 - if you take it apart, maybe you will get lucky and it will not be $4
 
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