LST2 Transmission Problems

[LOSI_ST2]

Hi Everyone,

Just got an LST2 and ran it in high gear as it came from the factory. Then on the next tank I changed it into low and decided to do some rock crawling. On the third tank I put it back into high, except it will not engage. When I give it throttle the gears just spin but it won’t go forward. When I was changing the gears with the knob I did so in accordance with the manual.

Any ideas? Has this happened to anyone else?

Thanks,

David

I should add, that the LOW speed still works fine. Also Truck has had 6 Tanks of fuel through it, 3 were for engine break-in.

Thanks,

David

 

[LOSI_ST2]

LST2 Transmission Fixed!

After spending a few minutes over the phone with Losi's factory tech Jeremiah, I decided to break down the transmission. The transmission is pretty simple but looks well built. All metal gearing, with bearings throughout.

Since my problem was with the HI/LO knob, I worked from there. I poked around for a couple of minutes and found the issue. The gear assembly in the attached file is from my LST2. Notice the collar between the high and low gears. In the picture the collar is in the low position.

I removed the 'e' clip from the low gear side and slid the bearing, 2 very thin washers, and the gear off. The collar took 7 pounds of pressure to go in the high position (I measured, OK lame, whatever..)! This told me two things, the fit was way too tight, and the person who built it new it was an issue and still sent it off to be sold! I fixed this problem by removing the collar and machining off 0.003" off each tooth.

The high and low shift knob now works perfectly as it was meant too. Hope this helps any one that has the same issue. Also it should be noted that you probably DO NOT need to machine the collar, you could also use a file or high grit sand paper.

David

 

[jon2]

Kind of sorry as Losi said that this a better version of the HiLo selector. Can you post up a detailed process to do so.

 

[LOSI_ST2]

Kind of sorry as Losi said that this a better version of the HiLo selector. Can you post up a detailed process to do so.

*****So, you need to pull the transmission in your LOSI LST2...*****

1. Remove the truck body from the truck.

2. Locate the clutch bell and Transmission gear covers (black and clear)

3. Remove the two screws holding on the black cover, located in the 4 and 8 o'clock positions.

4. Remove the two screws holding the clear cover in place; they are kind of hidden under the large gear.

5. While keeping the servos in their "neutral" position, remove the screws from the throttle/brake and forward/reverse servo horns. Take the set screw out of the brake linkage, and pull the spring and collar off. You can now remove the linkage from the brake mechanism. Move the throttle linkage back (still connected to the servo horn) towards the air intake.

6. Flip the truck over and remove all 11 hex screws from the middle plate, keep track of their different lengths. (Two lengths total) NOTE: You don't really have to remove the middle plate, just the single screw that holds the braking mechanism in place. However, I would recommend removing the plate to get a better view of what you are doing.

7. Spin the rear wheels until you see the set screw that holds the drive shaft in place. Loosen the set screw until the socket comes loose.

8. Remove the two large gears from the transmission input shaft, keep track of the way each piece came off, number them or take a picture if your memory isn't that great. There is a small open bearing assembly, behind the washer after the spring, be careful not to damage or loose it.

9. Remove the four hex screws that are holding the transmission in place.

10. Slide the transmission forward, hold it forward and slide the rear drive shaft out of place. With the shaft now removed, remove the socket by pulling away from the transmission. NOTE: the shaft coming right out of the transmission in keyed be sure when re-assembling the truck that you align the keyed (flat) portion of the shaft with the set screw.

11. Lift the back of the transmission up and out, the front will clear now and there you have it, your transmission is out.

12. Remove all of the screws from the back end of the transmission, 10 or 11 of them.

13. If you are taking the transmission apart to fix the knob, continue on; otherwise perform whatever tasks you need to.

14. Locate the knob shaft coming down from the top of the transmission; follow it down until you find the 'fork' connected to it. Gently pull the gear assembly forward and the fork will pivot, you can remove the fork if you wish, but the fork CAN BE reversed, so make sure it you remove it that the keyed portion is meshing with the knob shaft when you re assemble, otherwise, it won't shift.

15. With the gear assembly removed locate the end with the large gear. This end has an “e” clip; the other end has a hex screw. While you can remove either end, the end with the “e” clip is easier. Pull off the clip, and remove the bearing, two very thin washers, and gear, then remove the collar.

16. Both ends of the collar are identical, or at least that it how it was meant to be. The problem is not actually with the collar, but we can easily remedy the problem by altering the collar so let’s do so.

17. With the collar off take the side that mates with it. Find a fine file in your tool box and begin each side of all the teeth. The collar is hardened, so it will take you a while unless you’re using jeweler’s files as they tend to cut well. After filing each tooth the same amount as another, try test fitting the gear with the collar. File until you can easily slip the collar into the matching teeth of the high gear. Once that is accomplished, you can now reassemble. Be sure to remove any large metal shavings for the assembly, and re-grease the gears if you cleaned them or it rubbed off.

18. Work backwards from step 15, take your time, IMPORTANT things are:

1a. The Notch in the knob shaft, that locks in place with the shift fork. Make sure it is positioned properly

1b. The Rear (and front) transmission outputs are keyed! (Flat on one side)

1c. the linkages are in their appropriate positions!

1d. the white clutch, next to the transmission, is properly packed and all parts in the transmission input assembly are in the correct order!

Hope this helps! David

 

[Chamaraw]

Thanks for the detailed description. My selector doesn't do anything either. So i guess opening the tranny would help? i tried manually shifting it, it doesn't move at all.

 

[Certified Mike]

If you noticed, the original post was made 10 years ago. I wouldn't expect any response from them. However, from what is posted here, it appears that your repair is likely going to involve removing and opening the trans. Good luck and post how you're making out, or if you need any help. Good luck!

 

[Chamaraw]

Thanks Mike. , Started off, I had bad luck with one of the nuts in the tranny and now it cannot be taken off, the screw head is gone . Any ideas how to get that removed ? Because of this i cannot remove the tranny

 

[Certified Mike]

Could you get a couple pics posted?

 

[Chamaraw]

Hi Mike, I replied you another thread. oops. We can continue either of them. But for benefit of this discussion I am putting it below.

 

[Certified Mike]

I answered on the other thread. Good luck!