Hi Nikolay! This sounds like it could be a blipper issue (because you are hearing the pneumatics, but it wont downshift under load) Did you check the blipper wires as we discussed? Also you can have someone watch the blipper to see if it is actuating when initiated.
Yes, we looked at the data and it appears to blip. Perhaps not always sufficiently or consistently but it blips. What makes it extra confusing is that it seems fine if we jacking it up and go through the gears, or if I test in in the pits. The problem appears when the car is driven hard on track...
Nikolay - in my case, the shift never initiated because the wiring harness was clearly torn. In your case, and Charley will probably add in, I think yours sounds like a potential sensor issue. I went through some diagnostic steps, see the attached here related to the downshift -
Ensure blip is between 20- 35% (it doesnt say of what)
Also check it is blipping mechanically at the actuator end
Just to add to the above have you checked the setting for your actuator? It could be that the actuator is not moving enough for the down change under load.
Also check that the rose joint on the gear lever is not worn and the actuator bearing on the other end. Also that the actuator is mounted correctly.
No, I've had the problem going down to 3rd, 4th and 5th. It's intermittent and seems to get worse as the session progresses, thought that may just mean that I build up speed as the session progresses...
Nikolay, Another thing that could be affecting the blippers ability to function properly is your throttle cable. It could be out of adjustment and not letting the blipper blip the throttle enough to get a good gear change. It could also be starting to fail which could restrict movement. I would inspect the throttle cable at both ends of the sheathing because this is where the cable tends to fail. If that is good, you can remove the cable from the throttle body and verify that it has smooth movement through the sheathing. Here are some instructions on how to set up and verify the throttle cable is working properly. Note that the graphics on the computer screen may look a little different on your screen, but the logic applies.
Thanks guys for all of the leads and thank you Charley for putting together this site! I'll forward to my mechanic and hopefully one of the leads gets us to the bottom of the problem. Will keep you updated...
Nikolay one of the may reason it get difficult to down shift is because the gearbox is loaded , its a must that the Blipper blip to unload the gear dogs.
Otherwise. the decelerations put a tremendous load on the gearbox and the actuator doesn't have the force to overcome that and specially as you get faster during the day. check to make sure the blipper is working and that you have the right amount of blip..
Nikolay followed up with me today in an email and said that he believes he found the issue. I wanted to post the information here so others could benefit from what he found. The bearings on on both sides of the actuator are warn. That much wear could definitely impact the cars ability to shift properly. Here is the video he sent me of what he found.
Wow -- that kind of wear doesn't seem normal... I'd keep digging and inspect the gearbox internals to make sure all is well there. That much wear tells me that the gearbox isn't shifting very well and banging the dogs. Charley, your original diagnosis of blipper issues still looks good to me.
You could very well be right! I bought my car from Charley (speak of provenance!) so I know it was meticulously maintained. I've done 15 or so track days since which doesn't seem enough to result in this kind of damage unless there is some other underlying problem...
Also check that the rose joint on the gear lever is not worn and the actuator bearing on the other end. Also that the actuator is mounted correctly.
This is fairly common, hence me mentioning it above. It does not normally point to internal damage.
The rose joint is a fairly common karting one so can be picked up easily. On the other end the bearing is an off the shelf item, providing that the housing is not damaged, you can remove the clip and then bearing. Place the insert in the new bearing and reinstall.
This should be checked regularly as part of your maintenance on an SR3.
Nikolay, I just spoke with one of the technical experts at Spring Mountain and he told me that this is very common and is not indicative of transmission failure... They just wear out. Spring Mountain routinely change them every 80 hours to prevent failures. They have them in stock and the actuator is $245.70 and the rod end is $15. They also suggested double checking the throw to make sure it isn't too much in either direction.
Please consider purchasing the parts from SM since they were so supportive in sharing their knowledge.
