quote:

Originally posted by Ron Gusack:
How do you suggest replacing factory wires to the MSD box, tach and Racepak?

No replacing factory loom wiring. Inspect the wires and replace ends.

I can't see what you're working with, but here's something to try temporary to see if there is resolve. Attache all 4 ring terminals together using a threaded screw and nut. Tape it up with electrical tape to insulate (it's temporary). Don't use the fuse panel.

Is the plunger mushroomed at all? Have you checked the shifter linkage?

Had issues with this myself. Shifter adjustment is important to preventing the 1st to third.

The plunger looks good to me. I haven't crawled under it and looked at the linkage. The timeline of it working and not working leads me to believe that it's something with the 4 tach signal wire terminals or the junction I used for them. I've made a new junction point to see if that fixes it but there's rain predicted for this weekend so I probably won't get out.

Screwed the 4 terminals together and wrapped with electrical tape and hang it in mid air. Set it to shift first to second at 6100 and then 6200 for second to third. This shifting problem was fixed for nine runs over a few weeks. Last Friday is shifted great for the first Q run but I needed some more ET so I moved the shift point to 6500. Q2 it shifted 1 to 3 and did that for the next five runs. I can't see how moving the shift point would cause it to mess up again but that's what seems to have happened. Pulse setting was at 60 for all runs. I guess I'll make another call to Digital Delay. Any ideas???

Its been a while since I had a Cheetah & 3 speed but I seem to recall the pressure being critical - I don't remember if it was too much or too little but I had the same problem and an air pressure adjustment stopped it. I want to say (if my memory is correct) I was lowering it to attempt to stop it from going 1 to 3 but I needed to crank it up so it made the 1-2 shift more positive and didn't go right thru the gate to 3rd???

quote:

Originally posted by BD104X:
Its been a while since I had a Cheetah & 3 speed but I seem to recall the pressure being critical - I don't remember if it was too much or too little but I had the same problem and an air pressure adjustment stopped it. I want to say (if my memory is correct) I was lowering it to attempt to stop it from going 1 to 3 but I needed to crank it up so it made the 1-2 shift more positive and didn't go right thru the gate to 3rd???

Biondo told me I didn't have enough pressure with my compressed air system but how does it shift fine at 6100 but not at 6500. Plus it shifted fine all of last season but with a different MSD box in it. The Viair system I have only puts out 105 psi.

This message has been edited. Last edited by: Ron Gusack,

I think it was the legendary Sam Biondo himself that helped me fix it at Englishtown. I certainly don't know if that's your problem and my memory could be fuzzy but I think mine would do it inconsistently as well. I was turning the pressure down thinking it would help (CO2 system) but once I turned it up as Sam suggested it never gave me any trouble after that. Sometimes as mechanical stuff ages and wears it doesn't work like it used to. You could also temporarily trigger the shift manually with a pushbutton for a few runs to rule out if its mechanical or electrical. If it goes from 1 to 3 when triggered by the button, then its your shifter and not your RPM switch set up... Just some food for thought.

Thanks Billy, do you by any chance remember what the pressure was when it worked properly? Mine works well when I test it in the garage even when I let the pressure get under 80. Thanks for your input.

No, it was probably 20 years ago but since it was Sam who helped me I would assume whatever the guys at Biondo told you should be accurate.

My CO2 is regulated to 100 psi. The electric over air solenoid is mounted directly on top of the shift cylinder. This uses the least amount of air to shift with and is the fastest. If you have the air solenoid mounted away from the shift cylinder with an airline to the cylinder consider changing it. If mine was regulated to 85 psi it’d work every bit as good imho.

If it shifts correctly at 6200, and then if you raise the shift to 6500 and it fails my bet is you have an electrical problem (wiring or programming).

I too have a th400 w/ Cheetah. I believe the only way it’s going to go from 1 to 3, is to stop at 2 (de-energize) and then be re-energized to 3.

Data acquisition could be helpful in troubleshooting this type of problem.

quote:

Originally posted by markemark:
My CO2 is regulated to 100 psi. The electric over air solenoid is mounted directly on top of the shift cylinder. This uses the least amount of air to shift with and is the fastest. If you have the air solenoid mounted away from the shift cylinder with an airline to the cylinder consider changing it. If mine was regulated to 85 psi it’d work every bit as good imho.

If it shifts correctly at 6200, and then if you raise the shift to 6500 and it fails my bet is you have an electrical problem (wiring or programming).

I too have a th400 w/ Cheetah. I believe the only way it’s going to go from 1 to 3, is to stop at 2 (de-energize) and then be re-energized to 3.

Data acquisition could be helpful in troubleshooting this type of problem.

Thank you for weighing in Mark. This is the set-up I'm using. la-213811363271&CATARGETID=230006180037475786&cadevice=c&jegspromo=thirdparty&gclid=EAIaIQobChMIw4mN86Kr3AIVCBgMCh1WTQFpEAQYAiABEgKW7fD_BwE" target="_blank">https://www.jegs.com/i/Biondo/...pEAQYAiABEgKW7fD_BwE

I haven't done A-B-A's to be sure that changing the shift point isn't a coincident to lead me down the wrong path again because I was going into first round when it first messed up. Fortunately it went 1 to 3 consistently for the rest of the night.

Digital Delay thought it was probably a faulty connection to get the box to go off and on but when I stack the runs, the rpm line on the graph is very consistent. On one run it looks as though it went to 2nd gear for a split second but all other runs it went 1 to 3. This consistency makes me think a faulty wire or terminal is unlikely.

I've tried to get the terminals/wire on the rpm box to show fault on my ohm meter without luck. I've ordered a higher pressure switch from Viair to get the pressure out up. I never had a problem until the 6AL2 went in but it's hard to believe that the MSD is the problem. I have another index race on Saturday but I might be able to get to a tnt tomorrow.

My data logger is a Racepak Sportsman and I use engine rpm to see what's going on. I have a go-pro set up to watch the shifter this week if I remember to take it with me and turn it on LOL.

With a th400 you Do Not want the shifter to go from 1 to 3 without stopping at 2. The transmission will be damaged if you continue this as I was told by ATD and several others when I posted that exact question on YB last year.

That's good to know Mark and I've never heard that before so thanks for sharing.

The plunger that strikes the block on the shifter is about .250 from the block. The install instructions say that it should either be touching or be very close to touching. I called Biondo about that when I first installed it and he told me not to worry about it unless I had problems. I didn't have any problems last year with it so I never called. I also noticed that the plunger has left a witness mark the length of the portion of the block that it strikes. It's not like the plunger hammers the block, it looks like it pushes it although it sounds like it hammers. It's like the duration of the plunger action is too long. I'm thinking about taking it apart and adding some metal to the back of the block to tighten up the gap.

Update on rpm controlled air shifting from 1st to 3rd. Biondo appears to be correct because it hasn't messed up since I put a 120 psi switch in. BUT, it's only been down the track 9 times sine the switch went in. It's been a bad year for rain outs here.