Just picked up a used Gryphon

[Medic150]

Originally Posted by JackandJanet

I suspect what you felt as surging was the engine hitting the rev limiter between the 2-3 upshift. In a Wide Open Throttle (WOT) shift situation, the shift is commanded at a specific RPM, which you can set in the Custom Options Menu. I would not set this shift point above 5100. (Actually, I like 4975, since the torque and horsepower are generally dropping above 5000.) Now that i look back, that is exactly what happened.. I had never hit my rev limiter on this truck before, I guess I hit since I was trying out the 0-60 function.

Now, as the shift is commanded, the transmission clutch is applied, allowing the engine to freewheel for a short period (until the clutch is released and the shift completes). The freewheeling engine RPM rapidly increases and if it hits the rev limit, spark and fuel is cut to prevent damage. The RPM drops and then the whole cycle repeats until you come off the gas a bit.

If you make sure the rev limit is at least 400 above the highest WOT shift point, this problem will generally not happen. I have my rev limit set at 5500 in the Custom Options Menu. Don't go much above this point either, because the Torque Converter (TC) starts to balloon above 5400 RPM. I have to learn how to do this..

By the way, don't set the 3-4 upshift too high. It's actually hard to get a genuine WOT 3-4 upshift unless you're on a racetrack. My shifts are around 4975, 4975, and 4400.

Are these your rev limiter settings for 1st 2nd and 3rd gears ??

[Longshot270]

The rev limiter is a maximum that the PCM does not let the engine exceed regardless of gear. The individual rpms Jack listed are WOT shift points. This is where the computer tells the machinery to change which gear is being used, because of delays and such the actual shift can occur later and at a higher rpm. The rev limiter comes into play here because the shift points, in order to improve performance, are set as high as they can practically be. If the engine does not shift into the higher gear soon enough it can actually rev high enough to get caught by the rev limiter and cause trouble with the shift. That is why the general recommended gap between the shift points and rev limiter is about 400 rpm. The 400 rpm gap gives a better buffer for shifts that dont work perfectly.

[Jackpine]

Thanks, Longshot - exactly correct. But I'm not certain Medic150 understands. The Rev Limit (RPM Limit?) is a SINGLE value that is one of the menu choices in the Custom Options Menu. I think it MAY default to around 5300, which would be too low for a WOT upshift from 2-3 set at 5000.

Setting these values is pretty easy, but read through this: http://forum.gopowerhungry.com/faqs-...ions-menu.html (making sure you understand it) before you do. You WILL have to manually set your Tire Size (TS) and possibly your Gear Ratio (GR) if you open that menu.

- Jack