Winding out the RPM

[kanui]

I have a 6.5 with manual transmission. I was wondering how far you can wind these motors out. There is no tach in this truck. First time I ever owned a manual trans with no engine tach. Can you wind the rpm all the way out then shift or do I have to keep it under a certain rpm. I don't want to tear it up but I don't want to lug it around if I don't have to.

[6.5 Detroit Diesel]

if you can, find a junkyard and locate a dash panel that has the tach on it. it is as simply as removing the old panel and plugging in the new one.

these engines will howl when you hit the top end. i have hit 4K in mine, but most guys here like to treat their engines nicer and will keep them under 3K.

best thing would be to get that tach. my 93 didn't have a tach, but i learned real quick from listening to it when i was redlining.

i learned this after shifting from 5th to 4th at 130KMH and floating a pushrod.

[DmaxMaverick]

The mechanical injection pumps are governed internally. If the pump is healthy, it should limit RPM's under power at 3500-3600. Unless you have other issues with the engine, it can run at this speed all day harmlessly. A tach is handy, especially for hand-shakers, but not necessarily required. Shift at whatever engine speed seems most effective and comfortable for you.

Compression braking (down shifting), on the other hand, is controlled by the driver. You don't want to wind them past about 4500 RPM's. You should have no problem knowing long before you get it that high, even without a tach. You shouldn't be able to float the valve train within any reasonable use (including high speed compression braking), but if you do, you'll have other serious issues to deal with (broken pistons, bent valves, etc.). It shouldn't be an issue until you are well north of 5K RPM's.

[6.5 Detroit Diesel]

not sure what i hit when i downshifted like that, but it was almost five years ago. i pulled of the valve cover, used pliers to pick up the push rod, put it back in, replaced some guides, and drove that truck for four more years.