Cascade Crew

Danked · Posted: Mon Sep 04, 2006 3:25 pm Post subject: How do i know about my rpms

how do i know it hit 10k rpms? well, 40mph is 6k rpms or so in 1st, 40 divided by 6 is 6.7, so 30 divided by 6 is 5, 6k rpms + 5 (for 5k rpms at 30mph) is 11, so im guessing it was at about 11k rpms, even though the tach did go up to about 8k, just means that the tach is only capable of going up to 8. therefore im GUESSING i was at 11k rpms or so.

aaron_sK · Posted: Mon Sep 04, 2006 4:05 pm Post subject:

Math.... yay! Evil or Very Mad

Okay then, some assumptions on my part before I start:

1) You run a stock gear ratio of 3.23
2) You have a stock TH-700R4 (3.06/1.63/1.00/0.69)
3) You have a stock 12" stall converter
4) You run 26" stock tires
5) Your tach is probably wrong

Punch all those fun numbers into a calculator, and you get 8941.037538461538

Now if you had a 5-speed that would probably be close to right. However since you have an automatic you have to remember that you do have a stall converter in between your tranny and flywheel, and like Tony already said, usually a tranny will not shift down or into reverse immediatly.

Danked · Posted: Mon Sep 04, 2006 5:09 pm Post subject:

i dont know the diameter of my tires, my rears are 245 50 16's, and it didnt shift immediately, about the time as i was saying "i knew it wouldnt s...." *bam*

chevymad · Posted: Mon Sep 04, 2006 5:39 pm Post subject:

Danked, yes you overrevved it, but there are too many things that happened to know what exactly you revved it to.

As several have said your tach most likely is off, basically all stock tach's are off, you just don't know by how much.

Tony was trying to tell you about the the tranny not shifting down, that is sort of right. Without a shift kit the trans will shift up out of a gear when a certain # of rev's are reached. With most kits you can hold any gear to any rpm. So by shifting down your tranny did shift down, until the governor weights are spun up to a certain speed, then it will shift up again. In your case probably very quickly. So you won't be able to use math to figure rpm's because you were in a sort of limbo area, in and out of 2 different gears.

Also as has been said you have a torque convertor. If it isnt in lock-up mode then it isnt a positive connection between the motor and trans. Slippage is allowed in either direction. So even by going into a lower gear the convertor will slip and the mathmatical rpm won't be reached. Used to be the thing for kids to do reverse drops with their rigs. You'd be heading down the road 60mph and drop the trans in reverse. It would light the tires up, but no the engine did not start turning backwards! lol In fact due to the convertor usually the engine continued to run.

That brings up another possibility. Tire slippage.

As you see there are all kinds of things you just can't figure out to come out with an exact # of rpms. Besides this isnt what blue89 was talking about anyway. He wanted to find the limiting rev factor in his engine, by comparing it to what a stock engine will rev to. BTW I don't recommend you try free revving your engine to find out either. Unless you are ready to put in another. When you free rev an engine there is nothing cushioning the parts, keeping them from flying apart. When there is a load on the engine the piston is being pushed down which pushes the rod down, which pushes the bearing against the crank etc. Free rev's this is all basically floating. If there is any weak point in your setup it can come apart. It's much easier to spin a bearing because it isnt being pushed into the rod. You may also float the valves, which means you could hit the valves with your pistons and break/bend them. Just a warning.

Danked · Posted: Mon Sep 04, 2006 5:49 pm Post subject:

i understand what your saying, i believe he was just asking how high our v6's could possibly rev until it would stop itself. i was just explaining that i may have hit 11k rpms, because it did actually shift into 1st. you guys are saying its impossible, but it did. i dont know if my tranny has a shift kit, but i was racing a honda down the freeway one night, had the gas to the floor of course, and it usually shifts at 6k rpms, to the next gear, however, it was in 2nd, my shifter was in OD and it was going into the red line. when it reached 7k rpms, i let off the gas in order not to blow the engine. not saying that my tach is right in fact, just saying what my tach was saying it was at. in conclusion, i was stating that if my engine really was that night in fact at 7k rpms and still accelerating, why couldnt it drop into 1st at 70mph.

aaron_sK · Posted: Mon Sep 04, 2006 5:58 pm Post subject:

Shifts at 6K means your tach is way off, or the governor is screwed up. I'd bet good money on the first.

BTW, did you win?

Xophertony · Posted: Mon Sep 04, 2006 6:21 pm Post subject:

wow! you must have one hell of a tranny dank. i would never have atempted that with my 700r4, it would have thrown the flexpate through my ankles and thrown 3rd gear up my ass. Shocked

i am sorry to have doubted your claim, clearly you know what you are talking about here. Surprised

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Quasi-Traction · Posted: Mon Sep 04, 2006 6:30 pm Post subject:

chevymad · Posted: Mon Sep 04, 2006 6:44 pm Post subject:

OK, this threads gotten away from us again. Danked I hope your question is answered. You'll have a hard time making anybody beleive 11k, even if you did. Please do not start another thread on this subject or I'll have to lock it as well.