High Rpm....low speeds

Hey just a suggestion but if you are at 1500 RPMs at 65 miles an hour and you were at 1200 / 1300 it's possible your speedometer is not reading right. Or your tach.

Or...

I'm sorry I can't go back through this whole thread but somewhere you listed the transmission model was there a letter at the end of that? Like RTX 14610 C?

That last letter indicates the spread between the ratios of the gears.

I don't know how the newer Transmissions are set up but maybe for a truck that's geared that incredibly High they have the lower gears very low and close together and the upper gears spread out.

You have to look at the ID tag and then Google what the ratio steps are for that.

And not to be making the waters any more muddy, but maybe you have an engine problem if your truck doesn't feel like it's pulling right...

 

@trucky909 I went and looked in your other thread and you mentioned your DD15 has been deleted. Did this by chance start after the delete??

 

No point reasoning with a guy that quotes himself telling himself what others have.

I like would question if the glazed flywheel was resurfaced.

 

Right now the easiest thing to do would be to write down your speed in each gear at 1500 rpm. Then go to a gear calculator and punch in your info and put in the ratio for each gear and see how it compares to your actual speed at 1500.

Are your rpm’s still going up faster relative to road speed empty compared to loaded like you stated before after the new clutch?

 

Transmission Ratio RPM Calculator | Spicer Parts

There's the link..
This is my rpm, road speed for all gears at 1800rpm. Speed in box, ratio for each lever position above boxes..
RTX 12609B. 4.10 rear, 11r22.5 tires
Notice even at redline, about a 500rpm drop ~1800-1300rpm
Low-1 gains 2.9mph
1-2 gains 3mph
2-3 gains ~4mph
3-4 gains 5mph
4-5 gains 8mph
5-6 gains 11mph
6-7 gains 15mph
7-8 gains 20mph


Did you ever verify the actual trans model you have.? I think you said FR 15210 or something.? Check the model # on the case to make sure it matches the model # in the glove box..

On my picture, in black ink shows what the ratio is for the Low hole, but in high range. Effectively, it's like a 3.5 gear between 3 & 4 low range. So if someone stole your 10speed, put a 9 in there like mine, when you "think" you're shifting from 5 low to 6 high, you might really be shifting 4 low to Low high, or like a 3.5 gear effectively gaining no speed till you shift to 7th. Really the 5th position if it's a 9 speed.. Just a thought.. Here's the pattern to help visualize what I'm trying to convey..