Shifting problems?

["Mad Max"]

Fellas - I'm reading these mph numbers verses od engagement, and I have to ask some stuff - There must be a whole lot of pump adjustments I can make, because my rig will not go faster than about maybe 60 mph in 3rd at max pedal (about 2400 rpm). I haven't tweaked the pump to rev higher, but the overdrive engages nice and firm around 35 mph and holds firm unless I mash the pedal, then it will disengage, crank up through 3rd, and shift around 50-55 mph. So, here's a couple questions:

What max rpm are y'all turning on daily driver bombed engines, and what is your highway gas mileage unloaded at 70 mph?

I'm curious if I turn up the pump if I will kill or encrease my mileage? I'm mostly doing unloaded drives back and forth to work, but when pulling the toys I don't really care about mileage (at least that is the rule of thumb with my big block rig)



I think I'm just not used to bombing tricks yet, and the results of the modifications to the pump. Gotta read up on all that stuff, cause I have got to be missing some simple tricks. No one around here speaks 'bomb' very well, especially on the pump.

- Sam

 

[BushWakr - RIP]

Hi Sam,



My max governed (physically set by screw) RPM is about 3500 WOT. It will "flare" higher with a 'no load test'.

If you alter your pump settings you can expect to see some mileage decrease at some point.

In my case prior to the last set of tweaks I was running about 18-18. 5 mpg around town stop and go.

Highway was a bit better.



Now, with the current settings I'd estimate around town is 16mpg. I have not yet done a full tank to full tank calculation yet so I may be off a tad.





Bob.

 

[Philip]

Sam



The rear gears have a roll in how fast you can go in 3rd. You say your only good for 60mph flat out in 3rd. That sounds like a set of 3:54's. My truck has 3:08 gears. I hit 89 in 3rd. I do not have a tach so I do not know the rpm.

what is your highway gas mileage unloaded at 70 mph?

I can't say at that speed. I have never run it long enough to get a mpg figure. At 60 mph I get 20 mpg. At 80 I get 17 mpg.

 

[Greenleaf]

Overdrive Shifts, RPM's , MPG

To begin, I don't know my rpm's, haven't got the tool. Have yet to dial in my pump; timing,speed,and full fuel. I will mention, my speedo is off a bit. maybe six or seven mph. Don't know why. That's another subject. Perhaps tire size???

I have 3. 54 gears. And... ... I don't know my mpg, never bothered to check. Will say that the gauge is off a tad. Drops rather quickly from full to half then moves slower. Noticed that a fill-up at half of a tank is 12 gallons.

The transmission won't grab OD when the pedal is glued to the fire wall,while pulling a long steep hill. I believe this to be normal[?]. It will shift if I back out a bit or crest the grade, which brings up the rpm's. I'd rather it shift because she really comes to life when it grabs OD. I'm guessing that the mods I'll be doing will change things somewhat. By experimenting with the throttle position sensor I can change the shift points somewhat.

Sometimes I think I pick and worry to much about the little things however there are many worse things I could be doing with my time.

Hope this generates some positive ideas/discussions. ILMD [ilikemydodge] Have a good one!!!

scott

 

["Mad Max"]

That sounds about right - My 3. 54's are just right for what I want to do - great unloaded, and fine when loaded - can do 70 mph no sweat loaded, in o/d. I am putting a set of 2. 76's in my 1970 Challenger I'm restoring now - it has a roller cam 88 '360 built specifically for efficiency (good cylinder pressure and exhaust scavenging) and low end torque, 5-speed manual with o/d, and has a 3. 08 transmission first gear ratio - should be the perfect highway cruiser, should get around 25 mpg, and should come out of the hole like it has a set of 3. 55's. Can't wait to get it rolling - sometime around October. Taking the engine to a dyno to break it in separately this summer.

Anyway, sounds like my rig is right on the marks 'as is'. After some pump tweaks it should have more speed, though I really don't need it. I'm planning a swap to a NV4500 with a GearVendors O/D mated to the back of it - Quad 4x4 is going to do the mate and then ship it all as a complete unit. Not cheap, but I like manuals, and I want 1700 rpm cruising at 75 mph getting 24 mpg. The whole conversion is going to be a tech writers dream - I'll have to do a TDR project truck conversion thing - that would be a lot of fun to document.

Thanks fellas -

- Sam