Now that is an awesome example with the particulars you need to know.I have the GV unit with 3:73 gears and 28" tires . 2300 rpm@ 70 MPH. I like it, it's like having a 4speed.
@DesertRat , do you know the OD’s final gear ratio?
Now that is an awesome example with the particulars you need to know.I have the GV unit with 3:73 gears and 28" tires . 2300 rpm@ 70 MPH. I like it, it's like having a 4speed.
Yes
So, third time! What is the OD ratio? What is the tire size. Please don’t list “Nitto 325....” give me the actual tire diameter.
Yes the .78 is the number. Some folks don't think its enough but for me it worked out in my 67 notch. The one thing I did to mitigate the converter slip is go with a lock-up converter but after driving it a year I had the transmission shop remove the lock-up feature. The car is much more driver friendly with a little converter slip and it only cost me 100 rpm. I now cruise at 70 MPH @ 2400 RPM. My motor is real short on torque, builder mistake on me:-( But for a 408 it will work fine.Now that is an awesome example with the particulars you need to know.
@DesertRat , do you know the OD’s final gear ratio?
I can reason out and mathematically prove how a GV is an advantage. In the real world, I have zero experience, in my head, I think about it all and I can not find a single reason to purchase or use one. IMO, it is not cost effective. My wallet is to thin to play with one. I myself would rather use a factory 4spd auto or a manual trans that has a OD gear, be it a A-833 or Tremac variant.
BUT! This is just me.
Did YOU make a big MISTAKE?
IMO, I don’t think so since you thought about it and decided to make the leap. Your reasoning was sound in your head, go for it. And enjoy it! I called out to AJ/FormS because he has one and loves it.
AJ is a good man and a solid dude that will help you out.
He gets my stamp of approval and a big thumbs up.
I'm going on what some people here have reported and the fact that the GV doesn't have "that good" of an OD ratio on paper. There have been a number of people on here through the years disappointed with them. For 3K dollars, you ought not to have to modify the floor, either. JMO
Figure out where peak torque is on your car (I.e. dyno).
Figure out how fast you want to run on the freeway.
Pick the deepest rear gear as close as you can to make the two above coincide in top gear. You'll need your tire size and calculators for this are all over the net.
It really is that simple.
Maybe someone else covered it, I ain't reading all these posts.
Example. Peak torque 2500 RPM.
Freeway speed 80mph (you's in Montana an alla that).
From their website:
Overdrive is 0.78.
So by the chart, the gear in red will behave like the gear in black.
Dodge 3-Speed Auto - Gearvendors
So with this calculator, 3.23 is your bingo (I just picked a tire size, Your mileage will, literally, vary)
Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio
Switch to 3.55's, and you're cruising at 2800.
Compare this to a true six speed with double-over, and you'll see why people don't like the GV unit.
Have you given thought on how to fit those 315s into the Duster tubs?1974 duster
Blueprint 408 stroker (465hp,550ftlb)
Dana 60. will be doing more street driving that track. Tires will be cobra Gt 295’s, but will also have a set of 315 nitto Nt05’s.
I'm not understanding this comment; so I'll take a stab at it' . Sensitivity at tip-in is always one of:Want it to have great acceleration to keep up with modern sports cars on the street, but not be too geared up that the pedal is so sensitive it becomes not fun to drive
Oh yeah, yur on the right track.haha I hope I didn’t make a stupid purchase. Makes sense to me to split 2nd and 3rd gear, have more range in the power band, higher gear for more acceleration and the OD to drop rpm ~600 on the highway.
engine is blueprint engines 408 stroker with hydraulic cams matched to there built 727.
Appreciate that! Would like to get this build right the first time without taking the Dana 60 out again to change gears haha..
yeah originally I was going to do a 4L80e built trans by Jake’s performance m, but didn’t want to cut up my tunnel that bad and Blueprint Warrenty covered there engine and 727 trans. When I put my nitto 325 tires in I’d like to have a high gear and get those tires to hook for some serious acceleration. so guess I’m stuck with deciding 3:55, 3:73 or 4:10 gears.
[/QUOTE]Tires: 295 60r15 cobra & 325 nt555gii; should I just ditch the OD and go 3:23 gears?
I think those units are stupid. Like a passing fad.
[/QUOTE]Ok so I put most of your comments from page 1 into one place, so I don't get confused by what others have said. And then I will comment in blue.Keep in mind that I'm just a guy with a calculator, that happens to have a GVod.
I'm gonna post it out as I go, on account of my computer likes to lock up and loses the draft when it does.
Have you given thought on how to fit those 315s into the Duster tubs?
I'm not understanding this comment; so I'll take a stab at it' . Sensitivity at tip-in is always one of:
1) too much low-rpm timing, or
2) primaries that are too big, or
3) too small a rear gear, or
4) a spastic right foot, or
5) some combination of the above.
Oh yeah, yur on the right track.
But I see two things in your thinking that I can't agree with;
1) You have a 408, and
2) on street tires, that
3) in a Duster weighs practically nothing to a 408
Ok so with a 408, a 727, a modest stall, on 295 Cobras, in a duster ..... is a recipe for tirespin......... no matter what rear gear you run. And there is NO CHANCE to split second and third. I mean you can but there is NO POINT IN A STREETER
Lemme explain
Your 727ratios are 2.45-1.45-1.00 adding the .78 GV ratios in Red I get
2.45-1.91-1.45-1.13-1.00-.78od, your splits are
.78- .76-.78-.88-.78
So if you are in second-over and shifting to Third your Rs will drop to 88%, which, from 5500 is to 4840, is a drop of 660 rpm, which sounds good but here's the deal; with street 295s and 3.23s, that comes at 85 mph, and in all likelihood your tires will still be spinning. Soooooooooooooo what advantage is there to having the GVod in this instance? Answer; I hope you are somewhere that the coppers ain't. Remember what Rusty said? So that's strike one.
Strike two for splitting is;.
Between First and Second the splits are very nice and tight, a sucked out 318 would love it, for all the reasons you would think.
But will your 408 love it? If your tires are spinning in first on the split, then no. If your 408 spins the tires in second gear then no. I have had those Cobras behind my 367 and she spins them to long past 60
If your 408 cannot roast 295 street Cobras to 60 mph. it is sick. So then, what advantage is the GVod in this instance? For splitting the big 408, IMO, nothing; certainly not anywhere near worth the buy-in.So that's strike Two.
Strike three is this; The GVod cannot be backshifted under power. So when going from First-over or Second-over to the next non-over gear the power has to be interrupted while the unit out-shifts.
End of the bad stuff.
Here comes the good stuff
With 3.23s your trip to 65mph cruising speed could end at 3000/zeroslip3300 under power in Second over. Dropping into Third-over at 2060@zero slip. Do the math. That is a drop of 38% making the OD EFFECTIVE ratio.62.
OOPs the grandkids just showed up
passing fad going on 40 years?
Keep in mind that I'm just a guy with a calculator, that happens to have a GVod.
Not on the street, well maybe, but you can't measure it lol. The GVod needs a power interrupt on the out shift. What you gain in, the more average power delivered, you will lose on the interrupt. Furthermore on the outshift, the GV does not shift instantly when you hit the button. So you have to anticipate it.I would really like to maximize the power of my engine, I know traction will be a big issue but if I could get the tires to hook, wouldn’t a GV and 3:73 gears be much quicker?
Some people say a certain 2000 year story is a passing fad. Course, that ain't me.
....but mods are what hot rodding is all about.
Thanks guys , as always; just trying to help.Sounds to me like you're exactly the person he needs to talk to in this case.
IMOThat’s what it’s about for me. Sure, I’d like to not have to do floor mods, but if I need to for the result I want to fit with what I’ve got, I’ll do it.
Thanks guys , as always; just trying to help.
IMO
a 4-speed automatic with a hi-stall and loc-up. is a better idea than a GVod behind a Mopar automatic.
Yur 4-speed auto will act like a 5.5 speed.
You wanna see how?
Ok I'll give you the short version;
The Hi-stall will give you an extra bottom gear, and the locv-up will give yo a half a gear for cruising, so 4 +1 +.5=5.5
....but mods are what hot rodding is all about.
IMO
a 4-speed automatic with a hi-stall and loc-up. is a better idea than a GVod behind a Mopar automatic.
Yur 4-speed auto will act like a 5.5 speed.
You wanna see how?
Ok I'll give you the short version;
The Hi-stall will give you an extra bottom gear, and the loc-up will give you a half a gear for cruising, so 4 +1 +.5=5.5
But IMO, the A500 has ratios that are way too far apart, and the A518 are still too far apart.
All the gears are in the same case, so you don't have to deal with the add-on GVod. And you can never bust the GVod by backing up with it still engaged..... Like I did. If I was not a stick-man, I would open up the tunnel in a heart beat.
The A500 has a starter of 2.74 and finishes at .69 for a range of 2.74/.69=3.97, which,IMO, is too broad, and individually, the gears are a lil too far apart for performance, for a small block, but not for a stroker.
The A518 is 2.45/.69=3.55 still too far apart for a 4 speed. But the Chevy's are not much better, most are actually worse. But they are more compact and fit better in the tunnel with less mods.
Depending on your combo you might have a lot to play with. If you have a stroker, they have a lot of torque and don't need a 3.73 or 3.91+ to make it work. With a modest gear (like a 3.23) and a lot of torque, you can burn tires at will and still cruise at 65 on the highway at around 2500 rom or so. Like the best of both worlds without a overdrive.That’s what it’s about for me. Sure, I’d like to not have to do floornmods
If I didn’t have the Pushbutton automatic, I would absolutely go for a different trans. I just think it’s too cool of a feature to get rid of.
On the electric shifts you could, but that .69 is brutal, the shifts are better thru the main box. The A518 ratios areThat said, how's come I can't split gears with the OD unit on a 518?
Some people say a certain 2000 year story is a passing fad. Course, that ain't me.
But yeah, I'm just giving my opinion and reporting on things I've seen people who've had them say on this forum. Seen some pretty disappointed in the OD ratio and the floor mods....but mods are what hot rodding is all about. If you're gonna be a cry baby about that, there's always tiddly winks.