8.25 Swapping gears to Abody Unit

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I have a 65, or 66 B body rear I could swap a 3:91 open punkin in. Not sure what the final drive ratio would be. with the 833OD would be. It has 3:23' 7.25 now.

I need to clarify my mess. I want to get rid of my 3:23 7 1/4" rear. They have worked good as in 22mpg @ 82mph with the original 3 speed.

I have a 65, or 66 B body rear in the shop. I have a complete chunk that could go in it. It's an open 3:91.

I was wondering about the 3:55's with the sure grip 8 1/4" in the shorty van. Pulling out the guts and swapping them into an A body 8 1/4"
 
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It's a little hard to decipher what you want to put into what.
I'm gonna talk about gearing only.

>As for installing the 8.25 van guts into an 8.25 A-body rear, I believe that is doable, so long as neither of them is a 2.45 or less ratio. Ima thinking the van will have longer axles and IDK anything about the spline-count. But guts for guts should work.
> Notta chance would I install 3.23s behind an A833od and a slanty, in a van; as Second gear will be a total downer.. and it is highly unlikely that fuel economy will be any better than with 3.91s. because , Cruize rpm with 3.23s (1850) is too low for to generate adequate timing; and with 3.91s (2250) is not too high, and still hard to generate enough timing.
> 3.91s and the overdrive are a good combo, for just about anything.
> A hi torque V8 will pull the od with 3.23s, but it better have a 318-sized cam in it, or adequate cylinder pressure, or I guess if you're not in a hurry; but Second gear is still a problem........ because 1.67 x 3.23=5.39, which is a good third gear, but a bad Second, cuz you just get into it at too low an rpm, unless you wind it up in First. A low torque engine is gonna struggle.

Here's what I mean;
Say you installed that 3.23 behind the od-box and the slanty in a 4000 pound Van.
The road gears are;
9.98-5.39-3.23-2.29 with splits of .65-.60-.71
So lets say you roll first out to 3000rpm. When it drops into Second, the Rs will fall to
.54 x 3000=1620@24mph, Yur engine better have some torque down there to accelerate in the next gear . She might, but at what throttle setting?
So then, you run Second up to 3000, and on the shift, the Rs fall to 1800@45mph. Now you have a long hard pull to hit 65 @ 2600, then into od and down to 1860.
This is not gonna happen in a hurry, cuz the slanty is always working hard from a minimum of say 1620, to 3000 or less.
More than likely you will need to get her up to 4000 in First to drop into Second at 2160=32mph, to find enough power, to make this go reasonably fast enough.
Now, lets talk about that 2160@32 mph in traffic ...... ok lets not cuz you know that slanty is gonna suck!
So then, my best advice is do not try this at home.
lol
 
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i'm about to drop 3.91's and a OD into my 65, the gear calcs work out pretty decent for what it is.

avoid the 3.23 + OD, that's gonna be a bummer everywhere except 1st gear.

if you're talking about a swap-a-roo of the 3.90's onto the 3.23 SG carrier, yes it can be done.
(caveat as long as the spline counts are the same-- which they should be)
 
There are two 8-1/4’s. Off the top of my head I don’t remember what year the change happened. Later model won’t work with early.
 
go-fish said:
There are two 8-1/4’s. Off the top of my head I don’t remember what year the change happened. Later model won’t work with early.
Click to expand...
1996 1/2 changed the spline count on the carrier

to my knowledge the gears remained the same.
 
Rug_Trucker said:
I have a 65, or 66 B body rear I could swap a 3:91 open punkin in. Not sure what the final drive ratio would be. with the 833OD would be. It has 3:23' 7.25 now.

I need to clarify my mess. I want to get rid of my 3:23 7 1/4" rear. They have worked good as in 22mpg @ 82mph with the original 3 speed.

I have a 65, or 66 B body rear in the shop. I have a complete chunk that could go in it. It's an open 3:91.

I was wondering about the 3:55's with the sure grip 8 1/4" in the shorty van. Pulling out the guts and swapping them into an A body 8 1/4"
Click to expand...
8 1/4 gears come out the back side like the 7 1/4. 8 3/4 the whole 3rd member comes out the front. Will not interchange. I don't believe the 8 1/4 was in 65 or 66
 
You say the 3.23s work well in your Duster with the 198slanty and the 3-speed.
My guess is that by 3speed, you mean the A230.
That trans should have ratios of
3.08-1.70-1.00 but could have; 2.55-1.49-1.00. Let's say it was the 3.08
the roadgears would be
9.95-5.49-3.23; So this is the standard against which to measure any improvement.
The overdrive has ratios of
3.09-1.67-1.00-.71od Roadgears with the current 3.23s would be;
9.98-5.39-3.23-2.29 , about same as with the A230, but with an extremely high 2.29 cruiser. At 82mph, your cruise rpm would be around 2340, versus 3300 with the A230
IDK if your 198 can pull 82mph at 2340 rpm.
But, I get the sense that you want to ditch the 3.23s because now you can, even tho, "they work good."
Lets say you target a cruise rpm half way between 3300 and 2340, = ~2800.. This would take 3.91s and, the new roadgears would be;
12.08-6.53-3.91-2.76, and 82=2835/65=2250
and; 35mph=2850 in Second gear, with these 3.91s; versus 2390 with the A230/3.23s.
So you have an improvement in Second gear, of 460rpm or 19%; that will put some spunk into the ol' 198. The First gear, 12.08, will take off 21% better than 9.98
So this is a winning combination in every way. Well except for with a starter gear of 12.08, from a redlight, you'll barely make it across the intersection, before the 198 is asking for a shift........... 20 mph is already 3000. but a shift into Second will get you 1620, which is a bit of a bummer, but hey, you're only going 20mph with a lightweight Duster, so, the 198 isn't exactly "lugging". 4000 will get you to 27mph, and to 2160 in Second. No matter how you look at it, this is still better than with the A230/3.23s.
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On a sidenote; I have run this combo(A833od and 3.91s) in my 68 Barracuda with a 360 engine/223 cam and it was awesome! But you know, I have also run that combo, geared at 65=1600 lol, which IMO, was the epitome of that combo to generate fabulous fuel economy.
In the end, I ditched both the trans and the 3.91s, for the Commando/3.55s, and a GVod.
Which your combo is begging for, but I understand economics. Just FYI, the Commando/GVod with 3.23s would get you Roadgears of
9.98-6.20-4.52-3.23-2.52, and 65=2040/82=2570 yummmmmmm.
35=2700 in Second, more Yummmmmmmm
and the rpm drop between First and Second is to 62% so
if you run First to 3000, the Rs drop to only 1860, not 1620.
But I know, the GVod is not cheap.
Still, selling your A230, and your A833od, and your other junk, and NOT buying 3.91s or 3.55s etcetera, will go a long way towards what I know for sure, would be your final combo.
Having said that;
Your 198 is actually begging for an AX15 ratios of
3.83-2.33-1.44-1.00-.79od, splits of .61-.62-.69-.79
This combo has been installed by a few guys who love it; and it looks like the bugs of the install have been worked out. This combo could work out well with the 3.23s, with Roadgears of
12.37-7.52-4.65-3.23-2.55; 65= 2065/82=2600 and
35=3000 in Second/1850 in Third.
Just FYI.
 
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