• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

"best" RWD volvo?

the poi

the poi

Has been
Joined
Jan 5, 2003
Location
Pasadena, CA
im primarily concerned with the interior and teh suspension, as I'm planning a ford v8 swap. cept the 940, although it has better suspension options, has a 700 series interior. the later 960's and the s90 have a better interior, but the indpeendent rear susp. makes it "impossible" to upgrade. my first question is why is it so hard to get better shocks on the IRS of these cars? and, if all the shocks and springs were adjusted to the most aggressive available, would the 960/s90 be responsive enough to handle the power of a v8?
 
mmm, i dunno about the part "the diffs can take the power".. I've worked my way through a couple this year.

If I were to do a v8 swap, I would find the newest non-irs 700 series car(preferably a turbo car with a blown motor.. for whatever reason people do less maintenence on them around here than the na cars), and whilst doing the swap, put in a ford 9 inch.. you can find those on car-parts for 150 bucks, and aftermarket stuff for them is plentiful and cheap, and they're supposedly damn tough.
 
thanks for the fast help.

first question, more of just general interest: why is it so hard to get shocks that work with the IRS? i mean, why are only a sepcific model of nivomats compatible with it? and also, what are your estimates for the best shocks, the springs, and a custom bar?

and linux, how much custom work im i looking at with a ford differential? i intend on doing as much work as possible by myself, and im gonna have to buy some welding equipment anyway to get through some other things anyway. or, will a new diff require some expertise that im never gonna have?
 
I dunno, I've looked into replacing mine with a ford unit, but no one's nice enough to gimme one so i can size things up ;)
you'd probably need to get a driveline shop to weld a new end on the driveshaft, past that, your guess would be as good as mine to what would have to be done... it can't be that hard, unless the rear end on a ford is wider/narrower than a volvo rearend
 
kenny,
You realize that the strength of these diffs is largely dependent on ratio right?

Lemme guess, at least one of those diffs was shorter than 3.73?
If you put 4.10's in or something you'l eat them constantly. The carrier's just too small.

For a V8 conversion you'd probably be looking at a 3.31 or 3.56 which should be fine. If you chekc out that twin turbo 6 cylinder 242 in the off topic section, you'll notice he's got 460hp and is running a 1031.
You'll also notice that it's a 3.15. ;)
 
Just a thought here, The highest powered rear drive volvos were the "90-91 780s w/B230FTI Turbo+ 3rd generation with IRS", then the advent of the front wheel turbos maxed the 780s by about 20 hp..... 780s are heavy so one must conclude some lower powered turbos would be faster all around....

Just my $ .02
 
CaptainBondo said:
You realize that the strength of these diffs is largely dependent on ratio right?
Click to expand...

Sorry, I've got to take you to task on that one. Differential strength hinges on one deciding factor, ring gear size.

"Ratio matters not young padawan, only ring gear yes.." - Yoda

This is the reason that the Ford 9inch is so strong, is that is possesses the larges (9") ring gear. The GM 12 bolt was a 8.75 ring. This is why the 1031 is stronger than the 1030 DANA rear.

Check out the article about beefing up a 7.625 rear at http://www.thirdgen.org/newdesign/tech/beefinguprear.shtml. A lot of the info there can be applied to a Volvo rear end.
 
Ok, Nomex boxing gloves are on. :roll:

You're only including half of the equation. The greater the ratio, the more torque the ring gear's teeth see. It makes sense.
It's a torque multiplier, and it is the LEVERAGE, ie the ratio between the ring and pinion that causes strain and breaks teeth.
Same reason transmissions last longer with short diffs, the inertia the gearbox "sees" is less because the diff is exerting a greater mechanical advantage. So the drivetrain shock is proportionally transferred to the guts of the diff.


I'm still waiting to hear what ratio's those were he broke. If at least one was not greater than 3.73 I'll eat my nomex socks. :nomex: :nomex:
 
CaptainBondo said:
Ok, Nomex boxing gloves are on. :roll:

You're only including half of the equation. The greater the ratio, the more torque the ring gear's teeth see. It makes sense.
It's a torque multiplier, and it is the LEVERAGE, ie the ratio between the ring and pinion that causes strain and breaks teeth.
Same reason transmissions last longer with short diffs, the inertia the gearbox "sees" is less because the diff is exerting a greater mechanical advantage. So the drivetrain shock is proportionally transferred to the guts of the diff.


I'm still waiting to hear what ratio's those were he broke. If at least one was not greater than 3.73 I'll eat my nomex socks. :nomex: :nomex:
Click to expand...

LOL I'm not flaming.. just my .02 (Swahili). If the torque multiplication was such a factor, then 4.10's would break every pinion and ring out there, regardless of size. Enough HP and put some sticky enough tires on a car (thirdgen F-bodies camaros & firebirds are notorious for this) and they'll snap 7.625" 3.23 rears all day long. Going up to 4.10s won't help, but its the inherent lack of strength in a small ring that kills them.
 
weak ring gear or not, it'll last longer when subjected to less torque.
They break becuase of a weak ring gear, but what i'm saying is that said ring gear will last longer in a taller diff.

Short 9" don't break because they are strong. Taller ones would be stronger yet, but it's generally redundant.
 
8)

impssr3.jpg


I maybe have built one or two 650hp capable rearends that were show quality to boot. But I'm not here to argue, just to say this is what I know, right or wrong. Let the gentleman take the advice at the value he paid for it.
 
quote]LOL I'm not flaming.. just my .02 (Swahili). If the torque multiplication was such a factor, then 4.10's would break every pinion and ring out there, regardless of size. Enough HP and put some sticky enough tires on a car (thirdgen F-bodies camaros & firebirds are notorious for this) and they'll snap 7.625" 3.23 rears all day long. Going up to 4.10s won't help, but its the inherent lack of strength in a small ring that kills them.[/quote]

Third Gen F-bodies do indeed eat those rears, the 9 bolt BW w/3.27:1 ratio however seems to hold up better only on my 2nd one..........
 
Ahem, back on the topic, I would have to reccomend a 780 as the RWD volvo of choice simply because it is so damn cool.

Sure, the saddle hide leather heated power seats are a little heavier than the manual cloth ones in the 740. Sure the roof structure is a little heavier. Sure there is an extra hundred lbs of sound insulation, and another 50 of (real) wood trim inside. That clear glass sunroof also adds some weight. And you do have to put the manual transmission in yourself, and score an '87 if you want a solid axle (one of the rarest years) .....

But it's worth it. It should be mentioned that I may have a biased opinion. :D

Ryan Wynott
1987 780 turbo+m46
 
A V8 780 would be pretty dope actually.

As far as the f body diff ratio whatever, ask any volvo performance shop what diffs come back broken.
And a 4.10 would make matters wors ein your above example. You're missing the concept. ;)
 
Now, I would have no problm agreeing that the 780 is a nice choice, but it never came in a wagon, there's an idea to play with 8)

Late
 
Hey, 780GT what wheels are those on your ride?
They look Italian about 17"x7.5" 20mm offset.........
How much do they weigh?
 
2 780s said:
Hey, 780GT what wheels are those on your ride?
They look Italian about 17"x7.5" 20mm offset.........
How much do they weigh?
Click to expand...

That car isn't mine. They are polaris 17x7, not sure about the weight. Lots of people have those rims so somone should know how much they weigh. I should have team dynamics monza 17x7 this season. I think they closely resemble the factory wheel, only 2" bigger diameter (and wider) and should look quite nice. Will depend how much the finishing touches on the 16V cost. :D

Ryan Wynott
http://bertone.wynott.ca
1987 780 turbo+m46
 
My experience with diffs has taught me that:

Big/strong rearends can handle big HP regardless of ratio.

Small/weak rearends break under high HP regardless of ratio.

I understand torque multiplication, but I've never heard of anyone suggesting that switching ratios (G&P) will cause a diff to be more likely to break.

The highest load on the diff happens when the car is stationary, the revs are up and the clutch is dropped and KABOOM. I've never broken a rear on the highway.

Kenny are you talking about breaking diffs or twisting and snapping axles?
 
I've been doing research on the rear end options as well for my '84 240 wagon.

I've decided to go with a '94-98 mustang 8.8 rear end, because it has rear disc brakes and most come with limited slip. It would need a different ring and pinion, think the highest they came with was ~3.27:1.

Or use a 1987-88 Thunderbird Turbo Coupe rear end with 3.55:1 or 3.73:1 ratios and use rear disc and traction-loc.

I've chosen to not have the axles shortened (save money), it should be about 1.5" wider, so .75" on each side centered, shouldn't be too bad. The plan is to try my hand at bodywork and fab a subtle wide-body flare, with the help of others and use a set of Cobra ultralite 17x9" wheels.
 
You must log in or register to reply here.
Back
Top