GrandSportC3

Pulled out my Tom's 4.11 posi tonight as I'm replacing it with a 3.73 spool which I'm trading with Red79Vette454.. I'll have to have Van Steel transfer the pinion yoke tomorrow (the pinion yoke on the 3.73 spool is for 1330 series u-joints and the one on my 4.11 posi is 1350 series as my driveshaft u-joints are 1350 series) as I don't have a impact wrench to get the pinion yoke nut off... If all goes well, the spool should be in tomorrow evening!!

Here are the differentials.. My 4.11 posi diff on the left and the 3.73 spool unit on the right..

TheSkunkWorks

Olivier, with the power levels your getting into IMHO this should prove to be a good move, particularly the spool.

mrvette

Glad you got two mules to help hoist them things outta that trunk....

talk of a ball buster....

9 second quarter, I been following you escapades there, doing fine man, just fine as wine....

GrandSportC3

It is actually required to run a spool if you run below 10.0.. I've never raced a car with a spool before, so we will see if the car reacts any different..

GrandSportC3

The differentials aren't all that heavy.. The old posi is 107 lbs and the spool unit is 99 lbs..

I need the lower gear to run a 250 shot of nitrous.. Otherwise, I'd run out of RPM's...

427Hotrod

Double check the overall width of the axles. Those flanges look a lot thicker on the spool one....might be a factor with halfshaft length if you use old ones. Of course might be fine if the spool has the flanges pulled inward a like amount.


Good luck...it's going to like the 3.73's when you spray it.


JIM

GrandSportC3

Already did all the measurements.. The 4.11 posi is 13 inches from axle to axle (on the outside) and the 3.73 spool setup is 12.5 inches (actually narrower by 1/2 inch) BUT the spool setup comes with 1/4 inch spacers each side which makes it identical width of the posi setup!

427Hotrod

Cool....they did look like they were closer inward...but couldn't really tell. Just trying to head off heartache!!


Going racing this weekend? It will be neat to see a back to back motor pass against the 4.11's to see if it loses much. Maybe a tenth at the worst? The lighter spool etc might even cancel it out and be equal.


JIM

GrandSportC3

I'm planning on racing on Sunday..I'll make 1 or 2 engine passes and then flow the nitrous system with the 100 HP jets.. Will make a pass or 2 with the 100 shot but won't go with the bigger shot yet as I'm still using the Radial slicks and they are swaying really bad above 125 mph.. I'll feel safer once I'll get my new wheels so that I can install my new 28 x 10.5W - 15 ET Drags.. I know that I will lose a few 100's in the 1/4 mile due to the bias-ply design but I will get better high speed stability..

The spool isn't all that lighter.. Weighted both differentials and the old one weighted in at 109 lbs and that was with 2 qts of posi fluid in it and the strut rod mount attached.
The Spool unit weighted in at 99 lbs dry and without the strut rod mount. Adding about 5 lbs for the fluid and 2 lbs for the strut rod mount, there's maybe a 3 lbs difference.. Not a whole lot.. I expected more..

GrandSportC3

UPDATE!! Spool Differential is installed.. Going for alignment on Saturday. Should get my new wheels tomorrow and I already got my 28 inch tall slicks (ET Drag 28 x 10.5W - 15)

red79vette454

What kind of wheels you getting?

I can't decide if I like the Aluma stars or the Magnum 2.0 for our new setup. Either one will probably be 15x15 or 16x15 and have beadlocks.

GrandSportC3

I bought some New Old Stock Cragar Super Lites (set of 4) which are just about identical to Weld Drag Lites...
I will keep 2 sets of wheels.. One with 28 inch tall slicks for engine only or small shot runs and the 2nd one with taller tires for the full 250 shot (I might go with GoodYear 29 x 11 - 15 Dragway Special tires). Right now I have the Hoosier Radial slicks on there (29.5 inch tall)

The Magnum 2.0 are nice wheels but they are very expensive.. If I'd buy new wheels, I'd actually go with MT ET Drag wheels. Those are the lightest that I know..

comp

69 N.O.X. RATT

I am running a 33 x 16 tire on a 15 in. rim....beadlocks $$$$$$$$$$$ !!!!!!!!
I am considering them also. I need to find a wheel sponser !

You will like the spool Ollie...cept when you have to push the car around the slightest of a corner.

GrandSportC3

Turning any corners will be especially painful with the radial slicks. Once I'm back to bias-ply, it should be a little better.

69 N.O.X. RATT

Have you ever tried to push a car around a corner that has a spool? Trust me it does not matter what kind of tire is on it....the car stops dead in its track as soon as you turn the steering wheel. My car weighs 2400 lbs with me in it and it takes three or four guys to push it around a semi tight turn.

GrandSportC3

now that'll be fun

Hope that I won't need to push it too much

69 N.O.X. RATT

Ha ha...it is a race car....you will be pushing it a lot more than you want !!

GrandSportC3

I did my share of pushing already

TheSkunkWorks

I agree with 69 N.O.X. RATT. It's been a few years since I dealt with that, and I had almost forgotten about how much harder it is to push a car around with a spool. I've done my share of Austin Powers type multi-point turns, as the term "tire scrub" doesn't even come close to describing it...



...still, IMHO it's the right thing to do once you get quick, rule or no.