3.23 vs 3.55 8/34

[shadango]

I have had my sights set on getting a 742 center section so I can run 3.55 gears and a suregrip.

Well, that combo aint just showing up used yet....and new is kinda pricey.   I know Carlisle is right around the corner.....but....

Locally I found a 742 with 3.23 open gears.....asking $125. ( They dont have pics or anything to send me.....its about a 60 mile drive to the guy.)

Seems reasonable, right?  What should I look for as far as thecondition of the unit if I go look at this? I figure I can have it rebuilt with 3.55s and a suregrip at some point...in the meantime try the 3.23s?

Or should I skip right to the 3.55s and not bother?

[dodj]

What's in your car now? 2.76? If it was me I'd go 3.73 or 3.91, but at least 3.55. You have a 318, so a little gearing will do wonders for 'waking it up'.
I'd try to find a sure grip rather than buy an open set though.

[Moparal]

Wade  (bullit99)  has 323's in his challenger. It's a 340 1973 challenger with a stock cam. He can spin the tires just mashing the pedal with ease. 323 is excellent for long cruises. The 355's might not be as friendly with the higher rpms , but there really isnt much of a difference. Also there are lots of 276 sure grip centers forsale all the time fairly cheap and it is very simple to swap the cones out

[shadango]

Well, I figured that since the 742 is the more desirable case and it has the 3.23s in it, I could try and find a suregrip center for it (clutch type) or even buy one new....along with 3.55s......in the meantime , run it as-is hopefully.....

I have been keeping my eyes open and I havent found ANY 2.76 suregrip units....the 2.76s I have now have NO  real low end at all.....and I think the 3.73 and 3.9s would be too much for the highway driving I want to be able to do.  3.55 seemed like a good compromise.  The 3.23 might be worth a try if it was already siting in my garage while I look for a suregrip unit and a gear set.  I would be having it all redone by a pro.

So if i were going to look at a used 8.75 chunk, I guess I would be looking for obvious damage and such, a "good" pattern in the gears...anything else specifically?

[dodj]

The 489 is the more desirable case. Larger yoke etc.. And you're right, the 3.7, 3.9 gears are not the best for extended hwy use, just fun on the street/track.

[Chryco Psycho]

I would grab the 3.23 for that price
it will definatly be ebtter than the 2.76
the 742 is actually stronger although slightly smaller than the weaker 489 unit , the 489 used a crush sleeve which is problematic but can be replaced with a solid spacer & use shims to improve the strength 

[dodj]

I've never read where the 489 is said to be weaker. The 742 is more desirable from a set up point of view,  but not more desirable from the strength angle. At least that's what I see written in the majority of forums/articles.

[Chryco Psycho]

the crush sleeve is the weak link , I ate 37 teeth off the ring gear when the crush sleeve collapsed under load in mine

[shadango]

I am pretty sure I want to go with the 742, both due to the shim/crush sleeve issue but also because the 489 would use the cone type ls and I want the clutch type.

So if i were going to look at a used 742 chunk, I would be looking for obvious damage and such, a "good" pattern in the gears...anything else specifically?   

[SBDave]

I'm building a 489 3.55 trutrac 3rd member up right now. The solid spacer kit seems pretty straight forward. I should have the car back running in about a week.  I'll let you know how it drives.  The car has a 318 904 and was a 2.76 open diff.

-Dave

[shadango]

Well, here I go with having second thoughts again.

Just looked at some prices on feebay......

A set of new 3.55 richmond gears is running about $280 or so.....a new tru-track like $550.....if I buy this 742 for $125, thats $950 already...PLUS whatever it will cost for someone to rebuild everything for me......

Dr diff has the same setup for around $1100 i think....

Suddenly that 742 I found isnt looking as attractive....It looks like it might be just as cost effective to buy the whole dang thing already done.

I mean, last year at carlisle I saw some rear ends and they were all going for $500 or so...and theywould need redone....parts and labor, again probably at least a few hundred bucks....

    

[challengermaniac]

I'm very happy with my 3.23 gears with a Suregripe carrier behind my 340.  I won't go to the 3.55 gears until, when/if I ever put in a 4 speed auto as I just don't want to run the higher RPM's on the freeway with lower gas mileage.

[vinb]

I almost forgot, but I need to take out the 3.55 and put in my 2.76 for Carlisle.

I really want to hear my stereo for the 3hr. trip and not get a headache. the only problem is I'll have to watch my speed....

[shadango]

I'm very happy with my 3.23 gears with a Suregripe carrier behind my 340.  I won't go to the 3.55 gears until, when/if I ever put in a 4 speed auto as I just don't want to run the higher RPM's on the freeway with lower gas mileage.

I was using that online RPM calculator and it didnt seem like there was that huge a difference between 3.55 and 3.23 RPMs at a given speed?

Would 3.23s really be a jump up from my 2.76s?  I just have so little low end right now.

[BIGSHCLUNK]

NIKKI'S got 3.23's great for hwy cruisn'!