[ry57pont]

i need to buy a center chunk. i have previously used a 3.73 ratio in my 10 bolt. i was planning to try a 3.89 in my new 9" but.... i found a used cener with a 3.70 at a good price. my question is: would i cut better ET's with a 3.90 vs 3.70? or is it just splitting hairs? my 4 spd ratios are 2.20 1.64 1.28 1.00 and i do drive on the highway so 3.90 ws going to b the absolute deepest i am willing to go. Thanks - RB

[andrewT]

what is your rear tire size? what kind of cam are you running and what are you normally shifting at?

[ry57pont]

27 10.5 15 tire. using a crower solid 60311 and shifting at 6K

[andrewT]

imo it would be a wash, but then again I am just a newb. I think you MIGHT see a better ET with the 3.90s, but if you can get the 3.70's for cheaper then its up to you.

play around with some calculators with your desired trap rpm and tire size.

[Bill Meyer]

Ryan - I have tried them all, 370:,390: & 410:. There is not much, if any, ET difference in any of them. Most Pontiacs make enough torque at lower RPM , not to require to rev the snot out of them like some other brands. Other factors, such as traction, weight, air, and did I mention traction, make a bigger difference. A little bog in 1st gear might not be a bad thing! I know you drive this thing on the street, so I would go with the 370:. - Bill -

[andrewT]

Originally Posted by Bill Meyer

Ryan - I have tried them all, 370:,390: & 410:. There is not much, if any, ET difference in any of them. Most Pontiacs make enough torque at lower RPM , not to require to rev the snot out of them like some other brands. Other factors, such as traction, weight, air, and did I mention traction, make a bigger difference. A little bog in 1st gear might not be a bad thing! I know you drive this thing on the street, so I would go with the 370:. - Bill -

what gears you running in yours Bill?

[ry57pont]

thanks! the 3.70 would save me about 500.00 over buying one new from moser.

[punisher#1]

i would go with the 3.70 if the deal is that good.
when we used to run steve's car with the 500hp 412ci, we went from 3.73 to 3.90 to 4.10 to 4.33s searching for et and 60 ft. the only thing that made it quicker was building a bigger more powerful engine.
pontiacs put out so much torque over a wide band, the difference in et's will be in the hundredths, if any.

[screamingchief]

What case does the "used" center section have?

If it's an OE center section,then I'd probably pass on it. JM2¢

The aftermarket nodular centers are much stronger than the OE centers are,even the OE Nodular centers.

I do agree on the whole gear ratio thing,as it will likely be NBD.

But I would'nt wanna invest any $$$ in an OE center section that I know is weaker,that is not unless I absolutely had to.

Though the aftermarket center section is'nt worth a $500.00 premium by itself,maybe $325.00 to $350.00 or so would be more like it,as that's what those aftermarket nodular centers cost.

FWIW

Bret P.

[Bill Meyer]

andrew T - I had been running 3.90 for about 6/7 years. Last year I tried a PG and switched out to 4.10 (it was time for new gears). I took the PG out and put back the T-400. I kept the 4.10. The times were the same. Prior to that, I had 3.70. The times were very similiar. More difference in ET's has been seen with torque converter changes than with rear end ratio changes. - Bill -

[Ron H]

I switched from 3.89's to 4.11's and picked up 2 mph but the et was at most .02. The reason for the increase in MPH was the 4.11's helped the converter out so it slipped less. Finish line rpm's were nearly identical.

[ry57pont]

Originally Posted by screamingchief

What case does the "used" center section have?

If it's an OE center section,then I'd probably pass on it. JM2¢

The aftermarket nodular centers are much stronger than the OE centers are,even the OE Nodular centers.

I do agree on the whole gear ratio thing,as it will likely be NBD.

But I would'nt wanna invest any $$$ in an OE center section that I know is weaker,that is not unless I absolutely had to.

Though the aftermarket center section is'nt worth a $500.00 premium by itself,maybe $325.00 to $350.00 or so would be more like it,as that's what those aftermarket nodular centers cost.

FWIW

Bret P.

it is a moser N 3.25" case with pro/stret motive gears looks like everything inside is moser as well. 28 spline pinion with daytona support.

[screamingchief]

Originally Posted by ry57pont

it is a moser N 3.25" case with pro/stret motive gears looks like everything inside is moser as well. 28 spline pinion with daytona support.

Then it does sound like that would be the best all around value in terms of strength per $ spent.

Gears would be easy enough to change later on if you did'nt like what's in there already.

Good luck with it Ryan.

Bret P.

[grandville455]

Ryan what spline axles?

[ry57pont]

Originally Posted by grandville455

Ryan what spline axles?

35 spline.

[grandville455]

Thats a good deal! I paid 995 for mine.. Spool I am guessing?

[ry57pont]

yes steel spool.