4.10 rear end gears!! Arghhh

[RetroSBK]

Even with the 700R4 locked up, with 295/50/16 BFG's on it, Im turning 2500rpm cruisin on the fwy here, and I pretty much have to stay in the right lane (70mph is WAY slow on the fwy here! So cal!)

Im thinking about switching back to 3.42's.... The problem is... the rear end is new, new Posi, and the rear end built with all new bearings, 5 lug axles, etc..

Thinking about maybe looking for someone to trade out with a tight Posi'd 3.42 or... I dunno

Just a bit too short, hell, with the motor in it now, I could run 3.08's with no issue, but cruise would drop way down...

72mph = 2500 rpm - 4.10
72mph = 2100 rpm - 3.42
72mph = 1900 rpm - 3.08

The drawback is that I have a Victor intake with a spacer, and where it has plenty of git, it will be runnign a bit below the torque curve with the lower gear, and with it the loss in mileage...

Ideas?? Wanna trade? lol

Will

[GREASEMONKEY72]

cant you take the 3.42 ring a pinion and and put them in your new one so you have the best of both, and i dont think id go lower than that because you do want to have atlest some rpms otherwise the converter will be slipping and heat up to much, but i could be wrong, wouldnt be the first time

[kwmech]

Those numbers do not sound correct. How tall are your tires? 4.10 gears with a 700 in 4th gear become 2.95s before the lock up convertor.




I looked up some stuff, tires must be about 25-26'' tall. try this link for calcs


http://www.florida4x4.com/tech/gearcalc.php

[RetroSBK]

I checked it with that calculator too and its right on... 2500 =70mph. Tires are 27.6 tall according to BFG's site..

Guess I could throw taller tires on it, but it kinda kills the "look" lol

[WorkinLonghorn]

Personally I think 23-2500 RPM is a good cruise RPM. My problem is that I'm doing 60MPH at 2500,so I definately hug the right and watch my mirrors.
>>My last '69 came with a 3.08 and 33" tires and got lousy freeway mileage.
>>Not sure I'd change that set-up of yours.

[meathead95]

my 86 lwb has a 700r4 and 308's from the factory and it does just fine.

[powell72]

Originally Posted by GREASEMONKEY72

cant you take the 3.42 ring a pinion and and put them in your new one so you have the best of both, and i dont think id go lower than that because you do want to have atlest some rpms otherwise the converter will be slipping and heat up to much, but i could be wrong, wouldnt be the first time

The carrier split is at 3.42 and lower (numerical), and 3.73 and up. I agree with you on the rpm's. I heard you don't want to run a 700R4 under 2K in overdrive.

[67ChevyRedneck]

^about 2000 to 2400 seems to be the "happy range" for the 700R in my truck. I have a 3.73 rear.

I have 235/75/15 on my truck and she turns a little more than 2100 rpm at 70. It's really nice

[paaw]

try some 373 gears, and a 60 or 65 tire

[GREASEMONKEY72]

ive got the stock TH350 with 3.07s and 29ish tall tires (side wall says 31) and i turn i think 3400rpm at 75mph i think i dont really remember

[skchevota]

What rear do you have, 10 bolt or 12bolt? If you can use the same carrier then put some 3.73 in it, that will drop you to about 2100-2200 and then sell the 4.10s on e-bay. If you dont know how to set up gears then it will cost you labor but that is it. If shops in your area want to much to do the swap, ask the techs in back if they do side work.... It shold cost about $300 to do the swap.

[RetroSBK]

It has a 12 bolt... I do need the new carrier, but thats part of the deal, no biggie...

Id like to get the cruise RPM about 1900 at 70 mph, as we rarely drive below 80 on the fwy here in SoCal!

Dont want to change the tires right now, just about the right stance, so the gears it is....

BTW, anyone need some 20x9.5 torq thrust 2's? Chrome lip with black powdercoated centers? I was at powdercoater today, and they had a deadbeat customer that had them done... they want $1k for the set of 4... PM me if anyone wants the contact info...