Im assuming my 77 LTD II has the 28spline version of the 9 inch? What other vehicles would interchange as far as a 3rd member? Im considering dumping the 2.50 airplane gears for something a bit lower. Maybe a 3.00 or 3.25.
It's pretty easy to swap pumpkins, and any of the '72-'79 Intermediates can have your requested ratio. Although, Babe has 2.47 gears, shoddy exhaust (shhhhh, without certain components....) and my lead foot, she moves out pretty darned good!
This car didnt do horrible from like...30-70. 0-30 was kind of painful though lol. I was curious cause my pinion seal is leaking anyways...and i found a whole rear from a 74 torino with a 3.00 i was thinking about nabbing for like 125 bucks. Ive pulled the pumpkins before on trucks...i even saved a 3.25 one untill i realized it was 31 (or 35 cant remember) spline
Regarding the pinion seal leak, check the end of the diff's vent tube. I had a pinion seal leak, and found out the end of the vent tube was plugged by a mud dauber wasp. It's gotta vent somewhere...
Is the diff an 8" or a 9"? I thought the pinion on the 8" is in the diff housing whereas the pinion on the 9" is separable from the diff housing. If it does have a 9", you only need remove the pinion assembly, break it down to install the new seal, and then if it has a crush sleeve, measure the thickness and replace with shims, then reassemble and reinstall.
I thought the 8 inch was used in the compact stuff? Ill have have to check mine. Im 99% sure its a 9 inch
Yes, you're right. I just posted this to show that both 9" and 8" rear ends have removable center sections and pinions.
Ha. Ha. Haha. Actually, 1) I stand corrected on the 8", I had to zoom in to see, and 2) I've only worked on one removable carrier, and it was a Toyota unit. Anyway, pulling the pinion and yoke will give you the chance to replace the seal, shim the pinion vs. using a crush sleeve, and service the diff fluid.
Ive only messed with one pinion seal and it was on an early 8.8 inch rear. It didnt go very well. Which is partially why i was nervous about this one. The yoke nut on the 9 incb is it one time use like the 8.8? Thats what caused my issue. I didnt know it was anf i reused it and the yoke kept wobbleing loose which took the bearing and u joint with it.
That's a good question. The few I've done, I spooged red Loctite on the threads and held the pinion and yoke from moving while I torqued the nut. It's possible you crushed the crush sleeve beyond where it should've been crushed, not that the nut backed off. That would then be a good reason to replace the crush sleeve (if this axle has one) with shims. They would allow proper torquing of the nut.
So i found a place that will sell a stock style, rebuilt 3rd member for 649. (Unless you want certain ratios it costs more) Anyways....according to the RPM calculator at 70mph with a 3.00:1 id be cranking around 2700rpm. 2900 with a 3.25. My current 2.50's run around 2300. I do want to roadtrip this thing some...which will involve 70 or 75mph freeway running for atleast a few hours. Do you think the 3.25 or even the 3.00 would string it out to much? Make it unbearable on the freeway? After seeing those RPMs im tempted just to stick with the 2.50's lol. I know an AOD is an option but...id rather not.
If you're planning on road trips and decent mileage, stick with the 2.50's. I road trip the hell out of my '65 289 T10 with 2.80's, and average between 17 and 20 mpg. It runs 2400 at 60.
Back when i used to DD this car id get about 20 cruising around at 55 lol. I may stick with the 2.50's now
Yeah, the magic RPM number at 55 MPH is actually 2000 if you plan to road-trip on the Interstate, but make the engine also last you. Babe is close to that with 27-28" dia. tires and 2.47 ratio. Not tire smoking off the line, and it's a 1-wheel peel for sure, but for 3800 pounds, she does well. I've had her at 85-100 on Texas highways, turning about 3200-3500. Imagine your rig doing that at 65-75 with a 3.00 or 3.25 ratio.
My RPM at 70 is 2300 with a 9 inch 3.70 and reworked AOD (with R4/70W internals; 5.0 with heads, cam and intake), 25.6" tires...it gets "decent" gas consumption (around 20mi/gal but if in city driving more like 12mi/gal) on the freeway if I keep my foot out of it...just food for thought....
And that's how the AOD is designed to work, your best direct MPGs are highway only, and combined overall will be less than your highway only, as it's an average. I was surprised Babe got 16 from WA to TX, in Winter, hauling 600 or more lbs. of cargo.
