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Discussion Starter · #1 ·
What is the best way to ID your final drive ratio without removing the inspection cover? I've used Wes' math ( as I've recommended ina few posts) but there's too much room for error. Especially if you know your speedo is off and you guess your going 65 witht he flow of traffic.

I spun the driveshaft when both axles were up off the ground ( can't spin one tire at all when the other is down ) and it went around 3 1/3 times. Or at least, that what I wanted to see since it's supposed to be a 3.31. Yet, on the highway, at 65 ( with the flow of traffic - speedo reads about 52 or so )I'm spinning 2950 with 28" tires. At 70 ( roughly!) its about 3200.

The math shows 3.73's. And it feels like it too.

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2 thoughts:

First, can you find the axle numbers? That would be a sure way to tell

Second, have someone with an accurate speedo pace you on the highway so that you know that you're doing 65 mph instead of guessing.

Kurt

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The 68 Chevelle info page. [last updated Nov. 30, 98]
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Discussion Starter · #3 ·
Kurt, the axle numbers are irrelevant since the car's been gone through ( it had 4.88's for most of its life ). And I was going to enlist the aid of my pardner for the speedo check. Thanks.
 

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Gene,Gene, Gene there is no sure way without pulling the cover. There is too much room for error any other way. But if we are just guessin' then put me down for a saw buck on 3:55.
Harley
 

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gene
harleys right, there is no true way to do it with the cover on,but you can get damn close.
heres what I do.get both wheels off the ground. mark a tire at the very top with chalk.now go under and put a small dimple of duck seal on the very top of the driveshaft near the rear.now spin the wheel so the driveshaft goes clockwise.your in the threes somewhere, so turn the shaft three times by spinning the tire,now put the tire to the very top, same direction you were going, stop it there.now go under the car and look down the driveshaft.think of a ten didgit clock around your driveshaft near the spot ya put your duck seal pionter.if your pionter is pionting strait down(5 on a ten didgit clock) this would be 3.55 or close.(if it points toward 2 on a ten didgit clock)I would say 3.23.if it points toward the 8 on a ten didgit clock i would say 3.73 you could even cut out a circle and use it as the 10 didgit clock. I know this sounds crude,but this is the best way i found to do it without taking the cover off after all 12 bolts only had certian axle ratios just take the nearest one to what you come up with, it should prove to be right on. well hope all this B-S helps 67rat member #199

[This message has been edited by 67RAT (edited 07-21-99).]

[This message has been edited by 67RAT (edited 07-21-99).]
 

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Discussion Starter · #6 ·
Well gentlemen I have 7, yes 7, inspection cover gaskets.I'll guess I'll just have to waste one for a check. Fluid capacity anyone? I'll check the service manual.
 

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Most people I know just use RTV silicone instead of gaskets..

And if you clean up the area where the oil will pour out you can save it in a suitable container for re-use but it never hurts to change it cuz of course who knows when the last time it was changed was..


as for fluid amount, you are way better off buying a 5 gallon bucket of gear oil, ive found it to be about half the price of a quart/pint/etc and you dont have to ever worry about buying enough...

let us know what they turn out as (the gears)

Mike
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Discussion Starter · #8 ·
Mike, that's probably why the third owner had so many gaskets. BTW, I've been driving the Chevelle to work as my other car was in the paint shop. Well last night, after I dropped my son off at home, I remembered I hadn't dropped off a UPS overnight in the box up the road. ( important docs and checks). On the way back home, about 1 1/2 miles from the house, I go to grab second, whoops nothings there or third or fourth. Only first. Well my lady friend was kind and loyal enough to screw up just a short distance from my home minimizing embarassment to me and, most importantly, to my son who thinks the "racecar" is the coolest thing next to his fire engine. God I'm starting to love this bitch!


Gene Chas
Gold Member 62
'67 SS 396

[This message has been edited by Gene Chas (edited 07-22-99).]
 

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Gene, Harley's right. Awhile back he coerced me into pulling my cover. Yeah, it's a pain and a mess, but my kids just loved the smell of 90W permeating the garage :) Nothing quite like it. But it is well worth the peace of mind.

Put it on stands, pull the cover, spin the tire with your foot while counting the teeth on both gears. Count 'em a few times to get it right and ensure you're not doing this again for awhile.

I went the gasket route with some gasket adhesive to keep it in place. I had purchased 3 qts of 90W based on something I read somewhere, but it was full after 2+. Good luck getting the 90W in. You may want to buy a pump of some kind. After spilling the stuff all over myself, and desperate for a solution, I was "lucky" enough to find a hole in my trunk. I snaked a long hose through it and filled it via the trunk.

So I highly recommend performing this procedure (counting your gear teeth) before restoring your trunk :). Good luck.
 

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If you have the cover off, YOU DON'T HAVE TO COUNT ANYTHING! EVERY pinion gear that I have ever seen in my life (and that's a bunch) has the pinion teeth and ring gear teeth numbers stamped on the head of the pinion in plain sight following the stamped part number (as well as month /yr of mfg).

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Discussion Starter · #11 ·
Cool DZ, that's the first thing I'll check for. TK, I filled the Muncie by hanging the bottle in the engine compartment and snaking a hose down. I'll do the same trick from the trunk for the 12 bolt. And yes, it needs a little repaint so I'll do this first.Thnx guys.

Mike I've got 6 ( I fibbed - only counted 6 last night) gaskets so I'll use that with some High-Tack.



[This message has been edited by Gene Chas (edited 07-22-99).]
 

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Gene,

nice one with the tranny, man!

does Fix Or Repair Daily ring a bell?


anyway, i hope you get this sukin son back runnin soon enough!
 

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Gene, Since you didn't mention anything about loud explosions I am assuming your shifter linkage is the problem. On filling your rear end, if you raise the car and put the jack stands under the frame, the differential will hang low enough that a 4" piece of hose on the bottle will be all you need to fill it. By letting it hang it is a lot easier to get the cover off also.

BTW I stopped using cover gaskets years ago, they always seeped. I clean the cover and housing real good and run a bead of black RTV on the cover and bolt it on. If you can wait about a 1/2 hour before adding the lube. Doing it this way I have never had a leak.

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[This message has been edited by 64elcamino (edited 07-22-99).]
 

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DZAUTO is right about the stamping on the gear. Mine was tough to read so I counted teeth to be sure. Besides, I didn't want to find out later that I misread it.

Although I guess you've got bigger things on your mind right now with that tranny. Bummer...

[This message has been edited by TK-70 (edited 07-22-99).]
 

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Discussion Starter · #16 ·
Yeah, I'm guessing linkage. The tranny is strong. All thumbs over here hooked up my first 4 sp shifter and it feels like a rod fell off. I was having quite a time with those S-shaped retainers, guess I lost one.

No big shakes! I have a Chevelle shifter ready to go in so I can remount my console. I still haven't figured out how to rig the stock handle on it though.

Never a problem, only a challenge!


I was going to park her until I get the lap belts in and the console in anyway. Plus a few other little things.

My commute to and from work is over forty miles. Man, that little rat is thirsty! Espcially when I'm testing the dual accelerator pumps. Huwah!

Dyin to know what I've got in the back. Whatever it is I want a freckle more. The next motor is a real spinner. I'd like a bit more gear.



[This message has been edited by Gene Chas (edited 07-22-99).]
 

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gene
what ever ya do dont go to much gear,I have 4.88s in my L-88 wanna-be and its way to low,dont get me wrong,it goes to 105 in a hurry but thats it,shes done. the drivability
sucks,4.11s or even 3.73s would do me better, It kinda gets old driving 60 mph at 3800rpm.what gears ya going to?do you know the paint code on the color on your 67?That color is great,gives it a dark,mean ,stomp your hide look,dont worry,I wont steal your color for my 67,but I have a 62 chevy 1-ton 4x4 that might look good wearing it. well good day. 67rat member #199
 

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Gene,

500+ horses with street tires keep you traction limited up to 60 mph for sure. So set your first gear top speed to 50-70 mph, any lower is nonsense..

Also consider that with 4.88 the revs on 4th @ 60 are 4000! With 3.31 they are like 2500.

Your 1/4 would be approx 12.5 @115. With 4.88 your top speed would be 105 mph!!! Nonsense! I would set my third gear so that it is on power peak (6800) at 115 mph and leave 4th to hiway. Otherwise you just spend too much time shifting…

Conclusion, go with 3.31 or 3.73, any higher and the first gear is useless + high revs on hiway and limited top speed. All the more so with the NOS…
 

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Discussion Starter · #19 ·
Gentlemen, after research and analysis I bought a 3.73 gearset from Wally some time back. (Assuming I had the 3.31). If the gears now in her are 3.73, i'd like to go a bit deeper. If they're 3.31, perfect, the '73s will work perfectly.

I always thought 3.90s were best for street/strip. Richmond must make these for the 12 bolt. RAT, my bud who ran the 427 warned me about the same thing. Especially deep gears with a close ratio Muncie. Anybody have an M-20 they want to swap for a 21?

67RAT, wierd I hate the paint and everyone else says, "wow, great color". It a custom mix. The '67s paint code is RR, or Bolero Red in the 67 model year. I'd like to get it back to Bolero ( the trunk and doorjambs still are). Plus the paint looks OK on a scanned picture, but up close, it's a little rough. Age cracking and sloppy work with a paint gun. But if you want a chip off her, its done.

Hey Vortech, you're getting way too analytical on me! You mean to say that I should be between 50-70 in 1st at my shift point ( figure 6700 rpm ). I'll run the numbers on that. The M-21 has a 2.20 ( I can tell it must be an M21 cause its "louggey" in 1st with that 2.20 ), my tires are 28", and my final drive ??. That's the variable anyway.

My new front springs are too stiff to allow for good weight transfer. She behaves surprisingly well around corners, but doesn't lift like it should. It figures, I am undoing everything the last owner did. I don't think adjustable Konis or even 70/30s will help the stiffness. The ladders work OK ( but are fugly) and the BFG Drags are good. You may or may not recall, but my goal with this girl is an AIRGAP on launch. No, not an Edelbrock airgap, a '67 Chevelle Street Queen friggin drop the clutch, hook up and lift my front tires up off the tarmac. Double huwah! I see now that's going to take some suspension adjustments. Next year's mission. I hope its possible with a 4 speed and also that my new clutch takes the beating.

Anyway, thanks for all the rear end help. ( that's sounds like a Richard Simmons line - aaaargh)



[This message has been edited by Gene Chas (edited 07-23-99).]
 

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Gene,

You just can´t say that 3.90 is the best. All the gearing depends on the power, traction and purpose of the car.

BTW, The need for gear-box exists only when the engine is weak


I do not have any experience with 67s, even less with your combo, so i can´t really give you any bulletproof advice..

If you want a wheelstander, then you need some serious tires, which also stand deeper gears.

Do you know the basic-basic formula:
HP=(mph/234)^3 * weight (lbs)

So, if you have 500 HP, 3700 lbs, then 1/4 speed should be 120 mph.. Of course traction is a variable, also dyno/rw HP...

Still you need also some 130 mph potential on 1:1, if you go with a 200 HP or so NOS.

So, the first gear 2.2:1 will top around 60 mph anyway. Run the numbers depending on the tire size for rear end... very high 3s prob..

Are you sure 500 horses will do the trick?

just my 2 cents


[This message has been edited by vortech08 (edited 07-23-99).]

[This message has been edited by vortech08 (edited 07-23-99).]

[This message has been edited by vortech08 (edited 07-23-99).]
 
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