66 327 200-4R Rear Gear? - Chevelle Tech
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post #1 of 37 (permalink) Old Jan 5th, 20, 4:42 PM Thread Starter
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66 327 200-4R Rear Gear?

My '66 Malibu has been a ton of fun after upgrading to a 200-4R. It has a TransGo shift kit and an automatic lockup kit. Gears 1-3 are really great but my tire and rear end combo makes OD really surge. If I put my foot in it and get to 65, it will lockup just fine, but it doesn't work so well if I drive it regularly. So I think it's time to swap out the rear gears for summer cruising and occasional burnouts.

Current setup is 327, 200-4r, 3.08 rear, 27.7" tires. The tall skinny tires are staying because I love the look, it's a total sleeper/grandma car. I'd like to keep the 8.2" 10-bolt but would love to see it do an occasional two tire burnouts. So I need to make the changes in the rear gear. My RPM spreadsheet says I had been pulling 1600rpm at 65mph (hence the surging). A 3.73 ratio would be 2000rpm at 65mph. (The 200-4r was originally in a 442 w 3.73) Do I need to go even higher rpm at 65?

Where should I go for Posi and rear gear? I'm thinking Yukon Posi and Motive 3.73 or what else should I consider? What vendors?







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1966 Malibu 327 200-4r
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post #2 of 37 (permalink) Old Jan 5th, 20, 6:06 PM
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Re: 66 327 200-4R Rear Gear?

How does it run when you run it at 2000? Do you have a bit of a cam in it?

Jim

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post #3 of 37 (permalink) Old Jan 5th, 20, 8:13 PM
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Re: 66 327 200-4R Rear Gear?

The 3.73 gear /2000rpm should get you out of the surging zone. I worked for the gm dealership in the 80s and 90s and saw this very type of problem with many models as the idea was to lock the converters in both 3rd and 4th gears to obtain maximum fuel mileage. Even my wife's 4cylinder 90 Olds Calais had this issue. When you lock the converter too quickly in the rpm band, you will feel the pulsation of each cylinder firing as you have discovered.This is magnified if you have a aftermarket cam. Is your converter locking in both 3rd and 4th?
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post #4 of 37 (permalink) Old Jan 5th, 20, 11:05 PM
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Re: 66 327 200-4R Rear Gear?

HI
Considered a Tru Trac ?

Try and get a better quality cut crown wheel and pinion, it will be quieter. US gear do a street gear but for a 10 bolt ??

yes at least 3.73 would be a good starting point
'3.73 = 2000rm in 4th at 65mph
3.73 = 2900 in 3rd at 65mph

It really depends on your
camshaft
carby size and type V/S or Dp
inlet manifold

Last edited by swampy 6x6; Jan 5th, 20 at 11:24 PM.
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post #5 of 37 (permalink) Old Jan 5th, 20, 11:56 PM Thread Starter
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Re: 66 327 200-4R Rear Gear?

Quote:
Originally Posted by 77 cruiser View Post
How does it run when you run it at 2000? Do you have a bit of a cam in it?
It runs quite well at 2000 rpm, smooth and good on power. It has a bit of a cam in it. The spec card has been lost long ago since it was put in back in the 80s.

Quote:
Originally Posted by modern malibu View Post
The 3.73 gear /2000rpm should get you out of the surging zone. I worked for the gm dealership in the 80s and 90s and saw this very type of problem with many models as the idea was to lock the converters in both 3rd and 4th gears to obtain maximum fuel mileage. Even my wife's 4cylinder 90 Olds Calais had this issue. When you lock the converter too quickly in the rpm band, you will feel the pulsation of each cylinder firing as you have discovered.This is magnified if you have a aftermarket cam. Is your converter locking in both 3rd and 4th?
The converter is only locking in 4th. I will frequently put the car in only 3rd gear when I'm driving around town. It behaves really well through those three but I wanted the 200R4 for the OD gear. Hopefully this switch will make the difference.

Quote:
Originally Posted by swampy 6x6 View Post
HI
Considered a Tru Trac ?

Try and get a better quality cut crown wheel and pinion, it will be quieter. US gear do a street gear but for a 10 bolt ??

yes at least 3.73 would be a good starting point
'3.73 = 2000rm in 4th at 65mph
3.73 = 2900 in 3rd at 65mph

It really depends on your camshaft carby size and type V/S or Dp inlet manifold
I looked at the Detroit TruTrac but was concerned it was too expensive. It looked like the TruTrac would be the same cost as all of the other parts put together with a less expensive LSD. I have no problem spending money as long as it's vastly superior or more accurately fits my needs. I'll look into US Gear.

I really wish I had the cam specs for this, it would be super helpful. It originally had a Carter 600+ cfm but there was no choke and some idle issues, so we pulled a 750 Holley off a buddy's shelf and it has been running that with the 200. It's obviously way too much carb, so instead of messing with the jets of the 750, I ordered a 600cfm during the Holley-days. The 600 will go on when the rear gear goes in. Its running a Weiand single plane that I'd like to eventually swap out with dual plane for the street.

It sounds like my homework is to research US Gear 10 bolt options and TruTrac options compared to Yukon Posi.
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1966 Malibu 327 200-4r
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post #6 of 37 (permalink) Old Jan 6th, 20, 11:28 AM
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Re: 66 327 200-4R Rear Gear?

Hi
Engine 327 would be fine with an Edelbrock Perf RPM still make good street power . The dual plain builds torque early in the rev range and help with the overdrive lowered rpm . Worth a try because you would most certainly get better throttle response . U would get good topend still because your don't have a big inch motor.

A vacuum secondary will give great low part throttle acceleration especially for your overdrive lower rpm .
Any carb around 600 cfm will do . Brawler or Quick Fuel / Hot rod carb

To get the best setup for the engine dual plain /carby just go with new clutches and gears for the diff for now. The budget or the wife and kids get us all in the end !!

In regards the gears Us Gear came out with STEALTH gears just after I bought mine for the 9 inch . Give them a call u might be able to get a custom order/option for a 10 bolt even if there not in a catalogue.

If u were closer I would sell u my RPM manifold still in box !!

Measure the manifold vacuum will give some idea of the camshaft
above 12inches vac mild
9-12 inches vac mid range
4-9 inches of vac serious
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post #7 of 37 (permalink) Old Jan 6th, 20, 12:26 PM
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Re: 66 327 200-4R Rear Gear?

3.73 rear gears with that tranny work great. if you think your cam is too big, you could even do 3.9x or 4.1x gears and be good. your motor isn't a torque monster....so let the gears get you off the line.

your overall combo is not matched well, IMHO. lose the single plane intake and get an RPM intake. also, return the carb you bought and get a Street Avenger 670 or a 3310 carb.

go with an Eaton posi and ignore the True Trac options....however you want to spell that.

lastly, when all of this is done, have your motor professionally tuned. where the motor and combo will end up will be vastly improved from where it is now....IMHO.

'69 Malibu 383/TCI TH350/8.2 3.36 Eaton Posi. Street Edge 10" 2800, E-Tec 170s, Custom Mike Jones HR Cam, RPM Air-Gap, StreetAvenger 770, Pertronix HEI, Hedman 1 5/8" Headers, Moser Axles, PMT 1320R Kit. [email protected] 111 MPH, 1.6865 60 ft, Nitto 555
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post #8 of 37 (permalink) Old Jan 6th, 20, 1:26 PM
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Re: 66 327 200-4R Rear Gear?

Quote:
Originally Posted by brockmub View Post
The converter is only locking in 4th. I will frequently put the car in only 3rd gear when I'm driving around town. It behaves really well through those three but I wanted the 200R4 for the OD gear. Hopefully this switch will make the difference.
My car is nearly identical except that I already did the 3.73 posi. Even so, I manually shift into 3rd when driving through town because once in OD, you can get down quite low in MPH (30-35) before it downshifts at light throttle. I don't want to romp on it in town to downshift and it will bog if left in OD. This is more of a 2004r issue that a gear change won't fix.
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post #9 of 37 (permalink) Old Jan 6th, 20, 3:13 PM
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Re: 66 327 200-4R Rear Gear?

When you say "automatic lock-up", what do you mean? Does your trans shift 1,2,3,4, then locks up, or does it lock up immediately when it goes into 4th? I used to have this issue with my Camaro, even with 3.73's, before i stopped it from going into 4th immediately. I know some people dont want to be bothered with it, but i have my lock up on a toggle, even with the vac switch, it would still lock up at like 40 mph, and thats too low. so i just keep it off unless i am on the highway. i think i remember the 4l60E wouldnt go into lock up until 48 mph, if memory serves correct.

When you say surge, is it actually locking, unlocking, locking over and over? I dont think a gear change is going to fix that.

My Monte Carlo has 3.08 gears, and a 2004R, i let her run through 1-4 on around town stuff, and lock it up on the highway. My car doesnt do alot of awesome things, but it does run down the highway at 70-75 mph right around 1800-2000 rpms.
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post #10 of 37 (permalink) Old Jan 6th, 20, 3:58 PM
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Re: 66 327 200-4R Rear Gear?

Second on the toggle switch. Mine only locks-up in 4th, but it was still too quick so I installed a simple on/off switch under the dash. I only switch to lock-up when I'm on the freeway.

jim
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post #11 of 37 (permalink) Old Jan 6th, 20, 4:26 PM
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Re: 66 327 200-4R Rear Gear?

A 4.11 gear would put you at appox. 2300 rpm at 70 mph with your current setup and would greatly increase off idle acceleration. Best of both worlds if you ask me. I run a 5.3 ls with a 4l60e,3.73 rear gear and a 26.8 rear tire and see 2450 rpms at 70 mph.You have an inch taller rear tire and a .67 overdrive gear as opposed to a .70 in the 4l60e trans.Converter lockup would maybe drop this another 150 rpms.
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post #12 of 37 (permalink) Old Jan 6th, 20, 4:57 PM Thread Starter
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Re: 66 327 200-4R Rear Gear?

Quote:
Originally Posted by swampy 6x6 View Post
Hi
Engine 327 would be fine with an Edelbrock Perf RPM still make good street power . The dual plain builds torque early in the rev range and help with the overdrive lowered rpm . Worth a try because you would most certainly get better throttle response . U would get good topend still because your don't have a big inch motor.

A vacuum secondary will give great low part throttle acceleration especially for your overdrive lower rpm. Any carb around 600 cfm will do . Brawler or Quick Fuel / Hot rod carbTo get the best setup for the engine dual plain /carby just go with new clutches and gears for the diff for now. The budget or the wife and kids get us all in the end !!

In regards the gears Us Gear came out with STEALTH gears just after I bought mine for the 9 inch . Give them a call u might be able to get a custom order/option for a 10 bolt even if there not in a catalogue.

If u were closer I would sell u my RPM manifold still in box !!

Measure the manifold vacuum will give some idea of the camshaft
above 12inches vac mild
9-12 inches vac mid range
4-9 inches of vac serious
Called US Gear - no 10 bolt 8.2"

Thanks for the manifold vacuum pressures, that's pretty helpful. I'll keep that in mind.

Quote:
Originally Posted by blue_69_malibu View Post
3.73 rear gears with that tranny work great. if you think your cam is too big, you could even do 3.9x or 4.1x gears and be good. your motor isn't a torque monster....so let the gears get you off the line.

your overall combo is not matched well, IMHO. lose the single plane intake and get an RPM intake. also, return the carb you bought and get a Street Avenger 670 or a 3310 carb.

go with an Eaton posi and ignore the True Trac options....however you want to spell that.

lastly, when all of this is done, have your motor professionally tuned. where the motor and combo will end up will be vastly improved from where it is now....IMHO.
No love for the Holley 600?

I agree with you Blue. My combo is not matched well. I don't think this combo is set up for how I drive the car but instead what seemed cool back in the late 80s. I pulled the car out of a barn a couple years ago where it had sat for 20 years. It's doubtful that this motor was ever professionally tuned but I'm going to have a good shop look at it when done. The Edelbrock 2703 Performer is coming next, it has dual plane and an oil fill tube that I really like.

Quote:
Originally Posted by Dansk View Post
My car is nearly identical except that I already did the 3.73 posi. Even so, I manually shift into 3rd when driving through town because once in OD, you can get down quite low in MPH (30-35) before it downshifts at light throttle. I don't want to romp on it in town to downshift and it will bog if left in OD. This is more of a 2004r issue that a gear change won't fix.
That's what I'm trying to avoid with a proper set up of the trans and gears (even if you say it won't fix it). Hopefully with this set up, I can put it in drive and cruise. It's a great car for that. As I said earlier, it's got a a Transgo shift kit in it as well as the TCI lockup. When it hits 4th at slow acceleration, it wants to lockup, realizes it doesn't have enough power and releases. But it happens repeatedly, this is the surging that I'm talking about.

1966 Malibu 327 200-4r
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post #13 of 37 (permalink) Old Jan 6th, 20, 6:15 PM
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Re: 66 327 200-4R Rear Gear?

If I had your car, this is what I'd do :

Install a mildly calibrated quadrajet from SMI carburetors :

https://www.smicarburetor.com/produc...8/productID/47

The small primaries in the quadrajet will stop any surging you presently have.
Use a factory cast iron intake or a performer 2-0. Stay away from large plenum intakes like the performer rpm.

Install 3:55 gears. 3:73's would also be ok but I think you'd like the 3:55's better.

A powertrax locker is made for 8.2 rears. I've heard good things about them

https://www.summitracing.com/parts/p...hoCfMAQAvD_BwE
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post #14 of 37 (permalink) Old Jan 6th, 20, 7:16 PM
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Re: 66 327 200-4R Rear Gear?

TruTrac if you're going to keep the car and 3.73.

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post #15 of 37 (permalink) Old Jan 6th, 20, 7:46 PM
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Re: 66 327 200-4R Rear Gear?

Quote:
Originally Posted by brockmub View Post
That's what I'm trying to avoid with a proper set up of the trans and gears (even if you say it won't fix it). Hopefully with this set up, I can put it in drive and cruise. It's a great car for that. As I said earlier, it's got a a Transgo shift kit in it as well as the TCI lockup. When it hits 4th at slow acceleration, it wants to lockup, realizes it doesn't have enough power and releases. But it happens repeatedly, this is the surging that I'm talking about.
If your issue is lockup engaging at too low a speed, then here is a solution that will prevent lockup below a certain MPH. You can add it in series to your current lockup circuit and it will keep it from engaging below the MPH that you set.
https://www.ronfrancis.com/prodinfo.asp?number=TC%2D75
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