Discussion Forum - Northstar Chevelle Club

SShink · 3K+ Club

3.36:1 or 3.55:1?

more ambition than brains · 1K+ Club

Nothing scientific here.

Biskwik is getting 3:55 gears with really tall 2:65 x 70 tires with a standard Muncie.
My original Biscayne had 3:73 gears standard muncie, whined a little a 70 mph. mid 33-3400 rpm. Similar really tall tires.
Also Biskwik car was ordered with 3:55 gears.

78 Malibu with 200r 2:25x70 rear tires will probably get 3:36 because of the overdrive.
66 El Camino with 700r4 has a 3:73 with 2:45x60 shoes.

All three of these gear choices have not been test driven.

Biskwik in process, Malibu pending, and 66 elky still scattered all over the place.

The 200r with either 3:36 or 3:55 should be pretty snappy out of the hole, and, give you ok cruising rpm's so you don't feel too guilty at 75 mph.

Decide what means the most to you and go from there.
All cruising, no drag strip, orrrrrrrrrr?

Karl

Lost in the 60s · President

The 200r4 already has a much deeper 1st gear than the TH350 in the car, just changing that would improve acceleration a bunch. I would stay with the 3.36 for freeway. Between the lower gear in the trans and the 2.73 to 3.36 change, you are nearly doubling the ratio from dead stop. You can hold the trans/converter from going into overdrive/lockup for city/street driving and keep the rpm from lugging the engine. You would feel very little difference in the ratios, in a side by side drive test anyway.

Jon H · 1K+ Club

I agree I don't know if you would feel the difference given two identical vehicles to drive with only the gear ratio changed. With that said I have the 3:55 and have no reservations, best of both worlds.

Lost in the 60s · President

I also recommend leaving the trans configured for a lock up converter. I had a HUGE problem with mine getting too hot in the '38 a couple weeks ago, pulling the trailer back from MO against a headwind. I called Hughes Performance last week about a custom built towing converter and they claim the conversion to non-lock up creates an internal restriction that only adds to the heat soaking I was experiencing. At some point this year, I will be removing mine to convert it back and getting a lock up converter. I will most likely be employing Chris again to swap in a lower gear set in the axle too.

Larry Lucast · Active Member

I have had 700- and 200- R4s with 3:55 and 3:70 gears. With overdrive and lock-up, cruising RPMs are not much over 2,000. And low end is great.

67ss · 1K+ Club

You should also take into account for camshaft size to some degree. Having a big cam and loping along At 1500 does not go well together. If you plan on putting in the motor we talked about awhile back I would go with the 3.55.

SShink · 3K+ Club

Thanks everyone for the feedback.

I had 4.11's with a 200R4 in the blue '72 couple a few years ago, and those were too deep and still ran too high RPM on the highway even with OD, so switched those out to 3.42's, which worked well other than it was with the 468 BBC, so it was still a thirsty combo.

I'm leaning towards the 3.55's as a nice compromise, and with the SBC instead of a BBC it shouldn't be quite as thirsty on the highway.

Chris P.-Yes, that type of engine combo is still on my radar in the future, so I'm thinking the 3.55's are a better choice for something with a little larger cam in it as you said.

SShink · 3K+ Club

John D., you can 'un-sticky' this post. I'm not sure how it got that way. Thanks.

67ss · 1K+ Club

It does not appear to be sticky when I went in and looked at it Stan.

SShink · 3K+ Club

67ss wrote:
It does not appear to be sticky when I went in and looked at it Stan.

Thanks Chris. I see the post it note icon, but I think it's what got put on the original post like the 'two cents' or 'question mark' symbols, and not an actual sticky.

OscarZ · Mega Poster

3.73

SShink · 3K+ Club

OscarZ wrote:
3.73

I split the difference and went with the 3.55's. They are shipping from Quick Performance in Iowa this week.

SShink · 3K+ Club

Well, first install snag today... after removing the axle's to put the posi in, the driver's side axle was too pitted and flaked to put an axle saver bearing on it, so a mad scramble looking for a good axle, and none of the shops in town had one. Luckily another kind hearted Chevelle guy in the club here had a good one from a 10 bolt in a frame that came with a project car, so a swap took care of that. Gotta love Chevelle people!

The old trans is already out and the 2004R is in. So now it's up to finishing the posi install and seeing how things work together. Hopefully I get it back in 1-2 days.

6-27-17 2534.jpg

Out with the old greasy trans:

6-27-17 2540.jpg

And in with the new:

6-27-17 2539.jpg

67ss · 1K+ Club

It is always something when you are dealing with old cars. Mike's is going in on Monday to get the exhaust fixed.

SShink · 3K+ Club

67ss wrote:
It is always something when you are dealing with old cars.

I've decided there are two approaches to old car restoration:

1. Do it a little at a time, but plan on replacing parts in 'systems', or you'll have surprises or an old part will break right after you put in a new one, and bleed cash slowly or in chunks.

2. Do it all at once as a frame off and bleed profusely with all new parts, then the pain mostly goes away but the bills don't.

Neither option is pocket book or frustration friendly, but I guess we all like the challenge or we wouldn't be in the hobby.

Lost in the 60s · President

I don't know if it is as much a hobby as addiction...

I got a check for my share of the proceeds from the sale of my dad's house in May and used half of it to pay down our mortgage balance by 50%. My wife's mom had passed a few weeks before and she got a check from life insurance last week and paid off the rest of the mortgage. I could've dropped the Chevelle off almost anywhere and had a head turning paint job for what I paid on the mortgage, but owing NOTHING on all that we own is a REALLY great feeling...

67ss · 1K+ Club

I forgot to ask what did you end up going with for a convertor? I know you went lock up but what size stall?

SShink · 3K+ Club

67ss wrote:
I forgot to ask what did you end up going with for a convertor? I know you went lock up but what size stall?

I went with an 1800-2200 stall. Here's the link: Torque Converter Link

Hoping to get the car back today, as everything is installed but the mechanic needs to take it for a test drive, and of course we have heavy rain and thunderstorms today. I'm fine if he drives it in the rain, but with the soft tires and an unproven drive line, I don't want to put him at risk either.

Mitch-That's awesome that the house is debt free! That just means more cash in the pocket for car stuff, just in smaller amounts than if you would have used all the cash up front.

SShink · 3K+ Club

Well, as usual with these kind of projects, I'd say the success level is at 95%. The trans/gear combo is working great, and I'm within 100 rpm of the calculations without the electronic lockup converter working (that's the 5% issue that's still open).

The trans is shifting into OD at 2200 rpm, which is where I would expect it to with an 1800-2200 rpm lockup point, but I had to disconnect the lockup electronics from the trans as the solenoid must be wired differently since the brake light fuse keeps popping when the controller is connected to the trans. I had a similar problem with the convertible install that the pinout was slightly different, and I had to change it to work with the controller. So, I'll have to get out the trusty ohmmeter and check the pins on the trans and see what I need to change. That should get me the extra 100-150 rpm drop I'm looking for.

The mechanic did have one interference area with the exhaust as well Chris P. When he moved the cross member to the back holes, the passenger side had to be 'tweaked' a little, but it's all good now.

Otherwise, I didn't get on it too hard yet driving it home to give the differential and trans time to get happy with each other, but I can tell already it has more seat of the pants grunt, and it sure was nice cruising 70 mph at 2200 rpm!

Can't wait to get more miles on it to hopefully drive up to the SMN's and see some of you there.

67ss · 1K+ Club

Stan if you tell me the what year GN that the trans came out of I can try and post a diagram for the tcc circuit.

SShink · 3K+ Club

67ss wrote:
Stan if you tell me the what year GN that the trans came out of I can try and post a diagram for the tcc circuit.

Thanks Chris. 1987 GN

67ss · 1K+ Club

tcc circuit.jpg

-- Edited by 67ss on Friday 30th of June 2017 02:14:04 PM

SShink · 3K+ Club

Thanks Chris!

Looks like I need to connect into Terminal 'A' from the diagram you attached to get to energize TCC Solenoid, correct?

The B&M instructions says that's the lower left pin on the trans connector, correct? Do you have a pin out on the trans connector?

I have a feeling the B&M +12V wire is on the wrong connector currently.

Attached is the B&M schematic (See Fig. 3):

67ss · 1K+ Club

The connector on your B&M kit should have letters embossed into it if you look close.

Pin A should be 12 volt feed going into the transmission to feed the solenoid typically through a brake switch and pin D is the one getting grounded to turn the solenoid on.

SShink · 3K+ Club

67ss wrote:
The connector on your B&M kit should have letters embossed into it if you look close.
Pin A should be 12 volt feed going into the transmission to feed the solenoid typically through a brake switch and pin D is the one getting grounded to turn the solenoid on.

You were right that the B&M connector designated the 'A' pin, but what I found was the connector was 360 degrees out of orientation, so it was upside down and the latch was on the wrong side. I did some interweb research, and found some posts that the Buick GN guys cut new slots in the connector to flip it in order for the 'A' +12V and 'D' Ground connections were in the right place. So, a few seconds with the Dremel tool and it connected correctly.

I still need to walk through the controller wiring as something isn't right with the brake switch wiring as I was getting a constant 12.5V at the controller through the switch and it only dropped to 12.1V when I hit the brake pedal, so I think I tapped into the wrong side. I'll have to slow down and walk myself through it again. It shouldn't be this tough...

SShink · 3K+ Club

SShink wrote:
67ss wrote:
The connector on your B&M kit should have letters embossed into it if you look close.
Pin A should be 12 volt feed going into the transmission to feed the solenoid typically through a brake switch and pin D is the one getting grounded to turn the solenoid on.
You were right that the B&M connector designated the 'A' pin, but what I found was the connector was 360 degrees out of orientation, so it was upside down and the latch was on the wrong side. I did some interweb research, and found some posts that the Buick GN guys cut new slots in the connector to flip it in order for the 'A' +12V and 'D' Ground connections were in the right place. So, a few seconds with the Dremel tool and it connected correctly.
I still need to walk through the controller wiring as something isn't right with the brake switch wiring as I was getting a constant 12.5V at the controller through the switch and it only dropped to 12.1V when I hit the brake pedal, so I think I tapped into the wrong side. I'll have to slow down and walk myself through it again. It shouldn't be this tough...

I think I figured it out, and now that I think about it... I ran into the same issue on the last conversion I did. I believe the factory brake light switch is NO (Normally Open), so there's no voltage available until you hit the pedal. What I need is a brake light switch that is setup for a cruise control that has both NC and NO (Normally Open) contacts so that that the TCC switch receives 12V once the controller turns on the solenoid until the brake pedal is pushed and interrupts the 12V to the solenoid and the controller.

Looks like O'Reilly's has this one in stock, so I'm going to pick it up and give it a try. Cruise Control Brake Switch Link

Chris, does that make sense?

67ss · 1K+ Club

That switch may work, check each set of pins to see if they toggle opposite. But you are correct in your thinking of how it should work.

SShink · 3K+ Club

Success! Amazing how well things can work when they're installed correctly...

It runs out really nice around town, and I have the converter locking up at 42 mph, so it's not slipping around town and generating heat, or running at as high an rpm.

The electronic lockup got me the extra 250-300 rpm I was looking for on the highway:

60 mph = 1800 rpm

65 mph = 1900 rpm

70 mph = 2000 rpm

75 mph = 2200

Running the AC (which is running COLD and I'll never live without it again...) raises the rpm 50-100 depending on throttle conditions.

I still need to adjust the shift points a little lower as they are pretty firm and almost throw the car forward when I really get on it (can really tell the deeper 3.55 gears vs. the 2.73's), but I'm still taking it easy on the new parts and haven't done a full throttle run yet.

Now for some time to let the new trans and rear end to get happy with each other.

SShink · 3K+ Club

One other tidbit on the project. I kept the column shifter since it still has a bench seat and I don't care for any of the aftermarket automatic floor shifters, so my mechanic was able to use the stock linkage with the trans. All that was left was for me to swap out the gear indicator in the dash with one from Shiftworks for the OD gear.

Before:

7-5-17 2406.jpg

After:

7-5-17 2408.jpg

And the indicator lines up with all the selections!

The KC club has a cruise on Sat. to an air museum and downtown cruise-in in Topeka, so I plan on putting some miles on the Chevelle to prepare for the 6+ hour drive up to the Street Machine Nationals.

Larry Lucast · Active Member

The new indicator lens is a nice touch!

SShink · 3K+ Club

Larry Lucast wrote:
The new indicator lens is a nice touch!

Thanks Larry. Sometimes it's the little details that get me excited about a project. I like seeing this kind of stuff when I look at other cars too.