Transmission Rebuild Help - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 12-31-2014, 10:49 AM Thread Starter
 
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Transmission Rebuild Help

I have a 1967 Dearborn 3 Speed(built by FoMoCo) that I pulled out of my 1967 GTO and I would like to buy a rebuild kit for it, but I cant find one for the life of me. I am sure people on this site have found rebuild kits for the same transmission, I was just hoping someone could point me in the correct direction. Thanks!

Chris
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post #2 of 10 (permalink) Old 12-31-2014, 12:17 PM
 
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I have a 1967 Dearborn 3 Speed(built by FoMoCo) that I pulled out of my 1967 GTO and I would like to buy a rebuild kit for it, but I cant find one for the life of me. I am sure people on this site have found rebuild kits for the same transmission, I was just hoping someone could point me in the correct direction. Thanks!

Chris
The Dearborn HD 3-speed is a pretty good trans. Had one in a '67 Firebird and my present '68 Lemans. The only disadvantage is 3-speeds! If you decide to "run" someone, maybe a Chevy, the disadvantage is you can't downshift from 4-3 at cruising speeds to give you that jump in taking off. Have had a couple experiences where I could only matt the gas to the floor because I couldn't throw a down shift. They always walk away. Now from a dead stop, another story because the Pontiac engine has the torque to pull it.

The Ford Dearborn 3.03 3-speed is basically the same as the 4-speed Ford toploader. I searched the net and could not myself come up with anything specific for a Pontiac Dearborn 3-speed master rebuild kit. Here is a PDF you might want to download and keep for tranmission ID, disassembly & assembly. http://thefirstgensite.com/library/6...ce/PO67S7A.pdf

Next, the best I could find were under Ford suppliers, which should work. I believe the GM version simply changed out the input shaft/throughout bearing collar so it could be used in GM applications. I suspect the tailshaft might be different as well to work with the GM driveshaft input shaft. But guts wise, should be the same as any Ford toploader 3-speed which should be similiar to any toploader 4-speed -which you can get parts for. I am no expert, so can't say 100% on it.

Found this site at Mustangs Unlimited which has a rebuild kit for the 3-speed that may work. Got to make sure it is the fully synchronized toploader which seems to be known as the 3.03 Mustangs Unlimited - The Premier Source for Mustang, Shelby and Cougar Parts and Accessories

Found this site for Bronco's: Rebuild Kit - Manual 3 Speed, Includes Syncros, 66-77 Ford Bronco, New - Toms Bronco Parts

Found this site which now calls the transmissions "Tremec". Perhaps Tremec bought out the Ford trans line. If you look near the bottom of the page, you will see a rebuild kit for the 1968-1970 Oldsmobile 3-speed. MY bet is it could be the HD Ford Dearborn as it was used in GM cars. If not, you can inquire, who knows.

Finally, you might just search for a trans rebuild kit supplier for GM trans and inquire. If they do not list it, they may know where to get it.
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post #3 of 10 (permalink) Old 12-31-2014, 01:45 PM Thread Starter
 
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Wow thank you so much! With the info you helped with I was able to find the correct one. The odd thing is the fact that the access cover is a 9 bolt. I had to call and talk to a person on the phone before they were able to help me out. BUT I have a kit on the way and ill have a rebuilt transmission soon!!! Next is the engine! Its at the machine shop being bored/honed/cleaned and as soon as I get that puppy back ill start putting her back together!!

Chris
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post #4 of 10 (permalink) Old 12-31-2014, 07:14 PM
 
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Excellent Now you know about compression ratios for todays gas when selecting your pistons/heads, right?
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post #5 of 10 (permalink) Old 01-01-2015, 03:51 AM Thread Starter
 
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No sir, I do know they need to be changed, I just have not figured out what I need yet. Been taking this project one step at a time haha.
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post #6 of 10 (permalink) Old 01-01-2015, 08:29 AM Thread Starter
 
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I'll be honest I thought buying one of the full rebuild kits would be enough. I'll be doing some more reaserch it seems haha!
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post #7 of 10 (permalink) Old 01-01-2015, 11:03 AM
 
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I'll be honest I thought buying one of the full rebuild kits would be enough. I'll be doing some more reaserch it seems haha!
Not quite that easy. The compression is largely based on the cc's of your heads; the chamber. You can guess at it based on factory numbers which can be easily gotten off the web -but may not be accurate as heads vary and you may not know if your heads have been milled down at some point. I am using the iron 7K3 heads which are said to be 96cc's. I did some clean-up grinding/polishing in the chambers just below the intake valve. The height at which your valves seat after your valve job & the type of valve contour can effect cc's. Milling of the head can reduce cc's. So that all said, with heads assembled, my heads measured out at 98cc's.

The other measurements needed are the head gasket; thickness you are using and its bore size, not your cylinder bore size as the gasket is usually larger. Head gaskets come in different thickness. Common is .038"-.040", but can be less or more depending on what you want. My 455CI has Cometic gaskets (the best & most expensive) at .027".

Then you need to know how much area above the top of the piston at its top most travel, or top dead center (TDC) -this is often called "down in the hole". Pontiacs typically are .015"-.020". My 455CI was .020" as measured with the crank/rods/pistons fitted. This is where you will see the term "zero decked" used where the top of the block is milled to bring it level with the piston. I don't care to do this, but the real purpose is to develop a good "squish" area between the top of the piston & the head at the flat area (that part that isn't the combustion chamber) of the head that sits over the piston. The number to get is typically said to be .035", but this depends on your piston type as forged expand more than cast & rod type -aluminum rods need more clearance as they can stretch. When the piston squeezes up to the head, it pushes the gas mixture in that area into the combustion chamber & eliminates any chances for pre-ignition/knock -which is the true reason you are doing this. So you may want to go .040" - .045". With my 455CI, .020" down in the hole, forged pistons, and .027" head gaskets, I have a quench area of .047". So when everything heats up and expands, that total number will be smaller and right where I want to be.

Ok, now you have your head cc's, your head gasket cc's, and the amount of area above the piston ( bore size x .020") in cc's. The last part of the formula to determine compression will be the amount of area found in the valve relief's at the top of the piston. This is where you match your pistons to the head cc's you are using. Valve reliefs can be 6-30 cc's as a means of adjusting the compression ratio you are seeking. Of course the heads are also the way to adjust cc's by selecting a chamber with smaller or larger cc's, BUT, if you already have the heads or you have the smaller chambers, then you use the piston to dial in the desired cc's needed to get a pump friendly compression. On my 455CI I used the K-B ICON FHR forged pistons which had 10.8 cc's at the valve relief area. Taking all the numbers I had and adding them up, my compression sits at 9.02 to 1. 9.25 would have been ideal with 9.5 the max with iron heads unless you wanted to run race gas/additives. This is just where I want it for iron heads. If I had ran aluminum heads, I'd have shot for 10 minimum or 10.5 which would have probably been ideal. Compressions below 9.0 are not to be feared as they will still make your engine haul ass and be able to use low octane gas. The trick is to select a cam that raises what is called dynamic compression, which is typically the Comp Cams 110 LSA ground cams. I used the XE274 in my previous '72 400 with 7K3 heads and the replacement pistons in a rebuild kit which probably gave me 8.2 to 1 compression. Engine pulled like a train, but power dropped off like a stone at 5,500 RPM's which is a good thing for stock rods.

That compression is now used to select a camshaft designed for your engine's compression, and the max RPM you plan on spinning it under wide open fun -which is also based on the internal parts selected so you don't grenade the thing; everything has to be matched. Cam choice has other variables as well, but compression is the largest consideration in making a cam selection.

Got it?
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post #8 of 10 (permalink) Old 01-01-2015, 07:36 PM Thread Starter
 
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Hahahahaha I consider myself a intelligent person, but I have read that about 6 times and only understand half of it! I am waiting for the block to be done this week and then I'll start figuring out what parts I need and I'll do all the measurements. I'll be picking your brain to make sure that she will run on pump gas and won't blow up(I have already been in a vehicle that exploded, hence the retirement from the army!) don't want it to happen again.

Chris
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post #9 of 10 (permalink) Old 01-02-2015, 06:22 PM
 
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Hahahahaha I consider myself a intelligent person, but I have read that about 6 times and only understand half of it! I am waiting for the block to be done this week and then I'll start figuring out what parts I need and I'll do all the measurements. I'll be picking your brain to make sure that she will run on pump gas and won't blow up(I have already been in a vehicle that exploded, hence the retirement from the army!) don't want it to happen again.

Chris
I am hoping you already have your pistons??? You don't bore a block without the pistons. Pistons typically have to be fitted to the block wherein the pistons are measured and then the block is finish honed after boring to give you the correct tolerances that are recommended by the piston manufacturer. You don't want a block bored .030" over, buy your pistons, and find out you don't have enough clearance and the piston seizes in the bore or the tolerances are too large and you have a piston that can rock in the bore.

Now if you have already purchased pistons, you will then have to match the head chamber volume (cc's of the head) to work with the pistons you selected to get a streetable compression.
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post #10 of 10 (permalink) Old 01-03-2015, 11:56 AM Thread Starter
 
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Well it looks like I have my work cut out for me, I am going to set aside the engine and work on the body/paint work(which I know I can do!!) then I'll come back to the engine at the end I guess. I just want something that I can drive often and run on pump gas WITHOUT spending 5k to upgrade the engine, but if that's what I need to do so be it. I am saving a ton by doing my own body work and paint. I'll keep picking your brain and see if you guys can lay out the actual parts that I need to put into the engine on the most cost efficient level to run on pump gas. I am not concerened with the numbers or keeping it stock, I just want to enjoy the car and driving it as much as I can.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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