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'66 Classic - throttle valve and band adjustments?

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RamblerClassic66 View Drop Down
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    Posted: Nov/26/2008 at 9:17am
Ok, the transmission in my Classic was recently rebuilt, and it needs band adjustments, as well as probably the throttle valve cable also. I am not sure how to do it, as I haven't experienced it yet. I do have a 66-73 Chilton's that explains it (band adjustment), but I want to make sure it's the right directions for my automatic. I'll go ahead and type up what the Chilton's says. It's the Borg Warner "Flash-O-Matic" M-4x three speed automatic. Any help is appreciated. Thanks!

Front Band - 1966-71
1. Drain transmission fluid, remove oil pan.
2. Check for debris, scorched fluid, etc.
3. Check pickup screen for clogging, make sure all parts snug, etc.
Then it says To adjust, insert a 1/4" gauge block between the front servo, adjusting screw, and the piston rod, then tighten adjusting screw to 9 in. lbs. Then put pan back on with new gasket, and put proper amount of fluid back in.

Rear Band - Place a jack under the transmission, then remove the crossmember.
2. Lower the transmission then loosen the rear band adjusting screw locknut, and tighten the screw to 10 ft. lbs for 66 and later.
3. Back off adjusting screw 3/4 turn for the M36, M37, m40, M43, and M44, then tighten locknut to 28 ft. lbs. Reinstall crossmember.
'97 Cadillac Catera
'03 Durango SXT - 4.7 Magnum V8
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2008 at 7:35am
For starters, you don't have a M-40 if it's the original trans. Sounds like you may have a different year engine/trans combo if the carb is a Holley 1920 as you stated in another post. Verify what model trans you have. On the passenger side of the trans case, near where the shift lever comes out, is a plate. Clean it off real good and you should find a screen printed number on the lower left. It will be something like AS2-40 or AS8-11. The last two numbers are the model. If your trans is air cooled -- has a large hole in the right side of the bell housing -- it's a M-35, 36, or 37. One of those were usually used in the mid 60s cars. FYI, the "3" is 30 series, the second number is a reference to how much torque the trans will handle -- larger number, more torque. I don't think the numbers mean any specific amount, just more than the one lower.

The throttle valve cable is very important! NEVER run the car without it! It works the same as the TV cable on an early model GM 700R4, it controls internal trans pressure. At idle pressure is low, and at low speed so shifts aren't harsh. As speed goes up more pressure is needed to hold the clutches and bands. When the cable "bottoms out" and the car isn't going over a certain speed (around 60), the trans will kick down into second gear ("passing gear").

I just discovered a missing paragraph in the 66 TSM -- something that's in all previous TSMs. On page 19 of the 66 TSM (Flash-O-Matic, 232 section), under "Transmission Oil Pressure, Inspection and Adjustment", there is no preliminary adjustment for the cable. You would have to use a pressure gauge. In the 65 TSM, page 15 (Flash-O-Matic, 199/232 section) there is the adjustment procedure I've used for years on M-3x and early M-8 trannys -- Disconnect the TV cable at the throttle linkage. Adjust the clevis to a "free Pin" fit (the pin will easily slide in and out without moving the cable or linkage, or as close to that as possible), then adjust hte cable two full turns longer. You can go another full turn to get a little harder shift, but remember that the trans will kick-down a bit sooner. I'd not go more than one full turn longer, or shorter. Ideally you would use a pressure gauge as the 66 (and 65) TSM says, but that's not something the average guy will have. Using the length as specified has always worked for me over the last 20 years. I usually drive the car a few days at the specified length (two turns longer than "lose pin fit") then play with it a little if I want harder shifts, usually adjust 1/2 tunr to one turn long. I found that downshifts were way too often/soon with the cable two turns long, it would downshift holding cruising speed up hills, something you don't want! Too short and the trans shifts real soft and slips more, which leads to accelerated wear. The cable should be easy to push and pull holding the clevis between tow fingers. If you need pliers or it doesn't move easily when the throttle is pressed the cable needs to come out and be cleaned and lubed. It's not a tough job, but it takes some time! If the cable doesn't move freely you will eventually burn up the trans from inadequate pressure.

In general, the instructions you listed are correct. If the builder is close by I'd take it to the shop for an adjustment. They don't usually need adjusting after rebuilding, but there could be some stretching or wearing of the bands when breaking in.

You can lower the trans and just stick a torque wrench on it and use those torque specs.
Note that a special extension tool is shown in the TSM to adjust the rear band without lowering the trans. The length of the tool affects the torque readings. The 66 TSM (and 65) gives the formula on page 40 of the Flash-O-Matic section.

If you plan on doing work like this on the car you almost HAVE to have a factory service manual (Technical Service Manual, or TSM). It's geared toward someone who has general mechanic knowledge, but thoroughly explains things that are unique to that car. The TSMs don't cost that much, you can find them on e-bay all the time for under $40. It will save a lot more than that just for one or two repairs. See e-bay item number 130270783040. A 65 manual will serve you just as well, there are only a few cosmetic changes between 65 and 66. Make sure it's NOT an "American" manual, of course!
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RamblerClassic66 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2008 at 8:41am
Hmm... Amcyclopedia says -

Borg Warner "Flash-O-Matic" T-35 three speed automatic, air cooled torque converter, cable operated throttle valve; 195.6 only

Borg Warner "Flash-O-Matic" M-4x three speed automatic, water/oil cooled, cable operated throttle valve; all six cylinders except 195.6

Borg Warner "Flash-O-Matic" M-10 three speed automatic, water/oil cooled, cable operated throttle valve; V-8 only

But I will go check right now to see what it is. Amcyclopedia may be wrong.
'97 Cadillac Catera
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RamblerClassic66 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2008 at 12:35pm
Well, this is odd. It has the large cooling holes, and is definitely not water or oil cooled. So, apparently it's the T-3x.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2008 at 4:31pm
That's what I thought. There are some errors in the AMCyclopedia list. The glaring one is the "M-10". There is no such animal! Before the M-11 and M-12 was the M-8. But that's no big deal, all iron BWs before 67 were the same. There's only one minor variation -- the 65-66 M-8 has both vacuum and cable controlled pressure sensing. The vacuum line doesn't go to a modulator, but does connect to a valve of some sort internal to the trans. It's more of a reference signal I think. That one really confuses people! Before then the iron M-8 used a vacuum modulator and only the M-3x used the cable. The 67 model M-11 uses a vacuum modulator also. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RamblerClassic66 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2008 at 7:52am
Wow, that cable was TOTALLY adjusted wrong. But my question now is, do you adjust the clevis with the cable extended out, or pushed in?

Hopefully someone responds, I have to leave for work in 2 hours. LOL.
'97 Cadillac Catera
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2008 at 3:50pm
You adjust the cable with the throttle linkage at idle position, which is pulled out. The cable pushes in as the gas pedal goes down (throttle opens). 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RamblerClassic66 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2008 at 8:04pm
That's what I thought. It was actually bass ackwards and fixed the shifting problem, but I still have to adjust the bands. Now on to more carb tuning, intake manifold gasket change (I think its leaking) and Pertronix conversion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2008 at 7:01am
If it shifts good now, with very little or no slipping, you should be okay without adjusting the bands. Check the trans fluid and smell it. If it has a slightly burned smell to it change it and adjust the bands. You have to drop the pan and change the fluid to adjust the front band anyway.

If the fluid isn't "burnt" the bands probably don't need to be adjusted, though it can't hurt (unless you get them too tight or loose). The fluid doesn't actually burn, the bands and clutches "burn" from slipping more than they should, and contaminate the fluid. The bands/clutches are supposed to slip a little between gears to smooth out shifts, but shouldn't slip so much as to burn. 

Edited by farna - Dec/01/2008 at 9:23am
Frank Swygert
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