Transmission Question

[4eyed83]

I currently have a C4 in my little 83 coupe and I am trying to research my options with no luck. I am thinking of just preforming a good rebuild on the C4 but hate the gear ratios for the C4, is there different gear sets for the C4 available? I was also thinking of a AOD but I really don't want to screw around with the TV cable, who has done an AOD and is it reliable?

TIA
Jason

[mustangxtreme]

I run one behind a 5.0 and haven't had any issues. I do appreciate the increase in mileage I get from having an od.

[xctasy]

Back in the day(1977) , behind a modfied 130 hp 4-bbl equiped 2 liter Pinto, that worked T bar C4's lost 8 to 12 hp at the rear wheels more than a stick shifted transmission on.

That verified the 1.264 for manual verses almost 1.45 for auto drive train loss the chassis dynamometer shows everytime an auto is compared to a stick shift. At the stout SBF level, with 390 hp flywheel net level, thats a 24 to 36 hp loss, on a pro rata basis, almost equal to the loss of 45 cubic inches, making a 347 behave like a 302, or a 302, a 262.

The only remediating factor is


1. the auto is strong, and won't blow up like a T5 can,

2. and traction is safer off the mark,

3. and the unmatchable urge under kickdown that catches many stick shifts out on the unanounced overtaking.

The torque convert might be the reason US automakes have had to push so hard for fuel economy, because it acts like a 15% Goods and Services tax on horspwer, torque and miles per gallon.


There is a "poor mans overdrive" kit that widens the C4 ratio spread from 2.46 to 2.92 or 2.75 from Summit creates a make belive OD 3RD with an 0.89 or 0.84:1 over drive. Esentially like the " The Court Room To The Race Track" 3 speed 200THM used from 1976 to the early 80's.

When done in conjuction with a rebuild, its a cheap option. This was done often in the 70's with some C4'S...before people became confident in the AOD and 4W70R.



The wider ratio step alows you to move numerically down 0.89-.0.84.


So
4.10 gears--->3.55
3.90 gears--->3.38
3.73 gears--->3.23
3.55 gears--->3.08
3.45 gears--->3.00
3.27 gears--->2.83

The AOD/OD-E were much tougher nuts to crack, but give exceptional results if you use the hybridised Toyota style Over Drive buttoned lockout with the SilverFox valve body and perhaps the wide ratio 4W70R gearset without electronic control.

Much error ridden info has been bandied about over the AOD TV cable. The AOD TV cable is effectively the ages old 1957 to 1972 Borg Warner 35/40/42 series design (think Rambler American L head 194, 232 or 256, or AMC Rebel 304 or perhaps 343. Its operation back then screwed many a good slush box, but since the port EFI era, it has been debugged with proper set up via the fuel pressure gage into the hydraulic port. The 4bbl carb sales of Edlebrock carbs forced the aftermarket to develope the same kind of 0.265" curb idle spacer Ford used, and it is used to get the line pressure in ball park, and the peak pullout just has to be 1.75" or so, with the throttle not being resricted in any way by the TV cable. Depending on carb or EFI throttle linkage type, and upshift RPM, there are three different sizes to dial the TV cable in.

Guys in the Southern Hemsphere have been doing that since 1965 with Ford Falcons and Volvo 144/164/240/260's, eraly Cortinas before 1972, all Jag XJ6's and Rover 3500's...its a pretty simple system. The Edelbrock and Holley 4-bbls now have bolt on high or low mount clip on kits to copy the factrory Ford cable or rod kickdown "Throttle Valve".

Normally, the aftermarket kits dispense with the TV system, (no-one has really gotten used to it when you consider how simple the C4/C6 kickdown is) and move back to the constant pressure kickdown via a Lockar 24" cable, but lower tier AOD modifications can still work fine with the stock TV system. I love the system, always have, but I got taught by guys who raced 205 hp Chrysler Valiant Charger race cars from 1971 to 1982, winning every race for 11 years with a busted a$$ gearbox circa 1957 designed for a 90 hp 195.6 L head six. The mantra was alllways

" 5/16" at curb idle,
line pressue set with fuel pressure gage,
and 1-3/4" maxiumm pullout".


In a similar manner, people rabbit on about the inability of a potential 1st, 2nd and 3rd gear 500- to 700 hp strength which is then lost when the AOD drops into 4th....well, that's true of most over drives, and the issue is only what kind of lockup do you want in 4th, the weird a$$ stock set up input shaft which takes on a macorini or spagetti section when overloaded, or a unlocked 300M shaft which uses the C6 torque converter, or a hybrid lock-up 4W70R system.

I'd plug for a stock three element O/D top, keep the overdrive, and use the factory 39A et al 2350 rpm stall 2.53:1 converter. Over drive should only ever be a light load situation gear, if you want full throttle upshifts into 4th at the drags, you'd be better off with spending the U$2500 for a GearVendors 0.78:1 overdrive system. No overdrive is full proof. The 4R70W overdrive is tougher, but you then have to consider if your going to lock-up the clutch.

Again, the 4R70W is fully electronic, and needs a liitle more space because of its case length, and a TPS and handshaked link to allow the electronic gearbox controoler to work.

The stock intermediate ratios are FMX ratios for the AOD, unless its had the 4R70W parts grafted in. For Fox frames, they can probably enjoy the wide ratio gearset from the later gearbox. Its all down to how well a live axled coil sprung race car can hook up. On the street, any automatic will loose a lot of offline power verses a T5.


Back in the day, behind a worked T bar C4's lost 8 to 12 hp at the rear wheels more than a stick shifted transmission on a modfied 130 hp 4-bbl equiped 2 liter Pinto. That verified the 1.264 for manual verses 1.45 for auto drive train loss the chassis dynamometer shows everytime an auto is compared to a stick shift. And at the 390 hp flywheel net level, thats a 24 to 36 hp loss, equal to the loss of 45 cubic inches, making a 347 behave like a 302, or a 302, a 262.

[KevinVarnes]

The TV cable isn't anything to be afraid of. If you did convert to AOD you would need to procure the cable, a bracket to mount the cable, and most likely a linkage geometry corrector bracket (I am assuming you have a carb). I have an AOD in my '91 Crown Vic. The car originally came with the 2-bbl variable venturi carb, but I've since replaced that with a Holley 4-bbl. I am using the original TV cable and bracket. I originally took the TV cable attachment bracket from the VV carb linkage and welded it onto the Holley linkage. A few years later I was getting leaks on the secondary throttle shaft bushings so I replaced the base plate and just ordered a geometry corrector bracket to get the proper cable travel. https://www.summitracing.com/search/...ssion-type/aod
Very easy to set up.

[Haystack]

Setting the aod reslly isnt critical. What kills them is when the tv cable falls off. I had an 88 crown vic. The wife took it to the gas station 1/2 mile down the road, not even gone 5 minutes. I didnt egen make it out of the parking lot before i knew something was wrong. Popped the hood and sure enough. It hesitated and slipped in od from that day forwards.

Ive had other cars go well past 200k miles without issue, and i beat the crap out of my cars.

Personally, id just go t-5. They are plentiful and cheap, a full swap can be done for less then $400 if you are careful, and sn-95 v-6 t-5s are everywhere in the u pull it yards. If it dies, $80-150 and you are back on the road with about an hours work. Takes longer then that to add fluid and get it to the proper level in an aod.

[4eyed83]

Yall gave same great information!!! I would love to stay with an automatic just for ease of use and a bit more consistent at the track when I can make it there. If I do a manual it will be a Astro A-5 or a G-Force. I will be building up a decent little 331 and need a good trans.