1985 C-6 truck tranny, no engine braking effect - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-03-2008, 12:12 PM
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1985 C-6 truck tranny, no engine braking effect

ok i have been trying to get a straight answer on this and not having much luck

i have a 1985 f250 pickup with the HO 351W 4bbl and it has the c-6 trans in it

now it runs strong and smooth and drives fine

however i notice that when cruising down the road when you let off the gas pedal the idle returns to idle speed and had no engine braking effect at all, zero, none, nothing

now i have noticed many other old c-6 trucks that do the same exact thing

so i always have assumed it was a normal ford thing


i know jack crap about ford auto trannies, they are the wierdest freaking thing out there short of maybe dark matter

with their crazy linkage parts and oddball rod and so on


i am a GM type guy i have always driven GM products except for a couple old ford truck i had in the past but they were 3 speed manual trans ones

GM trannies always have tons of engine braking effect

and its great, it saves your *** when your brakes fail, as they did on this truck when i got it(rear wheel cylinder blown), i had to drive up on someones yard ot stop the truck because shutting it off in gear does nothing whatsoever, unlike with a GM tranny, this C-6 trans allows the truck to roll forever and ever, zero resistance, its insane., and scary! i thought i was a gonner when i luckily got it stopped at the crest of the hill it was about to take me down



we do have a '77 F-150 4x4 with a c-6 in it but we never drive it on the road, i have in the past but never noticed if it has any braking effect

i cant recall

it is restored and all new inside and out and we are doing a few things to it and then selling it soon to put the $ into restoring the '82 K-10 S/F

if the C-6 trans are supposed ot have engine braking effect then what might the problem be with all these old c-6's that dont have any ?

my truck has an edelbrock 1406 on it, maybe the kickdown not being adjusted or connected is why ?

also i found that the truck will not pull the car trailer loaded down to a total weight of about 8k lbs

it barely would move it, just sat there

but it drives fine empty, plenty strong

so i am really confused here

need info

if the trans is junk then i need to take the truck to the shredder soon

i really dont know what would be worth saving off a 351 4bbl truck, power steering pump parts, brackets ? a/c ? anything ? mounts ? distrib ? module ? EEC ? radiator ? everything is good and runs excellent



thanks for anything

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Last edited by fast68; 01-03-2008 at 12:21 PM.
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Old 01-03-2008, 01:22 PM
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I am not a tranny expert but I remember my father bought a new 79 Lincoln and that was one of the features advertised.So I guess it is possible they did it on some trucks too.
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Old 01-03-2008, 01:46 PM
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oh wow thats interesting hmmm

anyone know any more on this ?


thanks
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Old 01-03-2008, 03:09 PM
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c-6

I would imagine you have a high final drive ratio in this vehicle, that would mean a low numerical gear, and this is why you feel no engine braking, on coast.
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Old 01-03-2008, 09:29 PM
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it is 3.50

trus tme i know all about axle ratios and final drive ratios and torque multiplication and so on


this is a heavy 3/4 ton with full floating rear, 10.25" axle

8600 gvcw

it sits up real high in stock form


dont know why you would think it has highway ratio in it

even chevies ran no higher ratio than 3.73 except some rare 3.23 ones

and commonly ran 4.10 and 4.56

even through the 80s

20 and 30 series

(8 lug)

such as this truck is



does anyone have a definite answer

is my tranny acting right or not


please help!

?


should it have any braking effect or not ?!

it has NONE

ZERO

complete and total free coast

the most you could possibly have

i have owned and driven billions of trucks over the years, of all series, ford and gm both, from 1/2 tons to 2 tons(c-60 trucks yes)

i know what gm trannies act like and what engine trans braking effect is ok

this ford has NONE!

it acts like it is totally disconnected from the engine when you are driving down the road and let off the gas pedal completely


no resistance whatsoever, totally free rolling, if you didnt have brakes then you would be totally screwed and would roll forever and ever

the engine returns to idle, completely, totally

as do all the ford trucks i have been in or driven in the past -and that also ran fine, like mine does


does anyone here know anything about c-6 trannies ?

i tried the ford trucks specific site and had no luck, and gave up on trying there, i was having the same problem as i am starting to have here,


has anyone here ever driven a GM auto trans equipped truck ?

you knwo how they have lots of engine braking effect ? it is very quite noticeable and different axle ratios really make no difference in how muh of this effect there is

if you have driven many different makes and models and type sof gm vehicles with auto trannies then you will know this very well. they all have this effect, and it is very pronounced




now, compare this effect to what a C-6 ford transSHOULD or should NOT have


and tell me

i need to know so i can know if i need to junk this truck or not

and by monday

monday is when i am hauling in vehicles to the shredder

i dont want ot junk it if these old ford C-6 trannies are known to have zero engine braking effect in final gear

if they are supposed to then what would cause it?


anything external and minor ?

if not, then bye bye truck

this should be very simple

yes or no, really



it never ceases to amaze me how difficult it is to find out very simple answers on the internet sometimes

wow!

:O



help ?

thanks!!

Last edited by fast68; 01-03-2008 at 09:44 PM.
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Old 01-03-2008, 10:48 PM
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re: 1985 C-6 truck tranny, no engine braking effect

are you sure its a c-6? and not a AOD?
Will it lock back up if you gas it? if it does then the linkage you said that was not hooked up my be the problem. I ran across a car that had this problem and the trouble was in the torque converter( had a electric lock up switch that was bad) but a c-6 doesn't have this.
Check these items and run a new post and let me know what you find.
Later
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Old 01-03-2008, 10:58 PM
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Quote:
also i found that the truck will not pull the car trailer loaded down to a total weight of about 8k lbs

it barely would move it, just sat there
Do you mean the engine rev'd but the transmission would not engage fully?
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Old 01-03-2008, 11:00 PM
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Its not worth it to junk out a truck because it free wheels.A lot of it probabally has to do with the gears. Does it not have a daul master cylinder?As a busted wheelcylinder should not cause total loss of brakes.Just really crappy stopping due to front brakes only.
Shane
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Old 01-04-2008, 10:15 AM
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C-6

Here is your definite answer. You should feel no engine braking in high gear.

There is no component in the C-6 transmission that will cause engine braking in high gear. Does not matter if your passing gear mechanism is operating or not.

In first gear, if you reach a speed of say 10 mph and you let off of the gas you will feel engine braking because at that speed the low reverse sprag will not overrun and will be holding the rear planetary stationary, in the drive position. Your transmission will be in reduction.

In manual low, the low reverse clutchs will be applied and this will cause the same effect.

You will feel engine braking in 2nd gear as well, the forward clutch will be applied, the band will be applied thus holding the high gear clutch drum,input shell and sun gear stationary. The front planetary unit ring gear is locked to the input shaft. The transmission will be in reduction.

In high gear the forward clutchs, direct[high gear] clutchs are both applied, all of the planetary gears and gear members are locked to each other and locked to the output shaft. This will give the transmission a 1 to 1 ratio.

At that point whatever your differential ratio is, will be the final drive ratio.

So at say 60 mph, in high gear, if you were to let off of the gas pedal, the rear would then begin to drive the trans and engine as well thus creating drag.

A high numerical differential would have a greater impact on the amount of drag or resistance you feel.

Tire size is also a variable. Other variables as well.

Hopefully you can read thru this, have it make sense to you and feel comfortable knowing that what you are feeling is normal for this vehicle.

One other thing, take a moment and read back thru what you have written in your pursuit of an answer. Take notice of your acidic method for achieving answers for your questions.

I think that if you are introspective you will come to the same conclusion that I did, you are fortunate to have anybody reply to your post.
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Old 01-27-2008, 03:28 AM
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solved the problem!

traded the truck off for a smooth running driving 92 bonneville SE 3800 4L60E

title for title swap


yay

a week ago even

thanks!
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Old 01-27-2008, 10:09 AM
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Whoever commented on no engine braking is supplying erroneous info. I can't comment specifcly on later ones, although I never read or noticed any real inner changes. I run C6 trannies in several vehicles...they all have engine braking. I would suggest, I know you have traded it, anyone that has a non engine braking C6, there is a problem. It may be the Torque convertor sprag is defective or bands slipping, clutch pack worn...but it is not right. Have it checked out before you're left stranded. As for the gear ratio comment,the steeper the gear( lower numerically) the less it will brake, the lower (higher numerically) the MORE it should, not the reverse. Ask any drag racer about it when they decelerate, the lower ratio is effectively attempting to turn the engine more rpms because of it.
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Old 01-27-2008, 10:41 AM
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Woods428, I am not a tranny expert and I don't know if you are but my info is not wrong. My father bought a new 1979 Lincoln and it specifically stated that this was an option on his car. I don't know where to find it in writing and I am sure it is not on all trannys but it was correct on this one.Sorry he died and does not have the car anymore,but we read it together and I remember it well because I had never heard of such a thing before.
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Old 01-27-2008, 10:51 AM
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good info and i am still willing ot learn about this phenomenom regarding the c-6 braking effect

i hate to see anyone argue in Re of it though

just is something that was bugging me about the truck and is something i have seen occur in past c-6 trannies

so i always assumed that c-6 trannies didnt have any or much braking effect

i have been in and driven many different automatic trans old ford cars and trucks over the years but cannot recall if any had engine brake effector not now, its been too long now, hmm
i seem to never pay attention to it when i need to, but the 85 F250 definitely had ZERo brake effect FOR SURE, was always a total and completely free coast and engine idle speed rpm when you let off the accelerator pedal as if it were in neutral, even though it wasnt


maybe we will never know for sure

hmm

ill see if i can tak the 77 f150 4x4 with the c-6 in it out for a spin again soon and see if it has a braking effect, because i have forgotten since the lat time i got to drive it out and around, it is not plated right now and we are cleaning it up to sell it it is mostly restored, new interior, newer paint, new engine bearings and rings and rebuilt heads(i assembled the engine personally and it runs STRONG 351 2v cleveland), brand new shocks, brand new centerlink, brand new tires, and so on

so..


thanks for the info!


Last edited by fast68; 01-27-2008 at 10:56 AM.
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Old 01-27-2008, 02:14 PM
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Quote:
Originally Posted by speedydeedy
Woods428, I am not a tranny expert and I don't know if you are but my info is not wrong. My father bought a new 1979 Lincoln and it specifically stated that this was an option on his car. I don't know where to find it in writing and I am sure it is not on all trannys but it was correct on this one.Sorry he died and does not have the car anymore,but we read it together and I remember it well because I had never heard of such a thing before.
As I said, I can't be certain about later trannies, but I know the early ones well..there is braking. I have all the factory tech stuff from that period and will check up on the Lincoln deal. Many times Lincoln offered stuff as an experiment that didn't get perpetuated further, this may be one, I'll check out what the factory says. I know I have ridden in trucks later than '79 that had engine braking, if it was an option, that wouldn't make it typical .
Before I went out and looked at my books, I figured I'd Google C6 as well Freewheeling C6, there was no mention of anything to do with free wheeling. It did mention here http://www.answers.com/topic/ford-c6-transmission that 1979 was the last year a C6 was used in a Lincoln..food for thought. Free wheeling has been around for ages though, it was used early on with the SAAB, but was dropped when they started importing more to the U.S. for safety reasons...no engine braking.. besides my C6 experience that's another reason I'm sceptical. They were also controlable, being able to engage or disengage the feature.. you make no mention of that control.

Last edited by woodz428; 01-27-2008 at 02:27 PM.
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Old 01-27-2008, 02:51 PM
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I strive to give accurate info on this an all the websites that I supply Tech info on, and if I am questioned I have an enormous library of resources that I can check out anything that I may be uncertain of. I have just examined the 1979 Ford factory manual, several automatic transmission books and an interchange manual. I found out what I believed is true..there was NO freewheeling C6 transmission plain and simple. The interchange listed the contol lever as the only difference between the C6 trans that fit behind the Lincoln of that year and all others before it. So Speedy, without some type of authentication I would have to say that , once again, that information is false. Anyone reading this should take it as false, unless you can provide some documentation of such a thing. I stand by my original post ...IF it is a C6, it DOES have engine braking unless something is amiss. I believe that the 1985 probably was an AOD and wasn't the C6 he thought. The AOD was phased in for SBs by then and only the monster (460) engines received the C6.
I am always open to new information, so if you can supply some proof,other than " I remember", I'll be glad to change my position. Having rebuilt several, I find it odd that I have never come across this info in any publication or parts books. This is my living, not just a hobby, so I am always wanting as much info as I can get.. I also specialize in Fords..so once again..IF true, would like to add that to my memory banks.
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