Dynatard

[fjh]

3 hours ago, D-Day said:

 

Good find bro!

[D-Day]

This is where the magic happens the rocker arm adjusters have 2 oil reservoirs and pistons that apply the retarding action by opening the valve on the longer profile at the rocker arm not the cam lobe when the small parts inside the rocker arm adjuster get worn that is where the problem starts with dynatard

[mackone]

O.K. thanks D-Day this helps more to understand how the dynatard works 

[mrsmackpaul]

So would it then be possible to set up a dial indicator on the exhaust push rod

Then rotate the engine slowly and see the dip in the cam lobe if it's a Dynatard cam ?

Paul 

[mrsmackpaul]

So by looking at those two pictures above 

It looks like none of the small bits have O rings to seal them up, is this correct ?

If so I  gather this means once they are worn they go in the rubbish bin

Or is there rebuild kits and how would someone check these are or are not working as they should 

I think I might have to get my workshop manual out for these, I  have looked before many years ago but I seam to recall it was pretty vague, mind the way my head has been of late it could be I just dont remember 

It would be good to have Dynatard that actually works 

I reckon reading in the advertising blerb it was like 400 hp of braking effort on the E6, might of been the E9

Either way I reckon that should still be a lot more noticeable than just making the noise 

Paul 

[MACKS]

2 hours ago, mrsmackpaul said:

So by looking at those two pictures above 

It looks like none of the small bits have O rings to seal them up, is this correct ?

If so I  gather this means once they are worn they go in the rubbish bin

Or is there rebuild kits and how would someone check these are or are not working as they should 

I think I might have to get my workshop manual out for these, I  have looked before many years ago but I seam to recall it was pretty vague, mind the way my head has been of late it could be I just dont remember 

It would be good to have Dynatard that actually works 

I reckon reading in the advertising blerb it was like 400 hp of braking effort on the E6, might of been the E9

Either way I reckon that should still be a lot more noticeable than just making the noise 

Paul 

Well keep us posted,would love to have a decent engine brake on my 96 cl,as I said it’s pretty useless as is..

[fjh]

6 hours ago, mrsmackpaul said:

So by looking at those two pictures above 

It looks like none of the small bits have O rings to seal them up, is this correct ?

If so I  gather this means once they are worn they go in the rubbish bin

Or is there rebuild kits and how would someone check these are or are not working as they should 

I think I might have to get my workshop manual out for these, I  have looked before many years ago but I seam to recall it was pretty vague, mind the way my head has been of late it could be I just dont remember 

It would be good to have Dynatard that actually works 

I reckon reading in the advertising blerb it was like 400 hp of braking effort on the E6, might of been the E9

Either way I reckon that should still be a lot more noticeable than just making the noise 

Paul 

The lash adjusters have a few  orings  i believe and one under the rockers pedestal is all used to be able to rebuild them if I remember then they were offered as complete units!  as with most things now not likley to find any these days!

[mrsmackpaul]

Well I ordered and paid for book about these today from fleabay

Hopefully I will have some added information to lead me to a positive understanding of these

Dynatard was available from 1973 in Australia according to Mack Australia 

I'll go on the hunt for some brochures or fliers I think you blokes call them as they would of had the specs listed

I think 76 was the first of the Coolpower Macks in Australia 

 

Will keep you all up to date with what I learn or dont learn

But some people, very few reckon they worked really good on a E6, most people are like me and apart from making the noise didn't do stuff all even when on full revs or higher

 

Paul

[Joey Mack]

They were weak,,  I used to try to tune them better, and my limited knowledge and resources on E-6's didn't help either..  That is a book That I need in my library..  Jojo

[theakerstwo]

I have said for years that you can get more braking from rolling the windows up and holding both doors open.But i like them better than jakes for shifting because they are faster.

[Mark T]

I should probably know better than to comment, but it's been my experience that a functioning Dynatard works as well as a Jake .    Thing ya gotta remember is back when these (both Dynatard and Jake) were in use, they were both pretty anemic as compared to anything newer. Lots of Macks back then had fairly slow axles and if downshifted there was some effect from an engine brake. (think parking a car and putting it in reverse compared to 4th on a hill)  E7 had a little more retarding power, but Macks and engine brakes never really had it until the E Tech.  E9 with a Dynatard had some power, but probably because it was much larger displacement . 

[Joey Mack]

I have often wondered if the gearing in the tranny's like 5 and 7 spd. were also a reason for the weak engine breaking? because you had to run them up to 1800+ before shifting, tells me that when you let off the throttle and reverse the torque throught the tranny, you are turning gears that are able to over come the engine power because the gear ratio's are far apart?  Of course I probably should have looked at a chart before this comment, but when I drive a 9spd plus truck and use the engine brake and downshift I would get some decent engine braking, but in a 5/7 spd Mack, I would have to wait longer to downshift to get the full advantage of the engine brake..  Of course I'm talking about Pre- Powerleash engine brakes..  Looking forward to more comments..  

[mrsmackpaul]

All I can say with any degree of accuracy is that all the comments above are about what I find

However some people claim they work good and as good a Jacobs, these are the exception rather th asn the rule

Even if I discounted over exaggeration and cut it in half and divided by four, thats still better than what I experience 

So I am after the elusive pot of unobtainium Dynatard gold that is a effective engine brake 

Is it possible, I really dont know and don't have high expectations, I will however make a video to bore you all with of my findings 😴😴

 

Paul

[fjh]

2 hours ago, Joey Mack said:

They were weak,,  I used to try to tune them better, and my limited knowledge and resources on E-6's didn't help either..  That is a book That I need in my library..  Jojo

I tried also tried sneaking in a thou or two on a valve set didn’t really help! Can’t make a silk purse from a sow’s ear !the dynatard improved some with 4 valve head but not much! Power leash improved it hugely ! Sill weak compared to Cummins ! However displacement plays a part there!

[mechohaulic]

calling them weak is being real nice. back in '73-74 i filled out more warranty paperwork. should have made up a big sign saying ==I know all they do is make noise . gets me thinking of all the "first I 've seen. == dynatards; kelsey-hayse disc brakes , one positive was the 866 v-8. . dynatards just didn't belong in same category as the jacobs (back then ). course with the dynatard you didn't have to buy 8 in exhaust stacks = they made enough noise.

[storkmack]

I have an 85’ E6 350 with a 12sp.   I was impressed with how the dynatard worked.   Using it while upshitfing, you could leave other  trucks in your dust. 

[mechohaulic]

to this day I notice many drivers using the engine brake for "speed shifting"' years back at many classes the instructors specifically stated an engine brake not mattering what manufacture should not be used for shifting.  back then a major construction co made it known to its drivers : anyone caught engine brake shifting will be terminated. seems rules must have changed. company still around bigger then ever and I hear their trucks engine brake shifting. sadly they are no longer a Mack  co. 

[BOBWhite]

I get why people speed shift but they're not usually the one's who have to pay the repair bill.

Manual transmission trucks are going away for that reason. So please, shift with care and enjoy it. To me its just as fun and rewarding. 

[Mark T]

Don't kid yourselves..... any time you can change gears and the shifter goes through your hand smooth, you're not hurting anything.  All comes down to weather you know what you're doing or not.  

[67RModel]

In a situation where you will loose road speed much faster than your engine RPMs will fall shifting on the jake can be beneficial if you know what your doing. Is it necessary? Maybe, maybe not. Plus whos to say the automated manuals aren't designed to do this anyway? There is a reason they never miss a gear heavily loaded on a steep grade starting from a dead stop. I think where its gets ridiculous is when you see guys empty on level ground shifting and splitting every gear on the jake. Maybe they just like to hear that noise from their straight pipes. 

Edited February 20, 2023 by 67RModel

[mechohaulic]

fully agree with Mark T and 67RModel.  shifting with the engine brake is a positive "if you know what your doing" and it is needed. and the ridiculous  is a sure thing when as stated "level empty jaking every (unnecessary ) gear to hear the 8 in pipes Beller. put the speed shifters behind a quad ; watch how fast speed shifting takes place. LOL at least the 4in  pipes would sound better then the 8 in. quess i just can't leave the 50's -60's- 70's trucking .  b-models weren't 250K , didn't have 100 lights on alum bodys. lest us NOT go off topic .

[mrsmackpaul]

1 hour ago, mechohaulic said:

 lest us NOT go off topic .

Like that's gunna stop us from going off topic 😗😁

 

 

Paul 

[Swishy]

the early maxidynes with a 5 speed relied on a good clutch brake to kill revs Btween gears

the next V: they used the engine brake to kill the revs and do a quik shift. U could pull the gear lever stright thru ,It twas the next best thing to a automatic

U did half the gear changes compared to a screemer /road ranger set up

The late 60's we fitted jake brakes to B61 mack with Quadbox ....most effective in saving brakes as most Lowboys of th@ era had air over Hyd brakes

thinkn way back wen Engine brakes produced ruffly 90% of retardation power of the engine HP

rule of thumb twas wot ever gear U pull a load/hill U could go down the hill with the same load & gear with only lightly fannin the brakes to control the rev speedmy tax my taz free info for the day

LOL

cya

 

[mackone]

Hello,  I bought this service manual on ebay , and according to this it looks like all engines have the dynatard cam in the E6's, just giving an update,  thanks to everyone for posting and helping.

 

[Joey Mack]

I have that book too..  Damn good one to have..   Jojo