Dynaflow rebuilt. clutch discs and plates question! Help please

[Selim]

Rebuilding my 1955 Buick century dynaflow 

My mechanic found 5 of CLUTCH DISCS and 5 steel clutch plates in picture bellow in my car , while there is 6 new ones of each in the rebuilding kit I got from fusick . Also the thickness of the new ones are different from old ones. How many should b there? new ones are thinner than old ones. my mechanic is suggesting that we use 6 steel plates with 5 clutch discs inbetween . but my question is why there is a different in numbers and thickness between old and new ones? 

Edited December 14, 2020 by Selim (see edit history)

[old-tank]

You should probably ask the supplier.

1955 used 5 pairs; 56 used 6 pairs, so maybe the "kit" was for multiple years?

How much difference in a stack of 5 of the old vs new?  Note that the clutch friction discs will swell somewhat when soaked in transmission fluid.

You should probably ask the supplier.

 

[Selim]

actually my car had 5 pairs but indeed the clutch discs thickness is different probably due to the fact that they are not swollen yet by transmission fluid! but when we put 5 pairs in their place they are not fitting fully! there is a gap of almost 1.5 mm. my mechanic is suggesting putting 6 steel plates and 5 clutch discs in-between cos with this stack they are fitted correctly in their cylinder box! should i put 5 pairs as were in the car counting on the fact that they will be swollen later or go with 6 steel+ 5 discs in-between? thanks

[old-tank]

A lot of work for "trial and error".

On my 55 we missed the fact that in the past someone had substituted a 56 clutch drum for the 55 into which we installed 5 pairs.  It tried to move in drive with much slippage.  Installed 6 pairs with good results.

[Selim]

Attached are photos when I use 5 pairs and 6 pairs

you can see that with 6 pairs they reach the top limit while with 5 pairs they are less by 1,5 mm

should I use 5 or 6 pairs?

[Selim]

4 minutes ago, Selim said:

Attached are photos when I use 5 pairs and 6 pairs

you can see that with 6 pairs they reach the top limit while with 5 pairs they are less by 1,5 mm

should I use 5 or 6 pairs?

 

[avgwarhawk]

Willie suggest 6 pairs. He had a 56 clutch pack in his 55.  Perhaps some changed over to the larger clutch pack when rebuilding for better performance? Maybe that is the case with your transmission.   

[avgwarhawk]

This may help:

 

 

[JohnD1956]

Unless I missed something, Mudbones video clearly shows the first ring removed was a clutch, not a steel band.  And if you had five clutches and 5 bands then I would think it incorrect to install 5 clutches and six bands.  As for what the depth should be, what does the service manual say?

[avgwarhawk]

17 minutes ago, JohnD1956 said:

Unless I missed something, Mudbones video clearly shows the first ring removed was a clutch, not a steel band.  And if you had five clutches and 5 bands then I would think it incorrect to install 5 clutches and six bands.  As for what the depth should be, what does the service manual say?

 

It appears to end with a clutch as well.  So 5 clutches and 4 bands was I watch the video.   

 

Hopefully Mudbone will be along to advise. 

[Selim]

My mechanic suggesting 6 steel and 5 band clutch in order to fit in like pic

is that correct? 
or there should be a bit of space inside ? In that case I d use 5+5 but there will be more space that mechanic is not feeling comfortable with. He is not Buick expert though 

[Selim]

Just now, Selim said:

My mechanic suggesting 6 steel and 5 band clutch in order to fit in like pic

is that correct? 
or there should be a bit of space inside ? In that case I d use 5+5 but there will be more space that mechanic is not feeling comfortable with. He is not Buick expert though 

Here is with space if I use 5+5

is that correct?

[avgwarhawk]

Look here:

 

https://www.hometownbuick.com/1955-buick-dynaflow-removal-installation/

 

 

 

[TexasJohn55]

You are not considering that there is a clearance spec on clutch pack. The clutch has to be assembled. If you have too many discs, you will not be able to assemble unit and install the 3 wedges and snap ring. You must be able to wiggle the clutch discs after assembled. Don't forget, all the steels are waved and must be installed facing the same direction. Refer to the shop manual pages 189,190 and 191 or 5-49,5-50 and 5-51. It is obvious that you will have to use 5 and 5 in the order the shop manual designates, you cannot add an extra steel, that would put steel to steel when engaging.

[Selim]

my mechanic understood that manual suggesting 5+5 but he reached the conclusion that he will add one extra steel clutch plate on top of the last steel plate (double on top of each other) to compensate difference in thickness with old ones. so the tranny will have 6 steel plates with 5 clutch discs. is that ok?

[Selim]

On 12/14/2020 at 8:36 AM, avgwarhawk said:

Willie suggest 6 pairs. He had a 56 clutch pack in his 55.  Perhaps some changed over to the larger clutch pack when rebuilding for better performance? Maybe that is the case with your transmission.   

my mechanic understood that manual suggesting 5+5 but he reached the conclusion that he will add one extra steel clutch plate on top of the last steel plate (double on top of each other) to compensate difference in thickness with old ones. so the tranny will have 6 steel plates with 5 clutch discs. is that ok?

[avgwarhawk]

I would follow the repair manual. 

[Selim]

i told mechanic to follow manual as well

[Bloo]

This advice is NOT Dynaflow specific but...

 

What matters in a multiple disc automatic transmission clutch is the end clearance under the snap ring when you put it all together. If it is too loose it might not hold (slip), if too tight there could be catastrophic mechanical failure when it does not release fully. Additionally, in (non-Dynaflow) transmissions that shift under power, it affects the timing of the clutch.

 

Asking how many plates go in is sort of like asking how long is a piece of string. The plates may not be exactly the same thickness as the original. The error multiplies as you stack plates. The end clearance when assembled is what matters. There will be an acceptable range and the shop manual should tell you what it is. If you need to throw an extra steel in at one end of the pack to get the end clearance right, do it.  That is standard procedure.

 

Old steels can be re-used if they are not warped, overheated or damaged. The shop manual should tell you how to check them. They were usually re-used if good back in the day. Sand a crosshatch on them with fine paper (then clean them really well) if you re-use them. They might be a little thinner and help you hit the end clearance spec if it isn't happening with the new parts.

 

End clearance is what matters.

 

If the shop manual contradicts anything I have typed here, follow the shop manual.

 

 

 

Edited December 15, 2020 by Bloo (see edit history)

[Selim]

old stack (5+5) clearance is about 4 mm 

new set (5+5) clearance is about 4,5 mm   the new ones are a bit thinner than old od ones so clearance is more with new ones and that is worrying 4 my mechanic. that is why he wanted to use 6 steel + 5 clutch discs

[Selim]

17 hours ago, TexasJohn55 said:

You are not considering that there is a clearance spec on clutch pack. The clutch has to be assembled. If you have too many discs, you will not be able to assemble unit and install the 3 wedges and snap ring. You must be able to wiggle the clutch discs after assembled. Don't forget, all the steels are waved and must be installed facing the same direction. Refer to the shop manual pages 189,190 and 191 or 5-49,5-50 and 5-51. It is obvious that you will have to use 5 and 5 in the order the shop manual designates, you cannot add an extra steel, that would put steel to steel when engaging.

indeed with 6 that would put steel to steel. what is the problem of having steel to steel? thanks

[TexasJohn55]

Steel to steel is ok when keyed the same, they spin together.  I doubt you can add a steel and still assemble it to install the 3 wedges and snap ring, the stack will be too thick. If by some miracle you get it assembled, will it have operating clearance for clutches? They must be loose without dragging.  ( And then you think the new clutches will grow, how much?)

Edited December 15, 2020 by TexasJohn55 (see edit history)

[TexasJohn55]

Go with 5 and 5 and stop worrying about it. The piston will take up the extra travel in a nanosecond.

[Bloo]

Doesn't the shop manual have an acceptable range for end clearance? IMHO make it meet the spec in the shop manual, whatever that takes. If you are worried about expanding linings, soak them in ATF overnight. It's a good idea to do that anyway.

 

 

Edited December 16, 2020 by Bloo (see edit history)

[NTX5467]

It seems that almost EVERY, or at least MANY, automatic tranmsmission mechanics seem to know some trick or something that is supposed to work and make things work better.  Sometimes, from trusted mentors, sometimes from trial/error, and sometimes from heresay.  In ALL CASES, the factory service literature should be the DEFAULT mode UNLESS they are especially versed in "DynaFlow-ology".  Which also means what changed with each model year and knowing what one is looking at when they see it.  That's been my observations over the decades of my being around cars and people who work on them, no more no less.

From what's been mentioned, the rebuild kits are MULTI-YEAR. 

 

Match what came out of your clutch packs, period.  If you desire more "holding power", get a more agressive friction material rather than trying to cram more friction plates into the drum.

 

There are some generalized design principles which can apply to almost all automatic transmissions, but also some which are specific to the particular transmission in question.

 

IF your mechanic seems to believe that his custom clutch stack is best, then get him to agree that if it doesn't work, he'll be doing any "undoing" work on his dime, not yours.

 

What prompted the need for the rebuild?  Just curious.

 

Happy Holidays,

NTX5467

[TexasJohn55]

On 12/14/2020 at 9:48 PM, TexasJohn55 said:

"You are not considering that there is a clearance spec on clutch pack. "

Oddly, there is NOT a clearance spec that I can find in the '55 shop manual. It only gives a clutch steel spec of .068"-.070" and .010-.014" dish or cone spec. No clutch fiber spec. At any rate, you can only fit 5 and 5 in a '55 assembly.

[Bloo]

15 hours ago, NTX5467 said:

Match what came out of your clutch packs, period.  If you desire more "holding power", get a more agressive friction material rather than trying to cram more friction plates into the drum.

 

I think there is some confusion in this thread between:

 

a) stuffing more friction plates in than what the car was built with (not a good idea and probably not possible), and

 

b) possibly shimming the clutch pack with an extra steel, (or a selective-thickness steel spacer, or a selective thickness snap ring, or something like that) to get the end clearance of the clutch pack right.

 

a) should not be done while b) is a normal part of a competent rebuild on almost any automatic transmission in almost any make of car. The awful truth is that "rebuild kits" almost never have everything you need to get the end clearance right. Sometimes an extra steel, or the original steels (if still good), or another parts order. Usually another parts order for some kind of a shim.

 

If there is no end clearance spec, I just don't know what to say. If the new parts do not conform absolutely to Buick's original design, It might not end well. 

 

 

[Mudbone]

On 12/14/2020 at 11:18 AM, avgwarhawk said:

This may help:

 

 

 

 

My trans was rebuilt not too long before it was parked. The clutches were like new so I used them over again. There were many mistakes made when this thing was rebuilt long ago. Torque converter thrust washer was missing and it had the wrong valve body gasket installed. I can't believe it worked! My trans has not been road tested yet so time will tell if I put mine together correctly.

[drhach]

It seems that if you have a thickness spec for the steels and the friction disks and you have a specified count, you can come up with the required overall thickness. There's you spec. Is there a +/- as well?