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-   -   Diaphragm v/s Coil spring Clutch for the KMT90 (https://www.team-bhp.com/forum/4x4-technical/117189-diaphragm-v-s-coil-spring-clutch-kmt90.html)

Hi,

My jeep has a peugeot XDP with a KMT90 tranny. I got my clutch replaced from the coil spring type to a diaphragm type. I find the diaphragm to be very hard (trust me its hard). My mechanic suggests to revert back to coil spring. Even though I find the clutch to be hard I like the launch response. What do you guys suggest.

Thanks
Satish

I would prefer to keep thy diaphragm clutch, see if you can improve the feel by changing the length of the levers or installing a hydraulic actuation system

Satish,

I know what you mean by hard.

I too have the same problem with my diaphragm type. My CJ340 (with a army KMT-90, suspended pedals) is a very comfortable ride with power steering and all, though I am used to the hard clutch, but anyone who drives it really complain.

Question to Arka, Sir Behram and other Guru's is...How do I make the present set up softer or what if I use the spring type pressure plate over the present, any advantages or disadvantages ?

There is an option of hydraulic clutch but I would want to try out other options before the conversion.
Regards,

Hi Satish,

1) The Diaphragm Cover assy has better actuation, hence softer than the Coil-Spring assy.

2) Check the Clutch Linkages for
a) Proper Alignment
b) the Clutch Pedal Pivot Rod on the Chassis, has two bolt holes, use the lower Bolt Hole, for softer feel.
c) Check the Mush Room type Pivots on the Chassis and Gear Box (Clutch Actuation Fork pivot) for wear.

3) Grease the Clutch and Brake pedal bushing/Pivot Rod.

Regards,

Arka

This is strange. My experience says that the coil spring clutch is significantly harder. (In fact, I squarely blame the Jeep coil spring clutch for my knee and hip troubles!)

Instrumented tests required!

Regards
Sutripta

me too.. I use my jeep on daily basis (60km avg). Pumping the clutch frequently has made my left leg's muscle stiffer and stronger at the same time I have started to suffer from knee pain.

Back in the old days (ahem) among high-performance enthusiasts in the U.S., diaphragm clutches were not favored due to their tendency to be negatively affected by centrifugal force at high rpm's. Something about the configuration could cause the diaphragm blades to partially release / allow the clutch to slip under such conditions. I had a V-8, circa-350bhp vehicle that benefited greatly from the change to a slightly larger diameter coil-spring-type pressure plate; compared with the original diaphragm-type, it also required a lot more pedal effort. Of course, a diesel-powered Jeep is never going to see very high revs (or bhp), so it'll come down more to what sort of feel the driver prefers. Very likely, different aftermarket manufacturers / remanufacturers here in India use coil springs of widely varying ratings, hence the inconsistencies in the experiences of other posters. I seem to remember that there was something design-wise that generally made diaphragm-types a little easier on the left leg - but in general, it probably depends more on the actual spring materials in use, and THAT will probably depend on the specific supplier / day of the week... :)

As Arka indicates, a hard pedal can be somewhat compensated for via "mechanical advantage" (i.e., different holes in the linkage providing, essentially, more leverage) - though the pedal travel would also become excessively long if one tried to push this advantage too far.

By its configuration, a diaphragm exhibits a falling rate characteristic. And short of changing it, there is very little one (the end user/ shade tree mechanic) can do to change the characteristic and values. On the other hand, coils spring clutches would be easier to tweak.

Regards
Sutripta

My jeep was taken for an overhaul few days back. I reverted back to coil spring type. I still found the clutch to be hard. Then as Arka suggested, I used the lower bolt hole in the clutch pivot rod. It was very soft. But this lasted only for a few days and now my clutch is hard yet again. :Frustrati

I think the only way to make the clutch "Light" is to use Hydraulic actuator. The clutch is hard as the springs have to push the clutch plate with quite some force, else it will slip under high torque.

In case the you have a light clutch with shorter throw, it will slip under high torque - first gear lower ratio is the most demanding scenario.

ARoy, My Cj's clutch is smoother than most cars, like arka said the entire actual linkage system needs a good checkup and dieselwash + grease up!

Satish - Answer these...

1) Is your pedal a suspended or a into-the-floor type?
2) What bell housing do you have? Meaning is the starter motor on the driver side or co-driver side?
3) Wrt to 2 - where is the clutch cable linked to? Driver side or co-driver side?
4) Wrt to 2 and 3, what clutch cable are you running, the 6 foot loooong one? Or the tiny 7 inch one?

In the last 2 years I have had a fair brush with many types of clutch linkage systems and (for the manual one) found the old to be gold (7 inch linkage with the greaseable fork)!!

PS - Last week I came across this jeep (a) starter motor on codriver side (b) suspended pedal for manual clutch (c) the cable from top of the firewall, dropping below the left leg of the driver, doing a u-turn behind the GBTcase, going towards the bellhousing and actuating the clutch - It was a OE Setup (IIRC from the 1st gen Armada) and it was a sad way to actuate the clutch - Knee was dead!!

We altered the same setup with (a) a square hole cut on the bell housing on the driver side for the reversal of clutch release bearing Y fork (b) new clutch fork greaseable type below drivers feet on chassis (c) same suspended pedal but a shorter clutch cable (about 3 feet) from early MM Pickups and some misc things... the feel is a LOT better now!

Sharing a similar pic of the Part ,of which angle ( wrong one ) caused heavy clutch in my 89 model 540 . To my surprise it was an OE part that came with the vehicle :Frustrati

After the change with a ' Proper Part ' the clutch was unbelievably smooth



Sudarshan

Pic is from net some where , all thanks to the original poster .

Thanks all for the reply.

@Aroy : My clutch seems to be relatively hard when compared to other manual clutches.

@svsantosh :

1. Mine is a floor type pedal
2. Starter Motor is on the co-driver side
3. Clutch cable is linked towards the driver side.
4. I am not sure on the clutch cable length (6 foor or 7 inch). I will get under my jeep and give you that asap (also some snaps if possible). I hope you are referring to the one highlighted in red rectangle in the below pic.

I too suspect the clutch linkage now, the pedal shaft, highlighted in yellow rectangle seems to be worn out. When I de-press the clutch, the break pedal goes in and the brake pedal has a wobble.



You have mentioned on the 7 inch linkage with greaseable fork. Can you explain more on this. Any supporting pictures greatly appreciated.

Sathish - reattach the pic, cant see it? ^^

Bhai, Satish - see my experiments with the OE pivot rod, it still works and is butter smooth... at least better than before! For some reason this didnt have the 2nd hole, we just made it!

http://www.team-bhp.com/forum/4x4-ve...ml#post2416913

this is the 5~ inch clutch cable that comes in this old 540's cj's. Thats the only cable :) so very less chance of excess play and knee pain, but the pivot rod needs to be perfect!

just applied simple physics of lever/fulcrum.

Re-attaching the PIC...

Santosh, the pivot rod I have already has two holes but are adjacent and not aligned horizontally (like your modification). I think its better I post some pics soon for a better understanding. Meanwhile, can you please provide some info on the greaseable fork.. :)