Quarter Master Throw out Bearing

[davidk]

This winter I'll be installing an HDVA 5 speed conversion. The hydraulic clutch release throw out bearing that comes with the kit states to use only Dot-3 (No Dot 5) fluid. I checked the Quarter Master website. It also says no Dot-5.

Does anyone know why? Has anyone used this throw out bearing with Dot-5? I'm currently using Dot-5 in my clutch (and brakes) and hate to go back. Thanks for your help.

 

[Don Elliott]

I suggest you ask Herman.

 

[DougF]

It is only a guess, but maybe the rubbers in the conversion kit are not compatible with Dot 5. Last summer, I had a slave cylinder deteriorate within 4 months while using silicone. I rebuilt with another company's kit and have had no problems since.

 

[RonMacPherson]

Agreed. The seals(modified o-ring design) in my first hydraulic slave throw out bearing(McLeod back in the late 80's) were not compatible with silicone fluid.

Worked fine for about two weeks after I put the t/o bearing in(after I pulled the tranny twice sizing the bushing as at that time it was for a small block Chebbie), until one day I pushed on the pedal and it was instantly soft and mushy.

Red over at McLeod(fortunately for me, at that time I only worked about 15 miles from them, so stopping over for parts and consultation was easy) told me that the rubber they used for longevity and heat resistance was not compatible with silicone... Never got around to seeing if anyone had compatible seals..

 

[BobbyD]

McLeod and Quarter Master both say that the O rings aren't compatible. A quick Google returned many responses saying the same thing. The DOT 5 "attacks" the O ring rubber and you end up with a leaky T/O bearing.

 

[TR3driver]

Any idea which 'rubber' that is?

 

[richards]

I have to tell you all that I am on my 4th McLeod TO.
Only use Dot 3....(not Dot 3/4).


I do not think Herman provides the McLeod bearing any more because the Quality Control on their T.O. parts was not good.

McLeod was purchased by a much bigger auto supply company, and the engineer/designer for the TO bearing no longer works for them..

My three bearings that were bad and all leaked were sent back to McLeod for testing, they Never Never told me or Herman what caused the leaks.

Herman was very helpful in getting me back on the road....great guy.

My current McLeod has been in my car for two years and does not leak (that is up to today).

 

[BobbyD]

Randall.... no idea....I'm just reporting what I read and can't argue a case for it either way. I've never used DOT5 so it wasn't a problem for me.

Richards.....My McLeod T/O bearing never made it to the road. I got the tranny and engine back in the car, started it up while it was on jack stands and tried to shift the new 5 speed. It was about then that I saw the steady drips coming from the bottom of the bell housing. I may have been the last McLeod T/O bearing Herman ever shipped and I may have been the first Quarter Master T/O bearing he shipped. He had just installed one in his car before a trip to Lake Tahoe and he wanted to make sure he had no problems before sending me one. Mine was rock solid from Day 1 and I believe that is now the only T/O bearing he supplies. When Herman got my McLeod back he bench tested it and said it wouldn't hold any pressure at all.....just drip drip drip.

 

[TR3driver]

no idea....I'm just reporting what I read

No worries, Bob, was just curious. My chart shows that polyurethane, neoprene and silicone O-rings don't work well with silicone grease (which I presume would also apply to silicone brake fluid); so such things clearly exist. But poly and silicone are also "not recommended" for brake fluid, while neoprene is only "fair, usually OK with static seals" with brake fluid; so none of these seem like a good choice in this application.