C-6 with chatter in reverse

A buddy of mine has a mid 80s diesel c-6 he built this c-6 and it chatters in reverse .Low and direct are fine .He built this after burning up this unit after over loading .It chatters worse in reverse on an incline .Also he told me before this build it did the same thing .Any thoughts let me know .To me it needs to come out but you need to be aware of what to look for .This is a diesel truck mid eighties .Thanks all ! Doug

Did he replace all the clutches?

According to Frank it is the boost pressure valve .He says it must be sticking .Yes he replaced all the clutches and plates .Just guessing but it probably takes a lot of pressure for reverse .The owner says it is good in low and everything else works good .Just a shudder in reverse which is probably slippage .I know a good shop near him maybe they will check it there.

manofmerc wrote:A buddy of mine has a mid 80s diesel c-6 he built this c-6 and it chatters in reverse .Low and direct are fine .He built this after burning up this unit after over loading .It chatters worse in reverse on an incline .Also he told me before this build it did the same thing .Any thoughts let me know .To me it needs to come out but you need to be aware of what to look for .This is a diesel truck mid eighties .Thanks all ! Doug

I had one built by a shop around 40 years ago that did the exact same thing. The only part they did not replace was the servo piston, as they built it on a Saturday and did not have one, and the parts shops were closed.

The Heddman headers on that truck ran right up against the servo, (it was cooked when we pulled it), and we suspect that did not help things either.

As I recall, it did not take long for the forward gears to go away.

I got your pm Greg It looks like it is in the valve body could even be the gasket .Probably Frank is correct your info mentions the boost pressure valve also Thanks all for these ideas at least there is a little action on here .Doug

This fellow is taking it to a reputable trans.shop so probably be a while .In you instructions they reference the boost valve and the gasket I wish he had an extra valve body but he doesnt .And I imagine a diesel valve body is hard to come by we will see thanks all Doug

The shop wants $2000 to check out his transmisson .That is with him pulling it .I really think all he needs is a check out on the valve body.I certainly would like to get that much to check out a c-6 .We will see. Doug

manofmerc wrote:The shop wants $2000 to check out his transmisson .That is with him pulling it .I really think all he needs is a check out on the valve body.I certainly would like to get that much to check out a c-6 .We will see. Doug

They want $2,000 just to check it out Wow,what would they want for a rebuild $5,000 or more!!

You know any shop would be scared of this one .But $2000 ? They just dont want to mess with it This same shop built c-6s for me .Back in the eighties it was around $300-$400 to pull and build .Really though I will try getting my buddy to find another diesel valve body to install .That is the best scenario .Finding one is the next issue .Fifteen twenty years ago if a friend needed a freshen up on their c-6 I would charge $100-$150 . Doug

They claim this kit will convert a C6 Gas Valve Body to Diesel.


https://www.ebay.com/itm/254609720072?fits=Make%3AFord&itmmeta=01HVE8306AT41A1NVWP2H62299&hash=item3b47ec0308:g:DPkAAOSwnbNluPHC&itmprp=enc%3AAQAJAAAA8Lup42W3alDyZ10jhpXKVz4TddczY5EJ6GLk9zDGPqDtndyWkZZqW3X93KwozqC2hYLH6QzrTPR58IQE%2Bp3n1KDV6Kpq23ti6i323hhcheBjna2V7CtfMlp5zHWg%2FhwiwAyL11J%2BG4V7gRV4C9g3cMVQOCyCtXvl%2FUOsVQnak9RYu6ZdzvC7DNcWk0k7%2BVRQWekWKb5DhXAI635Q4ZPshKlFXlJ%2BcSiy0%2BkLNDBzv6ED5NwyyrpNtDrUulWmtC4KENydrU2nGKZ7xGJ%2FyTvNsl8SG5Gm%2BL4fMSxHB02lWh7niLmzIhPKbfQ%2BXf5Mzxu5jQ%3D%3D%7Ctkp%3ABk9SR8iDjMjbYw

It says to use "a .410" or .437" Boost Valve that many gas valve bodies come with."

I don't believe it comes with the seperator plate gasket though?

Gregaust wrote:You know , that's not a bad option. I have used that kit in gas types works good .
There is some tips also for setup for the vacuum, just a thought to check there also

https://res.cloudinary.com/transgo/wbiss/sk/SKC6.pdf

^ That's a great link. They used to call it a Gil Unger shift kit back in the 1980's in the blue and white box.

The instructions back then mentioned Diesels but I don't recall them being that indepth.

They did not come with a notched vacuum modulator pin either.

I also don't recall them wanting the .055" to .063" hole drilled into the valve body by the booster partition.

I second the idea of testing the vacuum.

Make sure it has the Green Stripe modulator also.

The Superior Kit says "and Diesel" and the Transgo says "Converts Gas to Diesel Valve Bodies".

Looks like 7 springs in the Superior kit and 16 in the Transgo kit.

I would think both kits increase line pressure and should help reduce chatter.

^ Then again that Superior kit looks like it has a new servo piston spring, and does include a servo piston gasket.

I leaning towards the Transgo kit, as it is Clearly Advertised as a Gas to Diesel Conversion Option, as well as you mentioned, I have also used them in the past and they did good.

You all are working so hard .This is still a good forum for transmisson ?? My buddy is almost 80 years old I dont really know if he is up to pulling this valve body I will call him later this week just to check on him . Thanks for all the effort .Doug

Well it was the boost pressure regulator valve .According to my buddy.Jim he made a tool and with some scotch brite on a bit he made and hones the id of that boost valve cleaned the vb put it back together and the shutter is gone I guess it was sticking just letting you all know what it was .So tell me when is this valve in use .Is it in reverse only ? Does the big aluminum valve move or just the inner valve .Just for my own information. Thanks to you all Frank as well he knew what it was as well as others .Doug

This old boy is tough he is 78 and pulled that heavy son of a gun then built it and fixed the valve body !Former marine helicopter mechanic and retired airline mechanic !I am 65 and will pull my c-6 but I dont know about 78 we will see though .Thanks to you all Doug