Shifting

[mack88]

my 12speed does not want shift when it starts to get colder.I was wondering how hard it is to rebuild the pisotn under the cab.Do i have to lift the back of the cab or drop the tranny thanks.

[Timothy Maikshilo]

my 12speed does not want shift when it starts to get colder.I was wondering how hard it is to rebuild the pisotn under the cab.Do i have to lift the back of the cab or drop the tranny thanks.

Try changing the air filter element on the tranny and that should take care of your problem. Sounds like moisture in the air system,Tim

[mack88]

Try changing the air filter element on the tranny and that should take care of your problem. Sounds like moisture in the air system,Tim

I did change it last summer at that time it did look clean on the inside.So i was thinking it should still be okay.Iv'e run about 275 hours since then.But i guess for what it costs i should try anuther one.

[Rob]

my 12speed does not want shift when it starts to get colder.I was wondering how hard it is to rebuild the pisotn under the cab.Do i have to lift the back of the cab or drop the tranny thanks.

I would jump on the air filter as a start and also ensure all of your air lines and selector valve(s) are airtight. I have never actually rebuilt a 12 speed top cover, but have plenty of six speeds. Just remove the center floor panel to the cab after removing everything needed to gain access, then unbolt top cover complete, take to workbench and replace everything that appears to be worn. Rebuild parts are readily available and will cost less than $100.00 unless something major is defective. Rebuilt shift cylinders used to be available as a complete bolt on setup but I've never had to replace the complete unit; only rings and seals.

Rob

[mack88]

thanks for the ifo. Rob it will be great help.

[MACKS]

Hard shifting in cold weather is a common problem with the 12 speed trany,a lot of guys inculding myself warm the truck up with the splitter in nutral and the stick in third gear, this helps alot,also make sure you have the right lube in the trany,if it's to heavy your going to have a lot of problems when it gets cold. Hope this helps,Good Luck

[mack88]

Hard shifting in cold weather is a common problem with the 12 speed trany,a lot of guys inculding myself warm the truck up with the splitter in nutral and the stick in third gear, this helps alot,also make sure you have the right lube in the trany,if it's to heavy your going to have a lot of problems when it gets cold. Hope this helps,Good Luck

I was told to use 80-90 gear oil only.thanks

[fjh]

What model of truck is it in?Just poping out the floor pan May not work in your application!

If its an rd or rw it is not a nice thing to do!You need to loosen the cab mount on the tube crossover at th rear of the cab if it is an air ride cab you need to take the shocks loose at on end!

[mack88]

What model of truck is it in?Just poping out the floor pan May not work in your application!

If its an rd or rw it is not a nice thing to do!You need to loosen the cab mount on the tube crossover at th rear of the cab if it is an air ride cab you need to take the shocks loose at on end!

Yes it is a RD688S.