Reverse kicks

[jimmyjimwas]

Hello,
My problem is that when i put my 1985 m1008 into reverse it kicks in kinda hard,
i was also reading about maybe the idle isnt kicking down would that cause
this issue? I have checked the tranny fluid and its good..any ideas
thanks

 

[Bob H]

A high idle speed can cause that.
bad u joints can cause that
worn out differential can cause that

I'll guess that after you've backed up it will feel like it hit hard back into drive.

 

[jimmyjimwas]

Yes when I put it in drive its a little rough,also while sitting in traffic seems to idle fast now i think about it.. I will check the high idle it does seem it won't kick down like I have heard from other trucks m1008.. I suppose you need to unplug it to test it, from what i read on this site. The truck only has 23000 miles had it a year but havent really started driving it till now so ill go from there first..
Any other help would be welcomed

 

[TGP (IL)]

Check what was mentioned to be safe, but the TH 400 in the these trucks and the civilian K series were known to shift hard between forward and reverse.
It has to do with the way the accumulator in the valve body is set up.
GM did address that issue later on,after 87 or so.
Tom

 

[rtk]

How are the rest of the shift's ? I would check all of the above . plus make sure your have vacuum to the modulator on the side of the trans . Bad vacuum hoses are common on these vehicles .

 

[jimmyjimwas]

Hi thanks
I did replace the modulator on the side of tranny when i got it, the rubber connector was cracking so I just bought new.
Does that modulator control the shifting while driving only? Thought thats what i read on posts here,,It shifts great driving ..
I did check the idle kick down and it seems to be working.it kicks down a little not too much is that normal?
I was wondering what does the screw on the idle kick down do?
Thanks for yor time