Hard shift from second to third gear
 

Guys,

I have a '70 c10, 402, th400, LWB. TH400 tranny shifts extremely smooth from 1st to 2nd and 3rd to 4th. However when it shifts from 2nd to 3rd, it slams into gear. At low rpm it isn't as noticeable but given a little throttle, as soon as it shifts into 3rd, there's a hard jolt! Again, upshifting in other gears is smooth as well as downshifting is good. Any ideas?

Re: Hard shift from second to third gear
 

th400 only has 3 speed

Re: Hard shift from second to third gear
 

Duh! You're right, somehow when I was typing details I thought I had too many shifts...ha!

The hard shift occurs when shifting from 1st to 2nd gear. 2nd to 3rd shift is very smooth.

Re: Hard shift from second to third gear
 

Make sure your vacuum modulator is connected or adjusted

Re: Hard shift from second to third gear
 

http://chevroletforum.com/forum/silv...nd-gear-52050/

I think this would apply to a 400 as well, not sure.


"Drop the pan back down, remove the 1-2 accumulator housing and pull the piston. Check for a torn piston seal or broken spring, but moreso for a wobbled out piston hole, which is probably the culprit."

Re: Hard shift from second to third gear
 

Thanks guys for your input. I'll give both suggestions a try and report back!