Hard shift from second to third gear - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OUbesto · 10-19-2016, 05:18 PM

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?

firedemon · 10-19-2016, 08:27 PM

th400 only has 3 speed

OUbesto · 10-19-2016, 09:09 PM

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.

trac209 · 10-19-2016, 09:35 PM

Quote:

Originally Posted by OUbesto

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.

Make sure your vacuum modulator is connected or adjusted

**WorkinLonghorn** · 10-20-2016, 01:58 AM

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."

OUbesto · 10-20-2016, 11:19 AM

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

10-19-2016, 05:18 PM	#1
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	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? __________________ 1970 C-10 CST, LWB, 402/400, A/C

10-19-2016, 08:27 PM	#2
firedemon Registered User Join Date: Jun 2015 Location: @ Posts: 890	Re: Hard shift from second to third gear th400 only has 3 speed

10-19-2016, 09:09 PM	#3
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	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. __________________ 1970 C-10 CST, LWB, 402/400, A/C

10-20-2016, 01:58 AM	#5
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	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." __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

10-20-2016, 11:19 AM	#6
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	Re: Hard shift from second to third gear Thanks guys for your input. I'll give both suggestions a try and report back! __________________ 1970 C-10 CST, LWB, 402/400, A/C



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