The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-26-2014, 04:00 PM   #1
jasonconaway
Registered User
 
Join Date: Mar 2014
Location: Fuquay Varina, NC
Posts: 1
Converter lock up too soon?

I recently repalces some rotten vacume lines, and caped some that I wasnt sure where they went on my 84 c10 305 auto trans. . I know the one for the converter lockup is connected, but since I changed all the lines, when it shifts from second to third it is normal for about one second then its like it hits another gear and bogs the engine down a bit till I build up more speed. This is while accelerating easy. Seems fine when I get on it. There wasnt a big change in engine rpm when changing to 3rd before I replaced all the lines. What could be causing this bog? Is it locking up to early?
Thanks!
jasonconaway is offline   Reply With Quote
Old 05-26-2014, 09:18 PM   #2
Gmc-76
Registered User
 
Gmc-76's Avatar
 
Join Date: May 2013
Location: easton maryland
Posts: 93
Re: Converter lock up too soon?

I just started randomly having what sounds to be the same exact problem today, any feedback would be appreciated from me to!!
__________________
Andrew
85 Sierra Classic c10, 305/350/2:73(86k original)
instagram: anabb_98
Gmc-76 is offline   Reply With Quote
Old 05-26-2014, 09:58 PM   #3
50seven
Registered User
 
50seven's Avatar
 
Join Date: Sep 2011
Location: Out There
Posts: 88
Re: Converter lock up too soon?

As I remember the 700's don't lock up in first. They lockup in 2,3 & 4 unless they are told not too by the TV cable, manifold pressure switch or the break pedal switch.

I bypassed the vacuum switch because I was running a cam and the pressure switch wasn't right. Never had any issues other than not liking the 700r4's.

Check the TV cable is adjusted properly? Check The vacuum lines are not causing a massive leak somewhere? Put a temporary tach in for diagnosis should drop 200 rpm upon lockup and vice versa? Check the switch on the brake pedal it has adjustment in it also. But most of these faults would cause a non lockup issue.

I would have look at the vacuum switch first (did you take the wiring of this switch out of the equation or just cap off the vacuum lines)? They electrical portion is probably still trying to control lockup.
50seven is offline   Reply With Quote
Old 05-26-2014, 10:19 PM   #4
vwzkc
Registered User
 
Join Date: Jun 2012
Location: austin, tx
Posts: 6
Re: Converter lock up too soon?

I have the exact same problem, somebody told me it might be the governor in the trans. Idk. Curious to see some more responses though.
vwzkc is offline   Reply With Quote
Old 05-27-2014, 09:24 AM   #5
cadillac_al
Registered User
 
Join Date: Oct 2013
Location: Maine
Posts: 2,376
Re: Converter lock up too soon?

Did they ever work right in '84? My Dad bought a new GMC C15 in '84 and that thing never knew what gear to be in; even when it was new. We just lived with it for 5 years until he bought an '89. It probably is TV cable related but we weren't hip to that back then.
__________________
76 Chevy K20
76 GMC K15
77 Chevy C10
77 Chevy K10
cadillac_al is offline   Reply With Quote
Old 05-28-2014, 07:05 AM   #6
vwzkc
Registered User
 
Join Date: Jun 2012
Location: austin, tx
Posts: 6
Re: Converter lock up too soon?

Did anyone find out anything else on this subject?
vwzkc is offline   Reply With Quote
Old 05-31-2014, 02:20 PM   #7
beamn7
Registered User
 
Join Date: Oct 2011
Location: Wildomar, CA
Posts: 466
Re: Converter lock up too soon?

Seems almost all of these used to lock in 2nd or 3rd depending on engine load / how heavy your right foot is at the time. Can be very annoying as well as wear on the converter clutch and thrust bearing / crank after years of it....
I wired up a relay and a 4th gear pressure switch to allow for lockup only in 4th. Easy to do or you can buy a kit for this also. Many aftermarket kits available via summit, etc...
beamn7 is offline   Reply With Quote
Old 06-05-2014, 06:27 PM   #8
vwzkc
Registered User
 
Join Date: Jun 2012
Location: austin, tx
Posts: 6
Re: Converter lock up too soon?

Did anyone solve this? Would be nice if someone did to post a follow up.
vwzkc is offline   Reply With Quote
Old 06-06-2014, 01:39 AM   #9
jhngardner367
Registered User
 
jhngardner367's Avatar
 
Join Date: Feb 2012
Location: Austin, Arkansas
Posts: 248
Re: Converter lock up too soon?

It may not have the 700r4 trans.
Does the shift indicator have a "D",with a circle around it,and another "D",then 2,then 1? If not it is probably(as in my '85) a 350c trans.
These trans.,have a vacuum-actuated switch,usually located (looking from front of truck) in the upper left cowl area. It closes the solenoid,in the trans,to lock up the converter clutch to provide a direct fluid coupling( 1 to 1 drive).
When the brake is used,during stopping/slowing,it disconnects the solenoid,to allow the vehicle to idle without stalling.
Mine locks in at about 35mph.
The "bog" you feel,is the converter locking in,and is normal.
__________________
Always expect the unexpected,....but don't expect the unexpected to be the unexpected you expect !
I'm busier than a one-legged cat,in a sandbox!
Veteran..and proud !
I can't fix what ain't broke....you want I should break it?
jhngardner367 is offline   Reply With Quote
Old 06-08-2014, 04:26 PM   #10
vwzkc
Registered User
 
Join Date: Jun 2012
Location: austin, tx
Posts: 6
Re: Converter lock up too soon?

im pretty sure we are talking about a 350c trans and there would be no overdrive only d21 on the selector. not a 700. ive tried unplugging the connector on the trans and adjusting the kickdown cable, and checking the vaccum modulator and still same problem. im convinced its the governor in the trans. thats my next step unfortunately. i will post anything i find out.
vwzkc is offline   Reply With Quote
Old 06-08-2014, 04:49 PM   #11
gchemist
BAD BOW-Silverado XST
 
gchemist's Avatar
 
Join Date: May 2000
Location: Senior Member from Austin, TX
Posts: 6,431
Re: Converter lock up too soon?

Swap the govenor for a Vette one. Shifts will definately change. Connect a hand vacuum to the modulator line. Check for vacuum loss.
__________________
Gerardo a.k.a. Mad Chemist
Silverado XST videos
gchemist is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:55 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com