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40 Century won't shift when warm


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A 40 Century came in to the shop today. New owner. Complaining that he can't use 1st/R after the car has been driven and is warmed up. 2nd and high work fine all the time. It appears that someone recently had the tranny out. So we drive it and it works fine. Go around the block a couple of times and then no low/reverse.  Doesn't matter if the engine is running or not. If you wait for 20-30 minutes it releases and works fine. Am reluctant to pull the tranny as it will be cold and it will be working fine so I was hoping for some ideas on where to go with this first. 

We may open the floor up and remove the inspection cover (6 bolt tranny) to look in there when this is happening. 

Any ideas would be appreciated.

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Having recently removed and rebuilt the transmission in my '41 Super (with a lot of help from my friends!), I'm trying to figure out what could possibly be going on with this Century.  The most difficult aspect as far as diagnosis for me is the fact that it works fine when cold but no longer works when it's warmed up.  None of the suggestions so far account for the fact that works fine when cold.  I guess my first question would be: was it working okay before the transmission was removed by the previous owner?  What was the reason for the previous transmission job?  What was done?  If you could find out who did the previous job and have the opportunity to talk to them, you might be able to get some answers to these important questions.  Also, maybe a dumb question, but have you checked the fluid level in the transmission?  Is it possible that something is overheating because the transmission oil level is down?

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All good points fellas and I thank you for the quick response. Fluid level is where it should be according to my friend who has looked at it yesterday. I am going up to the shop this morning to crawl under the Century and have a look at other things. As far as I know right now the owner has no history with the car having bought it just recently nor do I know if he has any ability to speak with the previous owner. There was a hint from my friend that this was an estate sale implying that the p/o may be deceased.

I have had quite a few selector trannies apart before but can't quite understand this heat/friction issue locking out 1/R. Who knows at this point what someone has done with this tranny. Guess we get to play "Sherlock" here. Got to get a look inside first.

Does anyone know if there is an inspection cover in the floor that can be removed to get access to the top of the tranny? We have to look at this when it is stuck and warm. If we take it out of the car it will be cool and working. Guess we could cut the floor but I hate to do that as this Buick is in great shape.

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 Thanks Dave for the heads up. The owner took the car back last night so I did not accomplish much this morning. We are scheduling him back soon and then we will take a look.  I will update this at that time. Also, I had thought this was a sedan but Bruce tells me that it is a convertible.

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On 8/20/2020 at 7:08 PM, Wogden said:

Does anyone know if there is an inspection cover in the floor that can be removed to get access to the top of the tranny? We have to look at this when it is stuck and warm. If we take it out of the car it will be cool and working. Guess we could cut the floor but I hate to do that as this Buick is in great shape.

Yes.  Easier if you take the front seat out

Image below is of a 1939 series 40 Special RHD.  1940 Century uses the same basic body shell. Century transmission has a 6 bolt cover

1939 41 gearbox 03.jpg

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Has anyone heard about someone making their own inspection cover for the 1941 cars? I was also surprised when I went searching for it in my ‘41 Roadmaster and could not find it.   Very disappointed . I suspect they may have been thinking about retaining the integrity of the glued down sound deadening material.

 

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Sounds like a bad rubber bushing or mal adjusted selector lever. When cold holds shaft holds lever in the low-reverse position.   When hot the resistance was gone.    The "neutral" position is between 2nd and 3rd normally, trans lever has to be lifted for neutral between low and reverse.   another possibility is the shifting forks and neutral lever were assembled wrong.  One check ball or spring overlooked will cause things not to work right.       Bob (jr) at Bobs Automobilia has parts and knowledge on these large series transmission    805-434-2963

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Good point on the adjustment Critter. I am hoping that it will be that simple of a fix. Wondering if any member has a shop manual for the 40 Century that show the detail of the shift linkages. This unit has been out of the car before and it may not have been reinstalled correctly with respect to the linkages/tension spring setup. Can someone attach a picture of this and the adjustment procedures?

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18 hours ago, Wogden said:

Good point on the adjustment Critter. I am hoping that it will be that simple of a fix. Wondering if any member has a shop manual for the 40 Century that show the detail of the shift linkages. This unit has been out of the car before and it may not have been reinstalled correctly with respect to the linkages/tension spring setup. Can someone attach a picture of this and the adjustment procedures?

Download the 1942 Buick shop manual. All of it section by section. The pdf link does not work.

http://www.oldcarmanualproject.com/manuals/Buick/1942/Shop Manual/

It is very comprehensive and has information that can be used with all straight 8’s.

It has more information than was included in older “Shop Manuals” before 1942-41

You want section 7 pages 201 to 216

 

Page 118-A below is from 1928-52 parts manual does not indicate which series. Has another page for 1941 to 52

1928-52 Master Parts Book pg 118-A.jpg

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  • 1 month later...

UPDATE

finally got the Buick back in the shop. As it turned out the insulator for the lower control rod to the selector finger was worn out allowing just enough slop

that it would interfere with 1st/R selection. The insulator sets on top of the steering mast right next to the engine. When heated by the engine it became softer providing just enough extra slop to interfere with proper gear selection. Replaced the rubber insulator with a 50 cent bushing and away she drove!

Thanks for all the input fellas. Pretty basic simple fix. The owner was tickled to say the least.

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