1971 Riviera GS transmission code question

[George Buick Riviera]

Hello,

I started to investigate the GranSport features in my 71, and while engine is coded TA, rear axle has a tag (however I would like to ID it in future as well), but transmission is a mystery for me. Accordingly to 71 Riv manual, it should be coded "OW" - I believe. But mine is not.

Any help, guys ?

[bob71GS]

You are looking at the wrong codes. Trans code BB & OW are for the Skylark model with the Stage 1 engine. You can find all the info on the Boattail Registry web site under library. Boattail Riviera's by BUICK - Library - Links All 71 Riv's should have a BT code transmission. Rob Hayes who is maintaining this site has documented all of this. In checking my 69 Buick Service manual, trans code BU is for a Lesabre with the 350 engine, that would make it a turbo 350 trans and not a 400.

Bob Bonto #277 ROA

Technical Advisor 71-73

[RivNut]

Here's a quick way to see if Bob is correct (and I'll bet he is.) Check the configuration of the pan. Each transmission has a unique shaped pan.

Pan #3 is from a TH350 - what Bob says your numbers indicate

Pan #4 is from a TH400 - what you would hope you have.

[George Buick Riviera]

Thanks for help my friends.

Bob: of course I have manual for 71. Maybe I just understand wrong the transmission ID table (attached below). In the Riviera model there is nothing about special transmission for GS version, so I was assuming the last position is covering also Riviera GS version.

Sure I will check the links at Boattail registry, but should I understand then, that in Riv 71 transmission is coded "BT" for both: GS and non-GS models ?

By the way - I will register at Rob's site, I should do it months ago when Rob send me registration forms ...

Ed: going right now to garage to shoot the pan.

[George Buick Riviera]

Here's a quick way to see if Bob is correct (and I'll bet he is.) Check the configuration of the pan.

Each transmission has a unique shaped pan.

Pan #3 is from a TH350 - what Bob says your numbers indicate

Pan #4 is from a TH400 - what you would hope you have.

Well, here is a picture of my pan (attached below).

Any ideas ?

Edited April 20, 2011 by buick-riviera.pl (see edit history)

[bob71GS]

All 71 Riv's including GS's should have a BT code trans. I also own a 71 GS that I ordered new. My 71 only has 19,000 miles on it today. It has the BT code trans.

Bob Bonto #277 ROA

Technical Advisor 71-73

[George Buick Riviera]

Bob, thank you for your post

All 71 Riv's including GS's should have a BT code trans.

Aha - this is how I should understand the table from manual :cool:

Do you know if there was any dfifference in GS-nonGS transmission calibration, like in 65 GS, to switch the gears in higher engine RPMs ?

I also own a 71 GS that I ordered new. My 71 only has 19,000 miles on it today. It has the BT code trans.

Sounds like a dream !

[RivNut]

The pan in your photo looks like #4 in the illustration. Should be a TH400.

Here's a list of Transmission code numbers that I copied from the TeamBuick.com site. There is a BU coded TH400 listed for the 1969 LeSabre that had the 350 engine.

1969 350 V8 LeSabre BU

400 V8 Sportwagon AW

400 V8 GS 400 BA, BB

430 Wildcat & Electra BC

430 Riviera BT

1970 455 GS BA

455 GS Stage 1 BB

455 Riviera BT

455 all others BC

1971 455 GS BS

455 GS Stage 1 BB, OW

455 Riviera BT

455 all others BC

1972 455 GS BS

455 GS Stage 1 BB

455 Centurion high performance BU

455 Riviera GS other models with performance rears BT

Here's a link to a website that shows where to find the VIN of your car on the transmission. The site is dedicated to GS Stage1 cars, but there's some general information in it as well. Scroll down until you find your year then it will show you where to find the VIN on your transmission.

http://www.stage1registry.com/stage1info.html

Ed

Edited April 20, 2011 by RivNut
Post link (see edit history)

[JZRIV]

Apparently some 1969 LeSabres got the TH400 instead of the TH350 and thats what someone installed in your car. So you do have a TH400. BT code trannys shouldn't be too hard to find.....although probably not the case in Poland.

If something wasn't going to number match its much better to have the tranny not matched than that TA code engine!

Note: In 71, the VIN was also stamped on the tranny case.

[George Buick Riviera]

The pan in your photo looks like #4 in the illustration. Should be a TH400.

Yep - this is what is surprising me now......

Apparently some 1969 LeSabres got the TH400 instead of the TH350 and thats what someone installed in your car. So you do have a TH400. BT code trannys shouldn't be too hard to find.....although probably not the case in Poland.

If something wasn't going to number match its much better to have the tranny not matched than that TA code engine!

Note: In 71, the VIN was also stamped on the tranny case.

I've checked another transmission that I have in my garage (I bought it some time ago, to have it "just in case". As you wrote in Poland you will not find TH400 so easily). It is 71-BC. Still not "BT", but at least correct year & TH400 accordingly to the table from 71 manual. Anybody knows the difference between "BC" & "BT" ? In the table I can not see any ....

What do you think people, should I stay on BU-69, replace it with 71-BC, or hunt for 71-BT ?

Edited April 20, 2011 by buick-riviera.pl (see edit history)

[RivNut]

If I were you, I'd drive the car the way it is until you have to do something with it. When it comes to that time, you could have the extra trans rebuilt then just R&R them and you'd be back on the road very quickly.

Unless you're concerned with shift points or shift firmness (the basic difference between different code TH400's) you'll be fine. These are controlled by the valve body and the number, style, and thickness of the plates in the transmission. You can have any transmission rebuilt to what ever specs you want. One other difference looks like it could be the number of teeth on the drive gear for the speedometer. A possible difference between the BC and BT transmission could be whether it was controlled by a column shifter or a floor shifter - just the difference in the configuration of the linkage. ?????

Are you going to put the car in shows where not having the correct transmission will cause you to loose points? Is there anyway you can find out from the previous owner how long the '69 transmission has been in the car or where the original one is?

Drive it and enjoy it. It took quite a bit of research to come up with what you have. How many people in Poland are going to go through this to see what you really have. I would think that the rarity of the car would be enough to impress anyone who might have an interest in it.

Ed

Edited April 20, 2011 by RivNut (see edit history)

[JZRIV]

Yep - this is what is surprising me now......

I've checked another transmission that I have in my garage (I bought it some time ago, to have it "just in case". As you wrote in Poland you will not find TH400 so easily). It is 71-BC. Still not "BT", but at least correct year & TH400 accordingly to the table from 71 manual. Anybody knows the difference between "BC" & "BT" ? In the table I can not see any ....

What do you think people, should I stay on BU-69, replace it with 71-BC, or hunt for 71-BT ?

Maybe the tailshaft is slightly different between the BC and BT? Other than that probably real close to the same. I'm no tranny expert though.

If you are happy with the way the car accelerates and shifts you could leave it alone. On the other hand since the LeSabre had a 350 and the Riv a 455 plus being a heavier car, I would think the shift points would be noticeably different on the BU and BC trannies. The only way to tell if the difference is enough to warrant a change would be to try it.....unfortunately.

I wouldn't change it just to make the numbers closer to what it should.

Edited April 20, 2011 by JZRIV (see edit history)

[George Buick Riviera]

Are you going to put the car in shows where not having the correct transmission will cause you to loose points?

Drive it and enjoy it. How many people in Poland are going to go through this to see what you really have. I would think that the rarity of the car would be enough to impress anyone who might have an interest in it.Ed

No, no shows of this level in Poland. But I would feel better

And you are right - everybody is impressed enough just with the Boattatil line - starting from me, each time I see her ....

Is there anyway you can find out from the previous owner how long the '69 transmission has been in the car or where the original one is?

Ed

I will try to find out. Maybe this will work out ...

It took quite a bit of research to come up with what you have.Ed

Yep - many posts, but I'm impressed with the help from all of you ! My first post in that matter was just about 20 hours ago .....

I think I will end up like this: since she will get frameoff restoration (not sure if this year, most probably next one), I will simply prepare 71-BC that anyway I already have as a spare, then I will just install it while resto works.

I think it also make sense from this point of view:

Since the LeSabre had a 350 and the Riv a 455 plus being a heavier car, I would think the shift points would be noticeably different on the BU and BC trannies.

plus bigger torque of 455......

Thanks again folks. This was big help !

Happy Easter to all

P.S. I've checked the tags on my 65 GS transmission - at least that one is BS-65 :cool:. Situation here was similar: I was checking previously engine code+numbers, but not tranny....

Edited April 20, 2011 by buick-riviera.pl
P.S. (see edit history)

[bob71GS]

Ed,

I don't know of any car show except maybe Bloomington Gold for the Corvette's where a judge would attempt to crawl underneath a car and start checking tranny code numbers. That is about anal retentive as it comes.

Bob Bonto #277 ROA

Technical Advisor 71-73

[Guest Grandsport]

George,

What we know for sure is your Riviera left the factory with a BT transmission because it's a GS Stage1 car.

Also, I have found 1971 Riviera's with BC transmissions with the correct vin number, proving they are original. However, all BC trans. came in standard rivs. not GS Stage1.

Standard rivs. have a 2.93 rear end gear and GS had a 3.42 rear end gear.

1972 and 1973 manuals state, all riviera BC trans. and riviera GS Stage1 BT.

1971 manual is the only one that read BT for riviera and BC for other full size Buicks.

It appears that the 1971 manual was incorrect.

Now if you run a BC trans. in front of a 3.42 gear, your speedometer will not read correctly and you will show more miles than you are actually driving.

That can be fixed by replacing the speed gears.

As for any other differences, I don't know of any.....but I suspect there are some.

Grandsport.

[George Buick Riviera]

Just short info for all the previous posters: we've exchange many mails together with Mr. Grandsport last days. He was so kind to get in contact with few of his friends, and they've checked trannys ID & VINs (including Riv 71 GS - like mine). So above conclusion is based on that investigation.

Moreover - and what is interesting - one of his friend owns Riv 72 GS, and just guess what transmission is inside, yes, 69-BU.

Is it accidentally or in purpose ? Why the trany guys are putting 69-BU to replace 71 and 72 BT GS tranys ?

Please read last two posts at the bottom of the page

Edited April 23, 2011 by buick-riviera.pl
Link added (see edit history)