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Username Post: 261 six to TH350        (Topic#358669)
McCargar 
Poster
Posts: 51
McCargar
Reg: 12-07-11
11-01-19 08:34 AM - Post#2779295    

Has anyone adapted a 1961 Chevy 261 six to a TH350 transmission? I understand an adapter plate is needed but I am unable to find one.
Wayne



 


56sedandelivery 
Dedicated Member
Posts: 5692
56sedandelivery
Age: 68
Loc: Everett, Wa.
Reg: 02-26-08
11-01-19 09:51 AM - Post#2779307    
    In response to McCargar

Bentzen's, AKA TransmissionAdapters.Com. $$$, they are't cheap! I am Butch/56sedandelivery.




 
rrausch 
"15th Year" Silver Supporting Member
Posts: 14129
rrausch
Loc: L.A, Cal. & St. Louis...
Reg: 04-07-03
11-02-19 03:04 PM - Post#2779394    
    In response to 56sedandelivery

Are there other transmissions that might work as well without an adaptor?

1953 210 Convertible, 261 with dual Carter YF 966S carbs, P.S., Remote Bendix P.B. Booster... shade-tree restoration about done.




 
KaelFarmer 
Senior Member
Posts: 1041
KaelFarmer
Loc: Eau Claire, WI
Reg: 03-28-02
11-03-19 03:11 PM - Post#2779479    
    In response to rrausch

It is my understanding that for an automatic transmission, only the early model powerglide will bolt up without an adapter.

Here is a link to an adapter and starter available through Langdon's Stovebolt Engine Company. I am not sure if the pricing is current as other areas of the website show updates as of 2017.

http://www.langdonsstovebolt.com/store/#!/Transmis...


I bought an adapter kit a few years ago off of the classified section on the HAMB.

To the original poster, are you set on using an automatic? I know many people using a manual transmission have converted to either a Saginaw 4 speed (adapter used to be available through Patrick's Antique Truck parts to keep closed driveline) or a T-5 for overdrive.

Kael





 
KaelFarmer 
Senior Member
Posts: 1041
KaelFarmer
Loc: Eau Claire, WI
Reg: 03-28-02
11-03-19 03:21 PM - Post#2779480    
    In response to KaelFarmer

I also know that forum member 53Chevy is using a 700r4 transmission behind his 261. He used the adapter that I linked above. The main difference between the TH350 and either the 700r4 or the 2004r transmissions is that either of the other 2 provide an overdrive gear.

If you have not already considered this, all of the listed transmissions (except possibly the 4 speed Saginaw) will require a conversion to an open drive line as well.

Kael



 
drew1987 
"6th Year" Silver Supporting Member
Posts: 3360
drew1987
Age: 32
Loc: Rochester, New York
Reg: 02-23-14
11-03-19 05:42 PM - Post#2779484    
    In response to KaelFarmer

I remember something a while ago saying the 235 and th350 didn’t play nice. Obviously the 261 has more power but has anyone done this and can they confirm it, with a decent rear end, is pleasant?

Andrew D. Carapella (Drew)

'50 Deluxe 4dr v8 auto

Member:

Rochester Street Rods - Est. 1970
http://www.rochesterstreetrods.org

CrossMembers Car Club - Hebrews 12:2
http://www.crossmemberscc.com


 
McCargar 
Poster
Posts: 51
McCargar
Reg: 12-07-11
11-04-19 08:15 AM - Post#2779523    
    In response to drew1987

Thanks for all the input it's much appreciated and much to think about.

Wayne



 
100fires 
Poster
Posts: 97
100fires
Loc: Santa Fe Springs, Ca
Reg: 04-15-15
11-05-19 12:43 PM - Post#2779611    
    In response to McCargar

Buffalo Enterprises make one. He actually recommend a TH350 trans.



 
KaelFarmer 
Senior Member
Posts: 1041
KaelFarmer
Loc: Eau Claire, WI
Reg: 03-28-02
11-05-19 04:14 PM - Post#2779628    
    In response to 100fires

  • 100fires Said:
Buffalo Enterprises make one. He actually recommend a TH350 trans.



The last time I checked, Buffalo Enterprises was highly recommended but did not have a webpage or much internet presence. Apparently, Buffalo Enterprises is a 1-man shop so a phone call works best.

Here is the contact information that I had from a few years ago.

BUFFALO ENTERPRISES
25625 Dahl Road, Arlington, WA, 98223
(360) 652-7684



 
KaelFarmer 
Senior Member
Posts: 1041
KaelFarmer
Loc: Eau Claire, WI
Reg: 03-28-02
11-05-19 04:48 PM - Post#2779630    
    In response to drew1987

  • drew1987 Said:
I remember something a while ago saying the 235 and th350 didn’t play nice. Obviously the 261 has more power but has anyone done this and can they confirm it, with a decent rear end, is pleasant?




While I can't speak directly to friendliness of the 235/ TH350 combo, I can provide a couple of comparisons. I hope this doesn't muddy the waters regarding this dicussion.

If I remember correctly, the gear ratios for a TH350 are very similar to the 3 speed manual units. When the TH350 was used in production cars, the other commonly available GM automatic was the TH400. The TH350 functioned very well behind many low powered engines of the late 70's


My first car was a 1955 Chevy with the 235/ powerglide combo. The only modification I was aware of was that the engine had been bored .40" over. I also had the pleasure of driving another 55 with the 235 and 3 speed manual transmission. Overall, I can tell you that I liked the driving experience of the manual transmission better. Although, because of the rear gear ratio differences, the powerglide was slightly more pleasant at highway speeds.

I also got to ride along in a 56 that had a 4 speed (saginaw, I think) mated to the 235. All I know about this car is that the transmission came from a Vega. I also liked this drivetrain more than the 235/ 3 speed combo because the car didn't seem to have to work as much between gears, I originally didn't think much about doing the conversion myself because most Vegas I was aware of had rusted away and weren't kept around for very long in the local wrecking yards.

I also owned a 79 Nova with the 250 straight 6 and TH350 combo. A friend of mine owned another 79 Nova with the straight 6 and 3 speed manual. While I don't believe there any significant power difference between my 250 and my 235, I can tell you that the TH350 was a much better driving experience than the powerglide. I would definitely not say that this engine/ transmission combo was unfriendly toward eachother. Although, truth be told, other than the shift linkage occasionally binding, I preferred the manual Nova over the automatic one.

I also have had the pleasure of a ride along in 53Chevy's car with the 700r4 trans. Other than having an overdrive gear with this transmission, I don't think I noticed a significant difference in the riding characteristics between his car and my former Nova.

If I was planning to do a transmission conversion while keeping the 235 (or changing to a 261), I would always prefer a manual transmission.



Kael





Edited by KaelFarmer on 11-05-19 05:08 PM. Reason for edit: No reason given.

 
Idaho 
"10th Year" Gold Supporting Member
Posts: 482
Idaho
Loc: Upstate New York
Reg: 03-02-07
11-05-19 07:25 PM - Post#2779639    
    In response to KaelFarmer



Attachment: gear_ratios.jpg (1.7 MB) 5 View(s)




1953 210 Chevy convertible, 1953 210 Chevy Handyman station wagon, 1957 GMC Suburban Carryall.


 
KaelFarmer 
Senior Member
Posts: 1041
KaelFarmer
Loc: Eau Claire, WI
Reg: 03-28-02
11-05-19 11:10 PM - Post#2779645    
    In response to Idaho

Idaho,

Thanks for including that chart. While I fully understand that Mr. Langdon had far more knowledge and experience than I do, I have found that grading chart to be confusing each time that I have looked at it over the years.

As I previously indicated, the TH350 and 3 speed manual transmissions have very similar gear ratios. It is also my understanding that an automatic transmission requires more engine power than a manual transmission does. With that said, I haven't been able to get a clear understanding of the grading process that was used for this graph.

When comparing the TH350 to the 3 speed manual with a 2.54 first gear, I would expect that the grades would be similar and most likely would always favor the manual transmission because of the parasitic power loss of the automatic. However, according to the chart, with a 4.11 rear ratio the manual scores a C+ vs the automatic's C-. Even more surprising is that with a 3.55 rear gear, the manual actually scores lower than the 4.11 gear by obtaining a C- in comparison to the automatic's score of a B-. That is a full letter grade of difference. According to the way I was graded in school, that approximately a 15% difference in scoring criteria. The only thing that I would think my create that difference is the need to slip the clutch in 1st gear, but there are plenty of people who have changed their 49-54 Chevy to 3.55 gears without needing to excessively slip the clutch to get moving.

To answer Drew's comment earlier, even though I find the chart confusing, a drivetrain choice that scored a B- sure seems to be much friendlier when compared to the factory original D-.


Kael




 
100fires 
Poster
Posts: 97
100fires
Loc: Santa Fe Springs, Ca
Reg: 04-15-15
11-12-19 04:08 PM - Post#2780065    
    In response to KaelFarmer

If he does not answer leave him a message, he will call you back. I found him very knowledgeable and he machines all his own stuff. He does not have a website, I think because he is older and it a one man business.

When I bought my adapter from him he was willing to sit on the phone answering all the questions I had and he sent out written instructions on what I had to do to install the adapter. I highly recommend his part.

As for it fitting a 235, I put it on a 261 but the blocks are the same from everything I have read. The differences are with. The internals.

Hope it helps



 


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