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#1 |
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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1961 C30 4sp Transmission: swap choices?
Hello again.
I drove my new truck today for the first time (1961 C30 1 ton, 261 straight 6, 4 sp manual trans) and found a change I want to make right away: the transmission. As mentioned it's a four speed, 1st gear a granny gear, not worth using in normal driving, 2-4 are very short gears with a top speed of 55mph. As of now, I'm planning to keep the inline 6, but am wondering if there is a common tranny swap that gets your truck a better range and a top speed closer to 80-85mph. I'm having trouble identifying the trans based on the charts I have found on this forum and a google search. The Saginaw sounds like it might be common, but my inspection plate on the drivers side has 6 bolts instead of 7 (photo attached). Thanks Michael |
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#2 |
Registered User
Join Date: Sep 2014
Location: Valparaiso, IN
Posts: 300
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Re: 1961 C30 4sp Transmission: swap choices?
Your existing trans might be a Saginaw SM 420. ( https://www.novak-adapt.com/knowledg.../manual/sm420/ )
If you want to keep with the strong hauling/towing abilities of the C-30, a great upgrade would be a NV 4500. It's five speeds with a granny low and an overdrive. I'm not sure of the direct bolt in but it should be pretty close. https://www.novak-adapt.com/knowledg...manual/nv4500/ |
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#3 |
Registered User
Join Date: Mar 2010
Location: thomastown mississippi
Posts: 1,261
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Re: 1961 C30 4sp Transmission: swap choices?
That's not an inspection cover, it's a PTO opening.
Your trans is prolly an SM 420. Do you want an overdrive? I don't know if a 261 will push your truck 80 MPH. You may need a double over & a tailwind to get that fast! ![]() A Camaro five speed would prolly be your cheapest way to go, it would bolt to your existing clutch housing with a little modification. A NV 4500 would be a better truck trans but you would need an adapter clutch housing of some type to fit it. If you want better shift ratios a BW T19 would be good w/ a 4 - 1 first gear but your top speed wouldn't change. |
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#4 |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,247
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Re: 1961 C30 4sp Transmission: swap choices?
If you are going to use your C30 as a truck, then the NV4500 would be the best choice. However, the NV4500 bellhousing will not bolt up to your 261. What you would have to do is buy or make a 1" thick adapter plate top adapt the trans to your bellhousing and run a Dodge NV4500. Also the NV4500 as most all OD transmissions have an electronic speedo versus a mechanical speedo as your truck has.
Here is a thread showing using an adapter plate. http://www.67-72chevytrucks.com/vboa...d.php?t=613597 Another option for you would be to change the differential to a later model such as a 14 bolt or a Dana 60 or 70 with 4.10 or 3.73 gears.
__________________
Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE Last edited by Captainfab; 07-21-2018 at 11:35 PM. |
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#5 | ||
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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Re: 1961 C30 4sp Transmission: swap choices?
Quote:
Quote:
I found a reman Chevy/GMC NV 4500 on Ebay and they say "TRANSMISSIONS ARE BUILT TO YOUR VEHICLE SPECIFICATIONS". I'll contact them (or someone like them) to see what they say about mating to a 261. Thanks Michael |
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#6 | |
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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Re: 1961 C30 4sp Transmission: swap choices?
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#7 | |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,247
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Re: 1961 C30 4sp Transmission: swap choices?
How big of a difference a differential change will make depends on exactly what gears are in your differential and what gears to change to.. A C30 likely has 4.57 or 5.14 gears. Changing to 41.0's or 3.73's will make a noticeable change.
Bolting a NV4500 up to a 261 has to do with the bellhousing, not the trans. Unless you are talking about going with the adapter plate as in the link I gave you last night. Quote:
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Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
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#8 |
Registered User
Join Date: Feb 2012
Location: pleasant valley--placerville ca
Posts: 3,039
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Re: 1961 C30 4sp Transmission: swap choices?
find a clark 5sp trans with the (over drive) 5th gear. They don't shift real well but should bolt up. might have to change the clutch disc?
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1961 chevy K10 my build is------------61K10 build |
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#9 |
Registered User
Join Date: Mar 2010
Location: thomastown mississippi
Posts: 1,261
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Re: 1961 C30 4sp Transmission: swap choices?
There was a company down in Lumberton or Purvis Mississippi that made adapter clutch housings, transfer case adapters & output shafts for the Clarks but I have lost the contact info for them.
The Clark has the O/D up front where it belongs, the 4500 in the rear like an overgrown Toyota transmission... |
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#10 | |
Registered User
Join Date: Sep 2008
Location: San Carlos, Ca.
Posts: 3,048
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Re: 1961 C30 4sp Transmission: swap choices?
Quote:
I had one in a '57 3/4 ton Napco truck. It actually shifted really well once I shortened the shifter by a foot. ![]() Just my personal opinion.... the Clark will take more abuse than the 4500. IIRC, it weighed quite a lot more than a 4500 as well.
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Chris '63 k15 long step Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205 ![]() 52" front and 63" rear spring swap D44 / 14bff - disc axles Milemarker 9K and 10.5K hydraulic winches 63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build L29 - 7.4 Vortec Build http://67-72chevytrucks.com/vboard/s...&highlight=L29 |
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#11 | |
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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Re: 1961 C30 4sp Transmission: swap choices?
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#12 | |
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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Re: 1961 C30 4sp Transmission: swap choices?
Quote:
-Michael |
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#13 | |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,247
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Re: 1961 C30 4sp Transmission: swap choices?
The only way to know for sure is to pull the cover and either count the teeth or simply find the tooth counts stamped on the edge of the ring gear. My guess would be that it has 4.10's or possible lower. Have you pulled the cover on your truck's differential to see exactly what you have now?
Quote:
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Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
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#14 |
Chevy addict
Join Date: May 2012
Location: Iron Ridge, WI
Posts: 1,085
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Re: 1961 C30 4sp Transmission: swap choices?
1980s C20 and C30 trucks sometimes had 3:73 or 3:42 gears. My brother has a 1988 single wheel K30 with 3:42 gears. Really nice all around ratio. Also keep in mind you are asking 50 year old technology to go 80mph.. As my father would say "your nuts"
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#15 |
Registered User
![]() Join Date: Mar 2011
Location: Co
Posts: 412
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Re: 1961 C30 4sp Transmission: swap choices?
3.42 gears would not happen in a square body K30 because there is no 3.42 gears for the dana 60 front.
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63 k20 with cummins 4bt, owned sence 1982 |
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#16 |
Chevy addict
Join Date: May 2012
Location: Iron Ridge, WI
Posts: 1,085
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Re: 1961 C30 4sp Transmission: swap choices?
2wd square body do have them and 3:42 is a lot easier to find in the 88 and up trucks
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#17 |
Registered User
![]() Join Date: Mar 2011
Location: Co
Posts: 412
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Re: 1961 C30 4sp Transmission: swap choices?
K30 is not 2wd.
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63 k20 with cummins 4bt, owned sence 1982 |
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#18 |
Registered User
Join Date: Jan 2012
Location: St Louis Mo
Posts: 214
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Re: 1961 C30 4sp Transmission: swap choices?
You could always get a gear vendors overdrive and keep your factory trans and rear axle.
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#19 |
Registered User
Join Date: Jul 2013
Location: Deltona, FL
Posts: 235
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Re: 1961 C30 4sp Transmission: swap choices?
You've got an sm420 in there right now.
If you have the H072 rear axle, you probably have a 5.14 gear set, but you might have 4.57 in there. There's a 4.10 gear set that's the highest GM manufactured for that axle. 4.10's will definitely drop your rpms. Also, the GM literature mentions a 5.83 ratio for that axle. If you happen to have one, sell it to me ![]() If you can find a cheap t5, that's what I would look into for your overdrive because it's an easy swap. Most negative posts about them make them sound like they are built out of plastic, but my brother put one behind the 283 in his '65 Malibu and has thrashed on it for 5 years now. He has a spare that he rebuilt since he assumed the used one he had swapped in wouldn't last, but it's held up fine. I did the nv4500 swap in that link above, and I love it. If you go that route, the most difficult thing will be the adapter plate between the bellhousing and the tranny. I was fortunate to know a friendly machinist that turned mine for cheap. As far as top speed goes, my c10 would do 70 with the 230, nv4500, 12 bolt with 3.73's and 30" tall tires, but that poor little 6 didn't like it much. However, I had woefully neglecting tuning the engine, so that might have helped. A properly tuned 261 should do fine on the freeway with an overdrive and higher gearing. I did swap in a 350 finally, and boy that made all the difference in the world. I loved my old six, but the power increase from the 350 was amazing.
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'66 c10 rust bucket, 350 (pulled and sold, now waiting on 4bt install) nv4500 stock bellhousing, '85 c30 front suspension and 3/4 rear coils with 4.10 H072 rear axle NV4500 install http://67-72chevytrucks.com/vboard/s....php?p=6488778 Suspension update http://67-72chevytrucks.com/vboard/s....php?p=8236775 |
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#20 |
Registered User
Join Date: Jul 2018
Location: Dover, New Hampshire
Posts: 11
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Re: 1961 C30 4sp Transmission: swap choices?
I did the wheel turn, count the drive shaft rev thing and it appears that I have a 5.13 gear. I'm able to find plenty of dually 4.10 rears, but looking for something smaller yet. BTW, all old parts will be kept for potential new owner.
Thanks so much for the info michael |
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#21 |
Registered User
Join Date: Jul 2013
Location: Deltona, FL
Posts: 235
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Re: 1961 C30 4sp Transmission: swap choices?
You aren’t going to find anything smaller than 4.10 for that axle (unless you can find one of the 3.90 sets that was custom made). You don’t need a whole rear axle. The H033, H052, and H072 axles were all banjo style with a removable third member like the Ford 9”. Take out the 8 axle flange bolts that hole the axle to the hub, slide the axles out ~6”, take out the 10 bolts holding the third member in and grunt. Place your 4.10 third in the housing, bolt up the axles, and sell your 5.14 third to a rock crawler on pirate.
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'66 c10 rust bucket, 350 (pulled and sold, now waiting on 4bt install) nv4500 stock bellhousing, '85 c30 front suspension and 3/4 rear coils with 4.10 H072 rear axle NV4500 install http://67-72chevytrucks.com/vboard/s....php?p=6488778 Suspension update http://67-72chevytrucks.com/vboard/s....php?p=8236775 |
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