Replace the existing TH350 with another TH350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

The Swed · 04-26-2016, 06:10 PM

Sure seems like the engine Revs are high at 65... is this normal?

boogieman1 · 04-26-2016, 06:27 PM

What is your differential gear ratio?

SS Tim · 04-26-2016, 06:34 PM

Unless it was built with an optional lower ratio your truck should have 4.10 gears.

Plugging in a nominal 30" tire diameter it looks to be 2985 rpm @ 65 mph.

http://www.summitracing.com/expertad...tio-calculator

All depends on what your definition of "normal" is. When new it was. To people raised on double overdriven engines it sounds like imminent destruction.

Are you using your 3/4 ton truck as a truck or just a cool looking car replacement?

The Swed · 04-26-2016, 06:39 PM

It's Dana 60... and it's in a stock C20...

The Swed · 04-26-2016, 06:40 PM

SS Tim as a truck!

SS Tim · 04-26-2016, 07:28 PM

Ifyou are using it as a truck then you will probably need the gear it has. So then the basic question comes back to keeping the TH350 replacing it with a 200R4/700R4 or adding a gear vendors overdrive. If it is limited mileage driven keep the TH350. If you want to drive it a LOT, a well set up four speed auto can be benficial in lower rpm and higher road speeds. But it does take money and knowledge, anything less is false economy. A gear vendors would be a great choice but they can be expensive. However the usable five speed your TH350 would become is great with high drag or heavy loads like camper or trailer.

**DeadheadNM** · 04-26-2016, 09:56 PM

May be worthwhile checking the rpm with a tach to see where you stand at 65 mph. I really like driving at highway speed in my 700r4 HO52 equipped K20 but could get by with a TH350. Last night I was driving my TH400 HO72 equipped C30 at speeds up to 70 mph and it was cruising fine, didn't sound too wound up as for rpms. If you need a new tranny and don't anticipate much long distance hauling I'd keep it simple and rebuild the TH350.

mike16 · 04-26-2016, 11:02 PM

was a th350 available in c20's ? I have 373's in my truck and it screams at 70 plus mph. very usefull on the few occassions I hual something. as a daily driver it cost a plenty.

I wouls put a 400 in it or an od automatic. but remember you got a nice choice of gear ratios for that dana sixty

The Swed · 04-27-2016, 03:46 PM

Okay, I'm sticking with the TH350... thanks for all the input!

04-26-2016, 06:10 PM	#1
The Swed Registered User Join Date: Jan 2015 Location: West Haven, Utah Posts: 135	Replace the existing TH350 with another TH350 Sure seems like the engine Revs are high at 65... is this normal? __________________ 1970 C20 350/TH350, LB God Bless our Troops

04-26-2016, 06:27 PM	#2
boogieman1 Registered User Join Date: Feb 2016 Location: indianapolis, in Posts: 46	Re: Replace the existing TH350 with another TH350 What is your differential gear ratio? __________________ '72 chevy C20 Cheyenne Super

04-26-2016, 06:34 PM	#3
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,503	Re: Replace the existing TH350 with another TH350 Unless it was built with an optional lower ratio your truck should have 4.10 gears. Plugging in a nominal 30" tire diameter it looks to be 2985 rpm @ 65 mph. http://www.summitracing.com/expertad...tio-calculator All depends on what your definition of "normal" is. When new it was. To people raised on double overdriven engines it sounds like imminent destruction. Are you using your 3/4 ton truck as a truck or just a cool looking car replacement? __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

04-26-2016, 06:39 PM	#4
The Swed Registered User Join Date: Jan 2015 Location: West Haven, Utah Posts: 135	Re: Replace the existing TH350 with another TH350 It's Dana 60... and it's in a stock C20... Attached Images __________________ 1970 C20 350/TH350, LB God Bless our Troops

04-26-2016, 06:40 PM	#5
The Swed Registered User Join Date: Jan 2015 Location: West Haven, Utah Posts: 135	Re: Replace the existing TH350 with another TH350 SS Tim as a truck! __________________ 1970 C20 350/TH350, LB God Bless our Troops

04-26-2016, 07:28 PM	#6
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,503	Re: Replace the existing TH350 with another TH350 Ifyou are using it as a truck then you will probably need the gear it has. So then the basic question comes back to keeping the TH350 replacing it with a 200R4/700R4 or adding a gear vendors overdrive. If it is limited mileage driven keep the TH350. If you want to drive it a LOT, a well set up four speed auto can be benficial in lower rpm and higher road speeds. But it does take money and knowledge, anything less is false economy. A gear vendors would be a great choice but they can be expensive. However the usable five speed your TH350 would become is great with high drag or heavy loads like camper or trailer. __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

04-26-2016, 09:56 PM	#7
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,348	Re: Replace the existing TH350 with another TH350 May be worthwhile checking the rpm with a tach to see where you stand at 65 mph. I really like driving at highway speed in my 700r4 HO52 equipped K20 but could get by with a TH350. Last night I was driving my TH400 HO72 equipped C30 at speeds up to 70 mph and it was cruising fine, didn't sound too wound up as for rpms. If you need a new tranny and don't anticipate much long distance hauling I'd keep it simple and rebuild the TH350. __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland

04-26-2016, 11:02 PM	#8
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: Replace the existing TH350 with another TH350 was a th350 available in c20's ? I have 373's in my truck and it screams at 70 plus mph. very usefull on the few occassions I hual something. as a daily driver it cost a plenty. I wouls put a 400 in it or an od automatic. but remember you got a nice choice of gear ratios for that dana sixty

04-27-2016, 03:46 PM	#9
The Swed Registered User Join Date: Jan 2015 Location: West Haven, Utah Posts: 135	Re: Replace the existing TH350 with another TH350 Okay, I'm sticking with the TH350... thanks for all the input! __________________ 1970 C20 350/TH350, LB God Bless our Troops



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