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#1 |
Registered User
Join Date: Apr 2017
Location: GA
Posts: 151
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Recommended Transmission for 5.7L 350 V8
Hey forum,
considering upgrading my current setup (TH350). I'm torn between the TH400 or the 700r4. I plan on doing some towing and would like to keep the rpms a little lower on the highway. |
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#2 |
Senior Member
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Location: Godley, TX
Posts: 17,964
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Re: Recommended Transmission for 5.7L 350 V8
Pretty much everyone gets torn on this question at some point.
TH400 alone would be an HD upgrade without a reduction in highway rpm. 700R4 would be a reduction in highway rpm without the strength required for an HD application. Assuming you want to stay with an automatic, the only (or perhaps just the best) way to accomplish both goals in a single upgrade is to upgrade to a 4L80E. (or something like that) Another approach that will be more expensive in the long run is to upgrade to TH400 and Gear Vendors over/under drive behind it. But by the time you upgrade all that stuff, you probably could have worked a 4L80E swap... So, what are you going to tow? If a BIG trailer, I'd go with : - TH400 and just accept the highway rpm - TH400 with GV - 4L80E If a tiny trailer: - retain the TH350 and add a GV for your reduced RPM highway use. - or perhaps go with a well built 700R4 (check Bow-tie Overdrives site). What kind of truck? C or K / 10 or 20 Last edited by jocko; 10-24-2018 at 04:54 PM. |
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#3 | |
Registered User
Join Date: Apr 2017
Location: GA
Posts: 151
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Re: Recommended Transmission for 5.7L 350 V8
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#4 |
Senior Member
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Location: Orem, Utah
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Re: Recommended Transmission for 5.7L 350 V8
I would go with a built 700R4 if for the C10 - it's not designed to haul heavy loads anyway, and with a fairly stock 350 you're not likely to overstress it as long as you keep it cool.
BUT - I have to ask what your rear gear is and how heavy the load is. You may be throwing money at a problem that doesn't really exist.
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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#5 | |
Registered User
Join Date: Apr 2017
Location: GA
Posts: 151
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Re: Recommended Transmission for 5.7L 350 V8
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#6 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,720
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Re: Recommended Transmission for 5.7L 350 V8
The GearVendors makes zero sense behind a TH350. The $3000 cost of admission is still limited by the strength of the trans.
A TH700R4 can be built for moderately heavy towing. At least as much as a 1/2 ton truck should be pulling. The 700 is based on the TH350 so the overall strength is about the same but both can be upgraded. IMO, if you need to do a trans and you can't rebuild it yourself I would go to the TH700. I am more of a fan of the TH200 4R, but you are looking at spending a good chunk to get one to hold up under a lot of weight. I'm saving my nickels to get an ExtremeAutomatics TH200 4R for my '69 short step I'm putting a 427 in.
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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#7 | |
Senior Member
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Location: Godley, TX
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
On the other hand, if strength was the goal, why choose a 700R4 at all over a 4L80E? Now here's a question that might help tip the scales toward a 700R4 over a 4L80E... does a 4L80E fit in a low hump truck? Any mods required for a high hump? That's territory many would rather avoid (myself included, if I can help it). I don't know the answer, am curious. |
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#8 |
Moderator
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Location: Cherryville, NC
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Re: Recommended Transmission for 5.7L 350 V8
4L80E behind a 350 in 67 low hump cab...no issues with clearances in my build....
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Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox ![]() ![]() ![]() |
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#9 |
Senior Member
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Location: Godley, TX
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Re: Recommended Transmission for 5.7L 350 V8
thanks, good to know
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#10 | |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,720
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
If I wanted a 4L80E in a truck, I would buy a 2500HD that had one it along with a 6.0 V8 and swap it all in using factory electronics. The aftermarket trans controller is a big expense with the 4L80. It won't be long before we don't talk about these 4 speeds at all as the 6 and 8 speed trans will start to be the more common swap when price starts coming down and that will be the bomb. In my own truck I plan on running the TH200 4R. My reasoning is that it has the most logical gear spread of any of the 4 speed automatics. The TH700 has too low a first gear and too wide a spread between first and second from a total performance standpoint (Once again, these are all my opinons...) and the 4L80E suffers from insufficient first gear, IMO. But the TH200 4R has an almost ideal split on the 1-2 gears and more overdrive than either of the other two. But the drawback is cost. In my case, it's worth the $3500 or so that it will cost to make this happen. As usual, YMMV.
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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#11 |
Senior Member
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Location: Godley, TX
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Re: Recommended Transmission for 5.7L 350 V8
I like your work best for least money approach. And as I read back thru my comment I realize I mixed some of my own truck's considerations into the OP's discussion (i.e. moving eng fwd or t-case backward, etc - that's a 4x4 consideration (i.e. mine), not the OP's (sorry about that Auroch!) I like the 2004R also - specifically because the 1st gear is not as deep, but also because of its overall dimensions, not sure why it always seems to get less press than the 700 most of the time. Have you looked at the high perf 2004Rs at Bowtie Overdrives? I haven't looked recently, but I don't recall them being much more expensive than the 700s.
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#12 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,720
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Re: Recommended Transmission for 5.7L 350 V8
I'm putting an L36 427 in my truck with a Nitrous grind hydraulic roller which should be 450hp and 500lb/ft so a trans that will hold up runs around $3500 by the time you are all in.
Bowtie Overdrives does not have as good a reputation as Extreme does. And my buddy has an Extreme that had issues when he got it (as autos can and will have) and they were very prompt in taking care of it including shipping both ways. You mentioned TV cable adjustment earlier, and just to add to the knowledge in this post check out constant pressure valve bodies. You still need to have TV adjusted correctly for shifting, but the eliminate trans failure from misadjusted TV. http://www.tciauto.com/tc/valve-bodi...-pressurehtml/
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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#13 | |
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Join Date: Apr 2017
Location: GA
Posts: 151
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Re: Recommended Transmission for 5.7L 350 V8
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#14 |
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Join Date: Jan 2014
Location: SoCal
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Re: Recommended Transmission for 5.7L 350 V8
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#15 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: Recommended Transmission for 5.7L 350 V8
TH350's are stouter than people give them credit for. Even in stock form.
What RPM are you turning? Most people nowadays are spoiled with modern EFI and OD transmissions. If you're worried about parts and longevity... a 350 with a TH350 is made to take the RPM's and live. However, your wallet may not be able to with fuel consumption. Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#16 | |
Registered User
Join Date: Apr 2017
Location: GA
Posts: 151
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
So about the RPMs, it's my fault, I have a lead foot... I push the truck too much on the interstate. I don't have a tach on my truck yet, by the sound, I'm guessing I must be doing 4000 rpm on average; that sound right? |
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#17 |
Registered User
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Location: Jurupa Valley, Ca
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Re: Recommended Transmission for 5.7L 350 V8
You may really want to find out what gear ratio you have before doing anything. According to the documentation I see, a 70 C10 with the optional 350 and TH350 trans, the standard ratio is 3.07. You shouldn't be seeing 4000 RPM on the freeway unless your driving 90+
Also something to consider is you may never recoup the money to put a OD automatic in improved gas mileage unless you drive a lot. I put a 2004R in my truck since I have 4.10 gears. My mileage improved from about 9.5 to 13.5 MPG.
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
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#18 | |
Senior Member
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Location: Studio City, Calif.
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
But if he is guessing 4000 RPM then he either has a much lower ratio or he is a madman. -BA
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 10-25-2018 at 04:36 PM. |
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#19 | |
Registered User
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Location: Jurupa Valley, Ca
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Re: Recommended Transmission for 5.7L 350 V8
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
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#20 | |||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
![]() I don't tow or haul with it... except haul a$$. ![]() Gary
__________________
'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
Quote:
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#21 | |
Senior Member
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Location: Studio City, Calif.
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Re: Recommended Transmission for 5.7L 350 V8
Quote:
I have 3.73 gears but with a manual and 31" tires and I spin 2500 at 60. -BA
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
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#22 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: Recommended Transmission for 5.7L 350 V8
I have 26" tall tires.
![]() Gary
__________________
'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
Quote:
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#23 |
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Join Date: Aug 2009
Location: Bowser
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Re: Recommended Transmission for 5.7L 350 V8
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#24 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
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Re: Recommended Transmission for 5.7L 350 V8
T350's are good. We have have one our 64 GTO with a destroked 455. It has pulled 450 + pound feet of torque on several chassis dyno's and runs in the low 11's. We only have run it on street tires and no trans brake. Which i am sure has keep it alive. At 3200 lbs it is lighter than your truck but I wouldn't think twice about running one with your plan.
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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