700-r4 decision - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Solver · 10-17-2006, 12:37 AM

I have a 72 3/4 ton with a 402 engine 400 tranny and 4:10 rear end. I like driving the truck but at 65 mph the thing is turning around 3500 rpm. I have a 700r4 I picked up at a swap meet. Do you think it would be worth it to swap it in. Any ideas what I would be turning for rpms at 60-65 mph.Besides shortening the drive shaft,shifting the tranny cross member,tranny mount and tranny linkage hookup (tv Cable)
what other problems or unexpected pieces am I going to need. Will the current driveshaft bolt up splines wise. Just hate to start the project and be dissappointed with the results or the cost of unanticipated part needs. Thanks
Solver

krue · 10-17-2006, 12:47 AM

The 400 has a yoke while the 700r uses the same splines as the TH350's iirc.

sweet70beast · 10-17-2006, 01:08 AM

I did this same thing in a 72 Gmc 3/4 with a 402 a few years ago. The drive shaft front one will need to be shortened about 2 inches, the trans mount from a th350 will bolt right on the 700, the hardest part about the swap is getting the tv cable hooked up right. The converter will bolt up to the th350 holes in the flexplate.

qksilver · 10-17-2006, 08:24 AM

The only concern would be is the can the trans handle the BB especially if you tow with it

70GMCer · 10-17-2006, 02:03 PM

I'm going to be doing this same swap. I have did some research on beefing up the 700r4. I have read that you should change the stock servo to a Corvette type and also change the booster to .500 size. From what I have found, these are cheap parts and easy to change. I also plan on changing the converter to around 2000 stall. Here's a parts sight that has the best prices I've found. I haven't bought from them as yet.

http://www.bulkpart.com/Merchant2/me...&Store_Code=2s

You are also going to have to do some lockup converter wiring on this trans.

Longhorn Man · 10-17-2006, 03:16 PM

need to make sure the bellcrank on the carb is of the right diameter and shape, the rate of pull and sensitivity of it needs to be dead on for tranny life. you'll also need a lockup controller too.

Texasdeere · 10-17-2006, 03:27 PM

With a 4.10 rear and 29 inch tires about 2160 in 4th with lockup

Your tires are probably a little taller that that though on a C20.

Here is a great gear calculator:

http://www.xse.com/leres/ss/calculator.html

**VetteVet** · 10-17-2006, 04:31 PM

Here's a site I like. It has a lot of info and a gear ratio chart at the bottom.http://www.transmissioncenter.net/700r4.htm

67ChevyRedneck · 10-17-2006, 04:39 PM

I like mine, but I'm on the second one.... as longhornman said... set-up is absolutely CRUCIAL in a 700R4.

Werewolf · 10-17-2006, 06:11 PM

Biggest concern is, can a used TH-700 in potentially unknown operating condition stand up long to big block torque? If your engine is more or less stock, it should hold up for a while. As long as you're not abusive towards it. Classically, though, TH-700's just can't be built up as strong as a 350 or 400.

A TH-700's overdrive ratio is .8 to 1. 3500@65 seems awfully high to me, and I don't know that .8:1 ratio is going to bring it down to 2100 @ 65.

**kwmech** · 10-17-2006, 09:33 PM

Actually the 700 has overdrive of 28% so the multiplier would be .72--- Your 3500 rpm times .72 would theoretically come down to 2520, without the lock-up. A stronger set-up would be adding on a Gear Vendor unit that has a 22% overdrive.

Texasdeere · 10-17-2006, 09:38 PM

TH700R4 4-Speed Automatic Transmission Gear Ratios: 3.06, 1.63, 1.00, 0.70 (1st through 4th)

The overdrive is pretty steep on these.

With the lockup not engaged the rpms will be higher. These trannys can be set up with no lock up or even a hydraulic lockup. (no wires) As everyone has said before proper cable set up is a must. The 700R4 is a good strong tranny but not as strong as the TH400. I would think that a stock big block shouldn't hurt it with normal use. If you pull with your truck just use third gear 1.00:1 for pulling. If you are going big horse power and torque, especially torque a TH400 with a Gear Venders overdrive is the way to go. I think the Gear Vender overdrives are over $2500

.

Sorry, I'll stop now

Texasdeere · 10-17-2006, 09:39 PM

You beat me to it kwmech. I just type too slow.

Werewolf · 10-18-2006, 07:19 AM

I could just say I hit the wrong number key, but I won't. Oops! Maybe the 200 had a .8 overdrive. Or maybe I'm just dumb.

67ChevyRedneck · 10-18-2006, 08:02 AM

700R4 is .70 to 1 and a 4l60E is .67 to 1.

10-17-2006, 12:37 AM	#1
Solver Registered User Join Date: May 2000 Location: Storm Lake, Ia Posts: 1,449	700-r4 decision I have a 72 3/4 ton with a 402 engine 400 tranny and 4:10 rear end. I like driving the truck but at 65 mph the thing is turning around 3500 rpm. I have a 700r4 I picked up at a swap meet. Do you think it would be worth it to swap it in. Any ideas what I would be turning for rpms at 60-65 mph.Besides shortening the drive shaft,shifting the tranny cross member,tranny mount and tranny linkage hookup (tv Cable) what other problems or unexpected pieces am I going to need. Will the current driveshaft bolt up splines wise. Just hate to start the project and be dissappointed with the results or the cost of unanticipated part needs. Thanks Solver __________________ 1972 Cheyenne Super 20 LWB-Blue 1972 Cheyenne Super 10 LWB-Black 1972 Cheyenne Super 10 LWB-Red 1972 Cheyenne Super 10 LWB-green 1972 GMC 4x4 LWB-White 1971 Cheyenne 10 LWB-Ochre 1971 Cheyenne 20 Longhorn-Copper 1971 Cheyenne 20 Longhorn-Black 1969 Custom 10 LWB-lt blue 1968 GMC 3/4 ton-green 1968 1/2 ton swb stepside-silver 1967 Chevrolet CST 10 LWB-green 1967 Chevrolet custom 20 LWB-Maroon

10-17-2006, 12:47 AM	#2
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: 700-r4 decision The 400 has a yoke while the 700r uses the same splines as the TH350's iirc. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

10-17-2006, 01:08 AM	#3
sweet70beast Registered User Join Date: Sep 2006 Location: Shelley Idaho Posts: 876	Re: 700-r4 decision I did this same thing in a 72 Gmc 3/4 with a 402 a few years ago. The drive shaft front one will need to be shortened about 2 inches, the trans mount from a th350 will bolt right on the 700, the hardest part about the swap is getting the tv cable hooked up right. The converter will bolt up to the th350 holes in the flexplate.

10-17-2006, 08:24 AM	#4
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: 700-r4 decision The only concern would be is the can the trans handle the BB especially if you tow with it

10-17-2006, 02:03 PM	#5
70GMCer Senior Member Join Date: Apr 2005 Location: Joppa, Maryland Posts: 4,408	Re: 700-r4 decision I'm going to be doing this same swap. I have did some research on beefing up the 700r4. I have read that you should change the stock servo to a Corvette type and also change the booster to .500 size. From what I have found, these are cheap parts and easy to change. I also plan on changing the converter to around 2000 stall. Here's a parts sight that has the best prices I've found. I haven't bought from them as yet. http://www.bulkpart.com/Merchant2/me...&Store_Code=2s You are also going to have to do some lockup converter wiring on this trans. __________________ 1997 GMC Sierra Ext 1965 Mustang

10-17-2006, 03:16 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 700-r4 decision need to make sure the bellcrank on the carb is of the right diameter and shape, the rate of pull and sensitivity of it needs to be dead on for tranny life. you'll also need a lockup controller too.

10-17-2006, 03:27 PM	#7
Texasdeere Registered User Join Date: Sep 2006 Location: League City, Texas Posts: 732	Re: 700-r4 decision With a 4.10 rear and 29 inch tires about 2160 in 4th with lockup Your tires are probably a little taller that that though on a C20. Here is a great gear calculator: http://www.xse.com/leres/ss/calculator.html Last edited by Texasdeere; 10-17-2006 at 03:33 PM.

10-17-2006, 04:31 PM	#8
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: 700-r4 decision Here's a site I like. It has a lot of info and a gear ratio chart at the bottom.http://www.transmissioncenter.net/700r4.htm __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

10-17-2006, 04:39 PM	#9
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	Re: 700-r4 decision I like mine, but I'm on the second one.... as longhornman said... set-up is absolutely CRUCIAL in a 700R4. __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! Last edited by 67ChevyRedneck; 10-17-2006 at 04:40 PM.

10-17-2006, 06:11 PM	#10
Werewolf Woof? Join Date: Jun 2005 Location: Raleigh, NC Posts: 276	Re: 700-r4 decision Biggest concern is, can a used TH-700 in potentially unknown operating condition stand up long to big block torque? If your engine is more or less stock, it should hold up for a while. As long as you're not abusive towards it. Classically, though, TH-700's just can't be built up as strong as a 350 or 400. A TH-700's overdrive ratio is .8 to 1. 3500@65 seems awfully high to me, and I don't know that .8:1 ratio is going to bring it down to 2100 @ 65. __________________ 1968 LWB CST BB 2004 Avalanche Z71 LT3. 2003 S-10 ZR2 (hers). 1997 Astro 1992 Caprice wagon, 500k stock miles. Nursing wounds after a bad wreck. 1997 Saturn - need gas mileage from something!

10-17-2006, 09:33 PM	#11
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,482	Re: 700-r4 decision Actually the 700 has overdrive of 28% so the multiplier would be .72--- Your 3500 rpm times .72 would theoretically come down to 2520, without the lock-up. A stronger set-up would be adding on a Gear Vendor unit that has a 22% overdrive.

10-17-2006, 09:38 PM	#12
Texasdeere Registered User Join Date: Sep 2006 Location: League City, Texas Posts: 732	Re: 700-r4 decision TH700R4 4-Speed Automatic Transmission Gear Ratios: 3.06, 1.63, 1.00, 0.70 (1st through 4th) The overdrive is pretty steep on these. With the lockup not engaged the rpms will be higher. These trannys can be set up with no lock up or even a hydraulic lockup. (no wires) As everyone has said before proper cable set up is a must. The 700R4 is a good strong tranny but not as strong as the TH400. I would think that a stock big block shouldn't hurt it with normal use. If you pull with your truck just use third gear 1.00:1 for pulling. If you are going big horse power and torque, especially torque a TH400 with a Gear Venders overdrive is the way to go. I think the Gear Vender overdrives are over $2500 . Sorry, I'll stop now Last edited by Texasdeere; 10-17-2006 at 09:43 PM.

10-17-2006, 09:39 PM	#13
Texasdeere Registered User Join Date: Sep 2006 Location: League City, Texas Posts: 732	Re: 700-r4 decision You beat me to it kwmech. I just type too slow.

10-18-2006, 07:19 AM	#14
Werewolf Woof? Join Date: Jun 2005 Location: Raleigh, NC Posts: 276	Re: 700-r4 decision I could just say I hit the wrong number key, but I won't. Oops! Maybe the 200 had a .8 overdrive. Or maybe I'm just dumb. __________________ 1968 LWB CST BB 2004 Avalanche Z71 LT3. 2003 S-10 ZR2 (hers). 1997 Astro 1992 Caprice wagon, 500k stock miles. Nursing wounds after a bad wreck. 1997 Saturn - need gas mileage from something!

10-18-2006, 08:02 AM	#15
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	Re: 700-r4 decision 700R4 is .70 to 1 and a 4l60E is .67 to 1. __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications!



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