What yr 700R4 ?

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What yr 700R4 ?

Postby mainman22 » Fri Apr 10, 2015 1:17 am

What yr of 700R4 is the best yr to put in my 71 vega? Thanks in advance for input....
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1971 Chevrolet Vega


Re: What yr 700R4 ?

Postby Smiley » Fri Apr 10, 2015 3:35 am

Unless you plan on doing a power tour I would just use a 3 speed auto for racing or cruising around town, they are cheap and simple.
71 Vega's will need some reshaping (BFH massaging) of the trans tunnel around the firewall for V8 transmissions.
1986 and up 700R4's are good.
700's are longer so the driveshaft will need to be shorter.
700's have a different rear mount location so the crossmember will need to be moved back more than 350's.
700's use an electric solenoid to activate the lockup, this will require a controller or at least some basic wiring and pressure switches.
700's and 200's use TV cables that look like the older passing gear cables but require very precise adjustment and that the OEM pivot to throttle shaft geometry be used.
So if you use a universal aftermarket performance carburetor you must add the cable pivot at the same location as a factory carb or throttle body and then adjust the TV cable tension to specs.
I swapped a TH350 for 86 700R4 to get overdrive and lockup and I did not like the 1st to 2nd RPM drop compared to the TH350.
I was driving 50 miles a day with about half on the highway so I recouped the time and money.
The 2004R trans has closer ratios from 1st to 2nd and shares most dimensions with the TH350 making it an easier swap.
A 3 speed TH350 with a 3.42, 3.23 or 3.08 works well with a healthy 350 V8 in an early Vega.
A 4.10 rear axle gear with the 3.08 first gear of the 700R4 will give way too much torque multiplication for a 24" street tire.
What do you plan to use the car for most of the time ?
Last edited by Smiley on Sun Apr 12, 2015 6:53 am, edited 1 time in total.
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Re: What yr 700R4 ?

Postby mainman22 » Fri Apr 10, 2015 2:07 pm

Thank You, Im planning on cruising it, maybe a 150 one way trip. That will get me to central Oregon or the coast, I have 205 50 15 on the front and 225 50 15 on the rear. I have a .60 over 350 with a 272H cam and 10.5 to 1 ..... rear end is a 4.10 gear.... Its just gonna be a play toy.... anymore info is appreciated..
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Re: What yr 700R4 ?

Postby Smiley » Fri Apr 10, 2015 6:21 pm

what parts do you have already as far as carb, intake exhaust, headers ?
do you have a trans yet ? was the car a manual trans originally?
so your rear tires are about 24" tall ?
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Re: What yr 700R4 ?

Postby mainman22 » Sat Apr 11, 2015 2:26 am

Have a 650 Holley Vac, secondaries. Edelbrock performer intake. NO exhaust yet Well I have 40 series flow masters. Im thinking a short header with thick flanges, My Brother builds tranny's so he said he will have me a turbo 350 by end of the day sunday. its a factory stick shift car
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Re: What yr 700R4 ?

Postby Monza Harry » Sat Apr 11, 2015 9:01 am

The 2004R is dimensional similar to the THM350 except the rear trans mount is further back (around 6" or so) very similar looking to a THM400 but not the same number IIRC. The 2004R also accepts the same driveshaft yolk and OAL (over all length). The 2004R's 0.67:1 OD Ratio with your approx. stock height rear and your 4.10 would be a good cruise gear for the highway (2.75) as long as your not going crazy with the cam, this will put you near 2600/2800 RPM at 100Kph (60MPH) Harry
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Re: What yr 700R4 ?

Postby 67shovel » Sat Apr 11, 2015 9:55 am

I building a 73 V8 Vega wagon and I picked the 700r4 trans so I could/would drive it more. Getting out on the freeway without an overdrive is painful! I think the overdrive is worth the hassle of the install. Granted, I haven't fired it up yet so Smileys comment on the 1st to 2nd shift drop caught my attention. I'm getting close to driving so I'll report back. I went with Sanderson shorty headers on mine after trying hooker and Don Hardy headers. Hookers hang into the wheel wells and the Don Hardys point to the rockers. They both hang down not giving much ground clearance so I went with shorties. For perforamce you should use the headers IMHO.

Roger
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Re: What yr 700R4 ?

Postby Smiley » Sun Apr 12, 2015 6:06 am

10.5 to 1, what heads are on it ?

4.11 rear + 24" tire @65 mph = 3740 RPM
3.08 rear + 26" tire @65 mph = 2587 RPM
4.11x .70 + 24" tire @65 mph = 2484 RPM
If you plan on buying tires you might want to go to a 26" rear tire, this will drop about 300 rpm at 65
with a 3 speed auto I would use a 3.08 rear end gear, this will drop about 1000 rpm at 65
.70 Overdrive will drop 1400 from 3rd to 4th at 65
so a 4 speed auto would only run 100 rpm less than the 3.08 with 26" tires and a TH350
If you plan on a lot of highway trips the overdrive will payoff eventually but gas being cheap it may not be worth it.
71 to 73 gas tanks are only about 11 gallons.
The fuel gage may be off a bit, first time I filled mine it said 1/4 of a tank but took over 10 gallons.
Change the dash bulbs before going on a trip driving at night.

The 200-4R first gear is halfway in between the 350 and the 700 so the 1-2 drop is smaller,
yet the overdrive on the 200 is actually higher.
GM ... 1st . 2nd .3rd . 4th
Pglide 1.76 1.00
TH350 2.52 1.52 1.00
TH400 2.48 1.48 1.00
2004R 2.74 1.57 1.00 0.67
700R4 3.06 1.62 1.00 0.70
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Re: What yr 700R4 ?

Postby mainman22 » Mon Apr 13, 2015 1:22 am

Thanks for all the input guys. Its just gonna be a toy, hardly any highway driving.... Ill post pics when painted and body and paint done. But still looking for a rear spoiler,
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Re: What yr 700R4 ?

Postby T-FATTY » Mon Apr 13, 2015 5:16 am

I want to do the 200r4 swap as well with 3:73 gears. I had this combo in a 1985 Monte Carlo SS and it was great all around. My current set up is getting old, turbo 350 with 4:56s, ok around town but don't even think of getting on the highway.
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