700R4 for 73-80 question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

79stepside_SS400 · 10-29-2006, 09:39 PM

i was plannin on installing a 700R4 trans in my truck sometime soon. the trans thats in it now is a Th350 dont know if its short/long tail. is there any modifications this swap will require? cross member? shortened driveshaft? yoke? etc...

Jonboy · 10-29-2006, 10:01 PM

The driveshaft will need to be shortened. You can use your original crossmamber, but you may need to drill new holes for it. The shift linkage will need to be adjusted a bit to engage first. Also, you will most likely need to make the lockup torque converter work. I sea a really cool kit from Ron Francis wiring www.ronfrancis.com in the new Hot Rod Magazine this month, or you can use a painless wiring kit or there are instructions on www.73-87.com as well.

Russell · 10-29-2006, 11:38 PM

Driveshaft should be the same length between your TH350 and the 700r4, it was the earlier trucks that got the short tail TH350, at which point you'd just swap in a 2004r instead.

I was able to use my original crossmember, and as mentioned, just had to drill 4 new holes on the frame rails. As far as the shift linkage goes, I just set mine up like any other truck, and just couldn't access the last gear.

The lockup stuff is easy, find any one of these trucks from 83-86 with a 700r4, and pull the stock lockup stuff. Need to grab the brake light switch, and the vac switch on the firewall by the brake booster. Should be a single wire hookup at that point, just slip one wire onto an ignition power source on the fuse box.

When looking to buy, keep in mind that many newer 700r4s use a VSS instead of a mechanical speedo cable, make sure that whichever you buy has the speedo cable for your truck to bolt up to.

79stepside_SS400 · 10-30-2006, 02:51 AM

im not sure whether my 350 is short or long, it came out of my dad's unoriginal '56 nomad. my 700R4 is out of an '88 astro. the wiring harness for the tranny is the same for camaros right?

Jonboy · 10-30-2006, 08:22 AM

yes, it should be.

Russell · 10-30-2006, 08:23 AM

Easy enough to figure out the length of the tranny -- Just find a measuring tape and measure the length of the tailhousing, from where it bolts onto the tranny casing up to where the slip yolk ends.

An 88 astrovan will likely have an electric VSS, and the wiring harness for the tranny depends on the year of the car, if it is EFI, it won't work, if it is carbed, it will.

10-29-2006, 09:39 PM	#1
79stepside_SS400 Registered User Join Date: Oct 2006 Location: waipahu Posts: 23	700R4 for 73-80 question i was plannin on installing a 700R4 trans in my truck sometime soon. the trans thats in it now is a Th350 dont know if its short/long tail. is there any modifications this swap will require? cross member? shortened driveshaft? yoke? etc...

10-29-2006, 10:01 PM	#2
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: 700R4 for 73-80 question The driveshaft will need to be shortened. You can use your original crossmamber, but you may need to drill new holes for it. The shift linkage will need to be adjusted a bit to engage first. Also, you will most likely need to make the lockup torque converter work. I sea a really cool kit from Ron Francis wiring www.ronfrancis.com in the new Hot Rod Magazine this month, or you can use a painless wiring kit or there are instructions on www.73-87.com as well.

10-29-2006, 11:38 PM	#3
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: 700R4 for 73-80 question Driveshaft should be the same length between your TH350 and the 700r4, it was the earlier trucks that got the short tail TH350, at which point you'd just swap in a 2004r instead. I was able to use my original crossmember, and as mentioned, just had to drill 4 new holes on the frame rails. As far as the shift linkage goes, I just set mine up like any other truck, and just couldn't access the last gear. The lockup stuff is easy, find any one of these trucks from 83-86 with a 700r4, and pull the stock lockup stuff. Need to grab the brake light switch, and the vac switch on the firewall by the brake booster. Should be a single wire hookup at that point, just slip one wire onto an ignition power source on the fuse box. When looking to buy, keep in mind that many newer 700r4s use a VSS instead of a mechanical speedo cable, make sure that whichever you buy has the speedo cable for your truck to bolt up to. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

10-30-2006, 02:51 AM	#4
79stepside_SS400 Registered User Join Date: Oct 2006 Location: waipahu Posts: 23	Re: 700R4 for 73-80 question im not sure whether my 350 is short or long, it came out of my dad's unoriginal '56 nomad. my 700R4 is out of an '88 astro. the wiring harness for the tranny is the same for camaros right?

10-30-2006, 08:22 AM	#5
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: 700R4 for 73-80 question yes, it should be.

10-30-2006, 08:23 AM	#6
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: 700R4 for 73-80 question Easy enough to figure out the length of the tranny -- Just find a measuring tape and measure the length of the tailhousing, from where it bolts onto the tranny casing up to where the slip yolk ends. An 88 astrovan will likely have an electric VSS, and the wiring harness for the tranny depends on the year of the car, if it is EFI, it won't work, if it is carbed, it will. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)



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