TH350 to 700R4 Driveshaft - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bad72c10 · 04-08-2007, 09:28 PM

Hey guys, I have a TH350 with a 9" tailshaft in the truck now, so I should be able to reuse the driveshaft for the 700r4 with no modifications, correct?

Also, when I look up a transmission mount, it has three holes, yet the crossmember only has two, how does that work?

And lastly, does anyone know where I can get just a single speedo gear?? BTO only sells a $52.00 complete set

Thanks for your help, Justin

dave2953 · 04-08-2007, 09:43 PM

The TCI website shows them to be nearly identical in length. Your trans. is 30 11/16 and the 700R4 is 30 3/4, so you should be able to use your current driveshaft. I'm not sure about the mount or the speedo. I'm sure someone else will chime in and let you know.

lamar · 04-08-2007, 09:49 PM

I went from Turbo 350 to 700R4 and I had to have my drive shaft cut and rebalanced. Also had to relocate the trans mount.

Mixup · 04-08-2007, 11:08 PM

I had the 9" tailshaft 350 and the shaft worked fine. The speedo worked to just had to change the gears to match the tire size and rear ratio. Crossmember has to move back to match the 700r4 mount.

bad72c10 · 04-08-2007, 11:49 PM

Thanks Mixup, I was sure it would work, but it is good to hear from someone who has done it. I knew the X-member had to move back, but the holes where you bolt the tranny mount to the x-member has 2 holes, yet the mounts that I see have 3 holes for bolts. does it work anyway?

cooters · 04-08-2007, 11:57 PM

just go to a tranny shop, the mounts come in 1 ,2,bolt holes or even a stud. Get the one you need from the tranny shop is usually the cheapest and they should stock them all.

Mixup · 04-09-2007, 05:27 PM

Mine has the 2 bolts that hold the mount to the trans and 2 bolts from the crossmember to the mount. You might have to get a different mount.

BACKYARD88 · 04-09-2007, 05:45 PM

You should be able to buy the speedo gear from a GM dealer individually.

04-08-2007, 09:28 PM	#1
bad72c10 Registered User Join Date: Dec 2006 Location: New Mexico Posts: 88	TH350 to 700R4 Driveshaft Hey guys, I have a TH350 with a 9" tailshaft in the truck now, so I should be able to reuse the driveshaft for the 700r4 with no modifications, correct? Also, when I look up a transmission mount, it has three holes, yet the crossmember only has two, how does that work? And lastly, does anyone know where I can get just a single speedo gear?? BTO only sells a $52.00 complete set Thanks for your help, Justin __________________ '72 C/10 SWB 355/ broken TH350 and 3.07s Soon to be 355/700r4 and 3.73s

04-08-2007, 09:43 PM	#2
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: TH350 to 700R4 Driveshaft The TCI website shows them to be nearly identical in length. Your trans. is 30 11/16 and the 700R4 is 30 3/4, so you should be able to use your current driveshaft. I'm not sure about the mount or the speedo. I'm sure someone else will chime in and let you know. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

04-08-2007, 09:49 PM	#3
lamar Registered User Join Date: Apr 2004 Location: Covington,Ga Posts: 453	Re: TH350 to 700R4 Driveshaft I went from Turbo 350 to 700R4 and I had to have my drive shaft cut and rebalanced. Also had to relocate the trans mount. __________________ 72 C-10

04-08-2007, 11:08 PM	#4
Mixup Registered User Join Date: Jan 2002 Location: Henderson, NV Posts: 358	Re: TH350 to 700R4 Driveshaft I had the 9" tailshaft 350 and the shaft worked fine. The speedo worked to just had to change the gears to match the tire size and rear ratio. Crossmember has to move back to match the 700r4 mount. __________________ 1980 Chevy Shortbed Pickup 1969 Z28 engine Turbo 350

04-08-2007, 11:49 PM	#5
bad72c10 Registered User Join Date: Dec 2006 Location: New Mexico Posts: 88	Re: TH350 to 700R4 Driveshaft Thanks Mixup, I was sure it would work, but it is good to hear from someone who has done it. I knew the X-member had to move back, but the holes where you bolt the tranny mount to the x-member has 2 holes, yet the mounts that I see have 3 holes for bolts. does it work anyway? __________________ '72 C/10 SWB 355/ broken TH350 and 3.07s Soon to be 355/700r4 and 3.73s

04-08-2007, 11:57 PM	#6
cooters Senior Member Join Date: Oct 2006 Location: Edmonton Alberta Posts: 458	Re: TH350 to 700R4 Driveshaft just go to a tranny shop, the mounts come in 1 ,2,bolt holes or even a stud. Get the one you need from the tranny shop is usually the cheapest and they should stock them all.

04-09-2007, 05:27 PM	#7
Mixup Registered User Join Date: Jan 2002 Location: Henderson, NV Posts: 358	Re: TH350 to 700R4 Driveshaft Mine has the 2 bolts that hold the mount to the trans and 2 bolts from the crossmember to the mount. You might have to get a different mount. __________________ 1980 Chevy Shortbed Pickup 1969 Z28 engine Turbo 350

04-09-2007, 05:45 PM	#8
BACKYARD88 On the fast track to nowhere.. Join Date: May 2006 Location: Splendora, Texas Posts: 5,316	Re: TH350 to 700R4 Driveshaft You should be able to buy the speedo gear from a GM dealer individually. __________________ -Mike Owen- Support the board here! 71 Chevy short fleet build thread Double D Norwood, Houston, Cecilia, Jackson, Monroe and counting



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