trans conversion question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

meathead95 · 05-17-2005, 02:21 PM

i am getting ready to go to an auto in my 2wd blazer my question is is the 700r4 really woth it as i figure with the 3.07 rearend i currently have with a th350 my final gear will be 3.07 and with a 700r4 i would have to chenge to a 3.73 rear but i would end up with a final drive gear of 2.83 so do you guys actuall think the difference between final drive gears (.24) is worth the extra money for the trans and to change the rear?

also the 700r4 i have has an electric speedo. do you know what or have the parts i need to go to a mechanicle speedo?

chickenwing · 05-17-2005, 02:45 PM

If you are looking at mpg only I'd say no. If you are hauling/towing the 3:73's would make it worth it.

Guff · 05-17-2005, 02:46 PM

I don't know if it would be worth it or not but I just did a 700r4 swap in my truck with 3.73 gears so I can give you the parts you need to change the speedo over...

Drive and Driven Speedometer Gears
Drive Gear Clip
Driven Gear Housing (different part# depending on which Driven Gear you have)
Driven Gear & Driven Gear Housing Seals (these do not come with the housing)

TCI has some good info at http://www.tciauto.com/components/speedometer_gears.htm

I used the plastic Driven Gear Housing from TCI, but I would recommend getting the metal GM housing instead. The plastic housing was very hard to install and even harder to remove. I will have to break it to remove it.

meathead95 · 05-17-2005, 04:50 PM

what did all that cost you? I just called tci and they said they have a kit to swap it over to a mechanical speedometer for 399$ (ouch) I am not paying that lol...... anyone done it cheaper.

**pjmoreland** · 05-17-2005, 06:12 PM

I had a TH350 with 3.07 gears in my truck a few years ago. It was nice and smooth on the highway, but was pretty sluggish starting out from a stand-still. I then switched to 3.73 gears which was waaaaay beetter for starting out from a stand-still, but was not very good for highway driving. I now have a 700R4 with 3.73 gears, and I'm EXTREMELY happy with it. It's got a super low first gear which is a lot of fun, and it's super smooth on the highway.

72MARIO · 05-17-2005, 07:18 PM

Go with 3:73's you will be happy with the way it drives.

BubbaGreen · 05-17-2005, 10:27 PM

700R4 w/3.73 is awesome...
check out tci website for info on tire size/gear ratio for the correct speedometer gears to get. $399 for a mechanical speedo is WAY too expensive...find an older 700R4 and strip the tail shaft if necessary. Best drive gear to get is 17(red) and then get the correct driven gear for your tire size.
Absoletly make sure you get the TV "pressure cable" set up correctly or you will ruin you new trans in short order. Take a look at www.700R4.com for some excellent info, there prices aren't outragous either. Biggest headache is the drive shaft issue and you will have to get a longer speedo cable and/or find a 1.00:1 90degree adaptor.
If you need more info, PM me, I have done this conversion and have alot of GM part numbers if your interested. I think its well worth the effort. Also, dont forget the 700r4 has a lock-up converter, you may want to think about some kind of manual control over this, again, check out the 700r4.com site.

Guff · 05-17-2005, 10:46 PM

Quote:

Originally Posted by meathead95

what did all that cost you? I just called tci and they said they have a kit to swap it over to a mechanical speedometer for 399$ (ouch) I am not paying that lol...... anyone done it cheaper.

WOW! I bought the housing from TCI and it was about $8. The gears were less than $15 each. Not sure about the seals because my cousin had them laying around his shop. If you go with all GM parts, check out GMPartsDirect.com for good prices, just watch the shipping charges, they can be rather high sometimes. Also, there is a lot good info in the FAQ for the 700r4 converision.

tmcgrawlookalike · 05-17-2005, 10:52 PM

I am not paying that lol...... anyone done it cheaper.[/QUOTE]
i just swapped that set up out the other day.the metal gear for the pick up of the electric speed is a b#$%^&*h,but take your time and you`ll get it off.all i did was set the two trans side by side and swap them out.works great.did this at a salvage yard that let me have the stuff i needed,as long as i put their "core" back together.and they didn`t charge me a thing.good luck

05-17-2005, 02:21 PM	#1
meathead95 computer illiterate Join Date: Jan 2001 Location: Des Moines, IA Posts: 6,440	trans conversion question i am getting ready to go to an auto in my 2wd blazer my question is is the 700r4 really woth it as i figure with the 3.07 rearend i currently have with a th350 my final gear will be 3.07 and with a 700r4 i would have to chenge to a 3.73 rear but i would end up with a final drive gear of 2.83 so do you guys actuall think the difference between final drive gears (.24) is worth the extra money for the trans and to change the rear? also the 700r4 i have has an electric speedo. do you know what or have the parts i need to go to a mechanicle speedo? __________________ 72 2wd blazer 72 swb 4x4

05-17-2005, 02:45 PM	#2
chickenwing Lovin' Life in Miss.! Join Date: Mar 2004 Location: Puckett, Mississippi Posts: 1,937	If you are looking at mpg only I'd say no. If you are hauling/towing the 3:73's would make it worth it. __________________ The truck... you hear that? No really, you did hear that?!!!

05-17-2005, 02:46 PM	#3
Guff Registered User Join Date: Feb 2002 Location: illinois Posts: 78	I don't know if it would be worth it or not but I just did a 700r4 swap in my truck with 3.73 gears so I can give you the parts you need to change the speedo over... Drive and Driven Speedometer Gears Drive Gear Clip Driven Gear Housing (different part# depending on which Driven Gear you have) Driven Gear & Driven Gear Housing Seals (these do not come with the housing) TCI has some good info at http://www.tciauto.com/components/speedometer_gears.htm I used the plastic Driven Gear Housing from TCI, but I would recommend getting the metal GM housing instead. The plastic housing was very hard to install and even harder to remove. I will have to break it to remove it. __________________ -Guff 1969 C10 LWB, 350, 700R4, 3.73 gears Last edited by Guff; 05-17-2005 at 02:48 PM.

05-17-2005, 04:50 PM	#4
meathead95 computer illiterate Join Date: Jan 2001 Location: Des Moines, IA Posts: 6,440	what did all that cost you? I just called tci and they said they have a kit to swap it over to a mechanical speedometer for 399$ (ouch) I am not paying that lol...... anyone done it cheaper. __________________ 72 2wd blazer 72 swb 4x4

05-17-2005, 07:18 PM	#6
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	Go with 3:73's you will be happy with the way it drives. __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

05-17-2005, 06:12 PM	#5
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,010	I had a TH350 with 3.07 gears in my truck a few years ago. It was nice and smooth on the highway, but was pretty sluggish starting out from a stand-still. I then switched to 3.73 gears which was waaaaay beetter for starting out from a stand-still, but was not very good for highway driving. I now have a 700R4 with 3.73 gears, and I'm EXTREMELY happy with it. It's got a super low first gear which is a lot of fun, and it's super smooth on the highway.

05-17-2005, 10:27 PM	#7
BubbaGreen Senior Member Join Date: Mar 2001 Location: Cedar Park, TX Posts: 686	700R4 w/3.73 is awesome... check out tci website for info on tire size/gear ratio for the correct speedometer gears to get. $399 for a mechanical speedo is WAY too expensive...find an older 700R4 and strip the tail shaft if necessary. Best drive gear to get is 17(red) and then get the correct driven gear for your tire size. Absoletly make sure you get the TV "pressure cable" set up correctly or you will ruin you new trans in short order. Take a look at www.700R4.com for some excellent info, there prices aren't outragous either. Biggest headache is the drive shaft issue and you will have to get a longer speedo cable and/or find a 1.00:1 90degree adaptor. If you need more info, PM me, I have done this conversion and have alot of GM part numbers if your interested. I think its well worth the effort. Also, dont forget the 700r4 has a lock-up converter, you may want to think about some kind of manual control over this, again, check out the 700r4.com site. __________________ 71 Chevy C-10 SWB Fleetside RamJet-350/4L60e & Compushift/3.73Posi See it at www.prismnet.com/~grzanich

05-17-2005, 10:52 PM	#9
tmcgrawlookalike Registered User Join Date: Jun 2004 Location: warr acres,oklahoma Posts: 650	I am not paying that lol...... anyone done it cheaper.[/QUOTE] i just swapped that set up out the other day.the metal gear for the pick up of the electric speed is a b#$%^&*h,but take your time and you`ll get it off.all i did was set the two trans side by side and swap them out.works great.did this at a salvage yard that let me have the stuff i needed,as long as i put their "core" back together.and they didn`t charge me a thing.good luck



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