Ingar, Norway

I can buy a 700R from a 1987 Caprice.
I've heard you can tell the year from the first digit of the ID number. Is this correct?
Where there any major updates after 1987?

I would rather prefer to keep the original driveshaft. Is it possible to use the Caprice driveshaft? (Long enough, I measured the Corvette shaft to be 28", or too long so that I can shorten it).
Will the differential yoke be of correct type?
Anyone who knows the dimensions of the diff yoke?

Strike3

I've been watching your inquiry as I am also interested in this conversion.. I'm am a little disapointed that you received no responce, but my own questions are more basic as I am just now becoming aware of the benifits of this conversion. I too have a 1980 L-82. I like the idea of lower 1st and 2nd gears for better low end performance along with the higher final ratio for crusing economy. It sounds like we may be able to gain the benifits associated with changing out the rear differential (for exampte to 3.55 gears) while improving gas millage. I believe the 700R is 3 inches (about 75 millimeters) longer than the TH350, so I'm wondering about drive shaft and mounting change requirements and cost. Locking torque converters were available in 1980 but not on all vetts. Some 1980's have it and some dont. While I'm sure the 700R was computer controled, those 1980 Vettte's with locking torque converter are vacuum controled, but I don't see this as a problem. I share your concern as to weather there is a "best" version or year of the 700R, but I also would like to know if they were equiped with differant gear ratios, either by year or by vehicle make or model. I am pleased to see new products on the market to replace the shift indication on the council so that the position indication matches the patern of the 700R and looks like factory. Come on guys, help us out!!

81vette

Can't help you much on the how-to, but I did see a kit in Eckler's for this conversion. You might want to check the other stores too, like Zips, etc., for the kit and more information. I know there are some on here that are running this set-up, so maybe if you keep this up top they'll see it and respond.

MIKER

In August 2001, I completed the installation of a 700R4 into my ’80 along with a new 383.
Not counting the price of my transmission (purchased used for $350. It failed 1700 miles later on Nov. 7th) here is a list of the things that I did and the parts that I purchased.

I took my used transmission to "Howards Transmissions" in Stephenville TX.
They installed the following
-Filter Kit. $25
-Lock-Up Valve Assembly. $28
-TransGo 3-4 Max Throttle Kit. $64
-Corvette Servo. $23
-Pump O-ring, Gasket, Bushing, and Seal $15
-Labor Charge. $150
They suggested that I go ahead and let the do a complete rebuild while they had the transmission in the shop but said to give it a try and that if it didn't work out, return it and they would rebuild it for $450. Now that the transmission has indeed "failed" I wish that I would have had them complete the job then but I was hoping to save $450 and not have any problems. It was a gamble that has only cost me the time spent on removal and re-installation.

-Dipstick tube and indicator for 700R4 from Bowtie overdrives ~$22.
-Adapter kit for TV cable to stock Rochester carburetor, from Bowtie overdrives ~ $45.
-Changed from electronic speedometer sending unit to a mechanical gear driven unit from Bowtie overdrives ~$45.
-Had the drive shaft shortened and new U-joints installed at
-American Drive Train Repair
2519 N.E. 36th Street
P.O. box 161427
Fort Worth, TX 76161
817-831-7878
Shorten and balance drive shaft. $49.50
((Dynamic balance @ Barney’s discretion. $29.00+ (not required)))
2-U-joints ($13.48 each) $26.96
Labor for replacing U-joints. ($8.75 each) $17.50
Total bill $96.18

-The drive shaft yoke from the TH-350 worked in the 700R4
-Modified stock cross-member. (moved the mounting pad ~2” back and moved emergency brake cable over away from the U-joints.)
-Modified the original TH-350 shifter bracket that mounts to the side of the transmission pan. (The distance between the pan bolts on the TH-350 were ~3 ½” apart and the pan bolts on the 700R4 are about 3” apart). We simply cut a 1/2" section out from the middle of the bracket and welded it back together.
-The stock speedometer cable is supposed to be able to reach the extra couple of inches required. I can’t verify this, I had to purchase a new one because my old one was broken. The new one came out about 12” longer than the old one. (almost too long) New lower cable ~$16.
-I will modify the shifter guide plate located in the console below the shift lever to allow placing the shifter into 1st gear. I’ll save this for another time because it is not critical.

I don’t know if the transmission lines from the TH-350 will work or not because mine were so butchered up from previous repairs that I am replacing most of them with new steel lines using compression fittings.
Here are more details regarding the steel lines:
For my 700R4 install I used part of the existing lines and added new sections to complete the job.
I purchased two separate pieces of new steel tubing and 4 brass compression fittings from NAPA auto parts.
From the radiator end: The original connections to the radiator consisted of short pieces of flared tubing (~3"). These short ~3" stubs were connected to the remaining length of the lines that connect to the transmission with short pieces (~3") of high pressure rubber tubing w/hose clamps.

From the transmission end: I used about 12"of the original tubing from the transmission (in and out).
For the new section placed in between the radiator and transmission: Basically I removed and replaced the tubing between the 12" stubs from the transmission and the original lines which were cut near the fuel pump. I used a decent quality tubing bender. It was the first time I had used one and it didn't seem too difficult to use.
The original transmission lines had been routed below the starter which made removal of the starter somewhat difficult. I bent the new steel tubing section along a path that provided clearance for easy starter removal (followed the frame curve to below the A/C evaporator core housing and back out and up to meet the (~12") stubs coming from the transmission.
To sum it up: From the radiator> ~3" metal tubing> ~3" rubber hose> new section> ~12" stubs connected to transmission.

I know a picture would be better but I don't have one of the transmission lines right now so this was the best description that I could give.
All in all, the modifications for the swap weren’t nearly as bad as I thought that it would be. I worried most about the cross-member modifications but a talented friend using a welder, cutting torch and tape measure made short work of it.
I’m just guessing, but if you have all of the parts and access to the tools needed, I think that you could tackle it in one weekend with help from a friend.

As far as transmission selection, I’ve always heard to go with a 1988 or newer model 700R4. The prices can range from as low as ???$ for a used one up to ~$1200+ for a new or rebuilt one.
I'm running a 2200 RPM lock up stall converter. I paid ~$180 for it at the local shop.
Bowtie Overdrives sells a 1800-2200 lock up stall converter for all street applications. These converters feature brazed turbine vanes, Torrington thrust bearing, heavy duty sprag clutch, larger dampening spring assembly, carbon fiber clutch material and is fine line balanced for smooth operation. Price is $154.00

I currently have 3.08’s which are way too tall. I am changing to 3.73s.
I purchased my 3.73 ring and pinion gear from "Tom's Differentials" for $141 at http://tomsdifferentials.com/cat26.htm
I purchased the complete '80-'82 differential rebuild kit from "Bair's Corvettes" for $89 at http://www.bairs.com/page22.asp
Check out Smokemup.com to see what your new speed MPH vs. engine RPM would look likehttp://www.smokemup.com/utilities/calc/mph_range2.cfm
Bowtie Overdrives sells lot's of pieces and parts for the swap too!
http://www.bowtieoverdrives.com/68-81Corvette700R4.htm
Budman78 has provided this link for a business that also sells a modified cross member for the 700R4 swap. "Muscle Members" http://www.x-members.net/

(edit/modification = adding to cut-n-paste list)





[Modified by MIKER, 5:35 AM 11/19/2001]

Ingar, Norway

Thanks for all info!!

I have no bought that 1987 trans. It had mechanical speedometer sender.
It looked very clean inside. An interesting observation was that there is a large magnet glued to the pan.

I can confirm that you can tell the year from the first digit of the number. Also, the "new" units have 732 as the last three digits in the die-cast number on the front (behind the converter)

They couldn't find the Caprice shaft, but I got a Spicer instead. I was also told that I would have to reuse my rear yoke since this is special to the Corvette. Normal yokes don't have fasteners for the U-joint, they are designed to be pulled out with the shaft, which is not possible on the vette.

It appears that nobody in my part of the country can shorten the shaft. Only option is to send it away and pay $300...

Is it possible to do this job myself? I have access to a shop with a big lathe and welding equipment.

I also got a "trough hole" crossmember which I will use for the conversion. (headers and true duals...)


Strike3: To my knowledge all 700 have the same ratios. You can use the same lockup signal as for the TH350. But I guess you get better control from a TPI system.
The lockup socket has 3 prongs. My TPI drawings shows only 2 connections (lockup and return to the brake switch.) What's the last one used for?


I will change filter and seals before the trans is installed.
Any other things do check while I have it out?

Does it exists any books specific to the 700? rebuilding, mods etc?

MIKER

Check out this formula for selecting the correct speedometer drive and driven gears.

chevluvr

I am in the process of making this conversion. Once I finish painting the undercarriage I will be starting my installation. I have a 3.55 rear-end aand I am definitely looking for better performance and gas mileage. Miker did a great job of giving you a lot of information. I will post more information if I come across something new. Xmember( http://www.x-members.net/) is the way to go on the crossmember. I e-mailed him and he said the crossmembers are of the same design. Definitely a much better price. Everything else I purchased from bowtie. Lots of Luck! :cheers: :)

Ingar, Norway

Thanks again!

I've done the calculation, and with my drive gear (18teeth/Blue) the driven gear should be 42 teeth. That's with 3.08 ratio and 255/60.
At present the driven gear is orange (35teeth).
Will I have to replace the drive gear also? How can I find out which drive gears that is compatible to which driven gears?

Ingar, Norway

I'm still trying to find out what that 3rd wire is for.
It goes to a sender (pressure switch or temp sender?) marked number 1.

The other two leads are for the lockup relay in series with another pressure switch, number 2.




[Modified by Ingar, Norway, 6:58 AM 11/22/2001]