700r4 Gurus

[raymar58409]

Ok guys , what are the weak parts of a 1985 700R4 Trans?
Thanks
Ray

 

[valvefloat]

I know the 2-4 band is week, the TB boost valve is undersized, the 2-4 servo is lacking in clamp load on the 2-4 band, the 4th gear clutch pack is weak. There is limited fluid flow and to few discs. The fact that your TV cable needs to be set just right is bad point to. There are plenty of after market carb brackets and documents to properly mount the cable to your carb. This setting controls fluid pressure. Set wrong and the trans burns up. There are after market vavlebodies that can maintain proper pressure despite improper cable setting. If you buy a Transgo shift kit, They include a set of springs to change. This set increase the pressure on the 1-2 and 2-3 clutch packs. Its a bonus option not required. There is a down side to the 85 trans. No auxillary valve body. The 89s had it. It enables, with the aid of a reprgramming kit, full throttle kick downs from 2 to 1.

 

[Bungy]

It all depends on how much horsepower and torque are going in front of it. If you only have 200 horse going into it, it doesn't have any weak points. But i'm sure you are going to be stuffing in more then that. As well as the items listed above, another weak link is the sun gear shell. Personally I wouldn't waste my time with an 85. Your best bet would be to find an 87-92. After 87 they have all kinds of good updates and are a very good foundation for a strong trans when equiped with the right parts.
I can't stress enough the importance of installing the TV cable 100% correct. I wasted two trannys before getting it right. Bow-Tie overdrives can fix you up in this department. www.700r4.com
Another place for good rebuild parts is www.bulkpart.com
One more thing. Stay away from the Kevlar band. The Kevlar lining will flake off, go through your trans and ruin it. Just go with an extra wide HP band.

 

[valvefloat]

I would agree with Bungy about the horsepower and the sungearshell. Howerever I would negate the 87-88 trans. Go with 89-92. The key is the auxillary valve body. It did not exist until 89. I also believe the spline output was changed but i'm not sure what year was the change point. 89-92 would safe. I would read the article on the chevy hiperformance site called "700r4 deluxe". Theres some valuable facts there. hard hitin and shiftin is also a valuable article.

http://www.chevyhiperformance.com/t...performance_700_r4_automatic_build/index.html

http://www.chevyhiperformance.com/techarticles/65138_adjusting_tv_cable/index.html

http://www.chevyhiperformance.com/techarticles/46140_chevrolet_transmission_swap_guide/index.html

 

[oldimpala]

I would agree with Bungy about the horsepower and the sungearshell. Howerever I would negate the 87-88 trans. Go with 89-92. The key is the auxillary valve body. It did not exist until 89. I also believe the spline output was changed but i'm not sure what year was the change point. 89-92 would safe. I would read the article on the chevy hiperformance site called "700r4 deluxe". Theres some valuable facts there. hard hitin and shiftin is also a valuable article.

I'm actually pretty sure it showed up in 87 1/2.... I've been running a 700R in my car for about 7 years now; starting with a unit from Fairbanks and Level 10. I was happy with it, but being kinda a "New" technology then, it wasn't quite sorted out, and I didn't have it dialed in by pressure, merely feel. Also some issues with the mechanical Converter lockup I got from Fairbanks; it always seemed unlocked when I wanted it locked, and vice versa... Then, I started to tear the input shaft off the sun-shell; Game over.

I bought a Stage 3 Bowtie Overdrives unit; and have to tell you I'm impressed. It's firm when you're in it, and actually mildy pleasant around town. Built like a tank, and customer service is great; I actually like that they won't warrant your tranny until you give them pressure readings; they then walk you through how to correct anything if it's wrong.

Get the better Servo, get the better sunshell, get the upgraded band, Reverse clutch pack (don't know if that was mentioned; another weakness). Basically, buy either a Stage 2 or 3, or equivalent, you won't be sorry. Keep the lockup (Always keep the lockup), and go with a Painless Wiring vacuum/brakelight switch unit.

Oh, and even though this isn't a major concern (Though it's kinda nice), I get almost 15MPG with a Dual-Quad 409, and 4.11's in OD.....

Just my experiences...

-Andy

PS: The wicked first gear makes for some amazingly scary stoplight-stoplight launches, too. Saw a guy in a Z06 turn about 46 shades of white when I launched. We won't talk about what happened when we both hit about 15, tho..

 

[raymar58409]

Thanks guys for the info, definitely helps. I bought this 85 on the premise it was a '92 on the word of an "friend" as I was out of town and left the money with him to pay the guy who he said was honest yadayadayada........ anyhow its mine and I didnt check it out for a year later. No more than 400 hp to go through it. Maybe I'll look for a newer one or an aftermarket one already done. By the way TCI has a continuous pressure valve body that you only use the TV cable to set the shift points.

Thanks Again,
Always count on this site
Ray

 

[valvefloat]

I have an 85 style trans. Its in my 58 bel. I put an 89-92 style trans with the auxillary valvebody in it in my 85 ss. I put a transgo shift kit in it to beef it up. Its one diehard kit. The one thing that i dislike about the 85 is the fact that when you are in 2nd and nail the gas, it will kick down to first. It does kick down from 3-4 and 3-2. I spoke with TCI, B&M, Art Carr, and Transgo. The all agreed that only the trans with the auxillary valve body has enough options to allow a reprogramming shift kit to change this. The is the 89-92 trans. I don't believe the 87-88 trans has the auxillary valve body. That is why it is less desirable. Having said this, I put one in my bel. I don't really hotrod this car like my SS. It works fine for the kind of driving i do with my Bel. I would recommend the Transgo shift kit. In addtion I would get the biggest tv valve available. If you have the dough. The TCI vavlebody is a good way to go. I would also get the Corvette governor. It will allow 5000rpm full throttle shifts. I have the GM part number somewhere. I also have an online source that is much cheaper.

 

[Bungy]

Is it possible that some 87-88s had the auxillary valve body and some didn't? I thought they all did. I know for sure one did as the one in my Chevelle is dated late 86 (for 87 model year) and it has the aux valve body.

 

[valvefloat]

I reviewed an article for Hemmings Rods & Customs October 2000 issue. It specifies that 87 is the first year with all the upgrades so you should be good to go. The articl specifically points out the better oil pump, improved planetary, the larger sprag, and the change from 27 to 30 tooth out put spline.