Transmission swap- TH350 to 700R4

[snipescastle2]

I'm sure someone has already mentioned it, but if not, the T.V. (Throttle valve) cable needs the correct geometry to apply the correct pump pressure. If you are running a Holley carb like I am, you need the correct bracket that attaches to the throttle arm of the Carb. Not to mention, buying an adjustable TV cable makes setting the proper line pressure easy. You can purchase most everything through Summit/Jets or through Bow tie overdrives. If you don't have the proper tv pressure before driving, you can burn the Trans up before going anywhere.
Just wanted to make everyone aware of this.
Ben

[beanious]

Yep, TV is totally different from kickdown. Got it covered, always good to help future swappers.

Different types of TV brackets below.

[beanious]

Hello everyone, I just wanted to check in and give an update as to how things are going with the 700R4 and share my experiences. So far it has been working pretty well, it shifts when a 700R4 econobox should and the fourth gear with torque converter lockup is a amazing. I’m running 2,000 RPMs on the freeway at 65 MPH. That’s pretty much exactly what I was looking for. There are little details that I’d like to change and as they come up I’ll make sure to document them for the group.

Some things I’ve learned so far:

Transmission fluid has a notable pressure drop when going from ambient to warmed up temperature. Cold temp was 80 F and warm temp was 170F, pressures varied by nearly 80 PSI in park. You might be thinking that is not a big deal but this is the same pressure that keeps the clutches engaged. Long story short, make sure to check and adjust pressures while at operating temperature.

The TCI constant pressure valve body kit applies pressure constantly but not at a constant pressure. You’re thinking, what? … So, it holds a baseline pressure, but of course increases the pressure as you apply additional throttle.

It is highly recommended to get an ADJUSTABLE torque converter lockup vacuum switch; otherwise you could drop out of lockup way early or way late… Trust me; you will want to be able to adjust this to your driving style and preferences.

I have been taking temperature readings over several testing sessions and have consistently recorded the results below for the listed transmission coolers below. Please note these were taken at ambient temperatures of 70 Deg and at 35 mph or lower speeds while driving around town. With colder temperatures and higher speeds the heat dissipation would be greater, but hey you can’t control the weather.

Derale DER-13267
26” aluminum extruded dual pass fin cooler:
5-10 Degrees temperature decrease

Derale DER-15800
Oil Cooler with fan, 11.5 in. x 15.75 in. x 5 in
25-30 Degrees temperature decrease

[bandit0067]

What's the name of this vac switch and where from, I need one......

[Bigdav160]

Transmission fluid has a notable pressure drop when going from ambient to warmed up temperature. Cold temp was 80 F and warm temp was 170F, pressures varied by nearly 80 PSI in park.

Something is not right and it's not about the fluid.

[beanious]

You make it hard to want to contribute to the forum. My pressures are in the correct ranges when warm but when cold they are higher due to the fluid being thicker. Killing me smalls...

[beanious]

Please see below for a link to the part, works great so far and seems to be a well built!

https://m.summitracing.com/parts/tci-cmp3766b

[bandit0067]

Thanks bean, got one on the way..

[beanious]

Also, another bit of info on 700R4 gear shifting. I picked up a table on part throttle shifting speeds, of course it varies per vehicle; weight, governor setup, axle ratios, tires, etc.

The interesting thing to note is that it notes only WOT shifts are controlled by the governor, otherwise it is controlled by the TV cable. I'm going to call into B&M about their governor calibration kit to verify that it only impacts the WOT shifting.

1st - 2nd -15 MPH
2nd - 3rd 25-30 MPH
3rd - 4th (OD) 45 MPH
These are approximate factory shift points.
WOT shifts are controlled by the governor.

[beanious]

Ok, so after some research and calling in to tech support the governor affects both part throttle shifts and wide open throttle shifts. Apparently with the governor tune kit weights change the WOT shifting and the springs more adjust the part throttle shifting.

[beanious]

Hello all! So, tonight I opened the transmission again. There were some afterthought upgrades and tuning adjustments I wanted to make. I changed the metal ball bearings for torlon, removed the stock accumulators in favor for sonnax pinless and installed an internal transmission temp gauge. When I originally put it together, I though I would want a firmer shift but it proved to be too harsh for me. So I went back to the stock accumulator springs, top and bottom. Another thing I did was install the shim in the boost valve that came with the kit. Originally I installed the spring and placed it between the spring and pressure relief valve as in the instruction pictures. This gave me too high of peak pressures. This time I put the shim between the Boost valve and the spring. So far it looks like it is right in range with where it should be. It seems to only affect the high pressures and not the low. I need to do more warm tests though and I'll post the results.

[beanious]

So, another thing that I can pass on. I've logged the temperatures experienced, corresponding to what gears I'm in. I can see why people blow their transmissions by running 4th without overdrive. If you were to mash without OD, you could easily run into a overheat situation and grenade the internals.

Transmission in 4th-Overdrive @2000 RPM
Trans Pan at 140 Deg F.

Transmission in 3RD @2000 RPM
Trans Pan at 155 Deg F.

Transmission in 4th @2000 RPM
Trans Pan at 170 Deg F.

This was all on a 70 Degree day, consistent temperatures and warmed up. Also I do have an external cooler for additional cooling, hooked up right and flowing in the right direction. Yes, the TV cable is set correctly.

[beanious]

Happy Halloween all, I just wanted to give everyone an update with my transmission and how it's been going. I'm going to try to document what I have learned and experienced in order to help out others who may want to use a governor calibration kit in the future.

After finishing up the transmission install I noticed that the shift points were pretty low and it wasn't the best for performance. I know the stock 700R4 is a fuel economy transmission, but it was killing me. The way I see it these trucks get bad gas mileage anyway, if you want a prius, get a prius. I'm sure that my combo didn't help the low speed shifts either.

SBC 350, 700R4, 1800 stall, 4.11 gears, 35" tires.

I bought a Corvette governor to use as a spare and a governor calibration kit (B&M PN. 20248). The corvette governor was just in case there was an issue with my stock governor, there wasn't in the end but I stuck with the corvette governor since it was new.

Transmission shift points are the results of several factors, engine hp-tq, torque converter stall, differential ratios, tire size and of course governor weights and springs. The more similar the easier it is to duplicate my results with the same weights and springs.

As far as shift points are concerned there are cruise shift and WOT shift points, both are adjustable with the kit. The kit allows you to change the shift points, but it is a global change meaning when you make a change it effects shift points for all gears. In order to change a single gear shift point the springs in the valve body have to be changed. These single gear springs are not included in the kit.

My goal was to get it so that it was comfortable for driving on the street. Since I'm not ever going to be racing the truck I was primarily concerned with the cruise shift points. That had the greatest effect for drivability, plus one of the benefits of a 700R4 is that with the TV cable it varies the shift points. If you want to shift a little earlier at the moment, just let off the gas for a second and it will immediately shift.

Some things I've learned are:
You want to match up the heavy weights and strong springs, light weights and soft springs.
Adjusting the inner weights will change both the WOT shift points and the cruise points, but the springs will only change the cruise shift points.
The transmission cover will take 30-60 min to remove the first time, clean out the RTV and any mess. Replace the round gasket on the cover and install the clip. The clip is important because without RTV and the frequent removal-installation it can leak or even worse the cap pop off.
After a few adjustments I got the removal, modification and installation time down to 15 minutes.
Trucks are much easier to make the adjustments to, as I could just crawl under instead of having to lift the vehicle.
Let the transmission cool down after a drive, the fluid can be extremely hot (200 deg. F+), getting burned sucks.
If you run the vehicle for 15 seconds and shutfown the torque converter will fill up from the pan resulting in very little fluid being lost when the cap is removed.

So below are the specs on the changes I made and the results I encountered. I weighed all the parts with a postal scale in be as accurate as possible. I ended up making 6 changes until I found an adjustment I liked.
With shift points it's more of a personal preference thing than anything else, see below for the results.

Stock 700R4 Governor:
Outer weights: 40G ea.
Heavier inner weight: 15G
Lighter inner weight: 15G
Heavier spring: Grey (stock)
Lighter spring: White (stock)
Cruise 1-2: 13 MPH
Cruise 2-3: 17 MPH
Cruise 3-4: 34 MPH

Corvette 700R4 Governor 1:
Outer weights: 40G ea.
Heavier inner weight: 11G
Lighter inner weight: 11G
Heavier spring: Grey (stock)
Lighter spring: White (stock)
Cruise 1-2: 14 MPH
Cruise 2-3: 22 MPH
Cruise 3-4: 44 MPH

Corvette 700R4 Governor 2:
Outer weights: 40G ea.
Heavier inner weight: 10.5G #3
Lighter inner weight: 7G #4
Heavier spring: Grey (stock)
Lighter spring: White (stock)
Cruise 1-2: 15 MPH
Cruise 2-3: 27 MPH
Cruise 3-4: 70 MPH

Corvette 700R4 Governor 3:
Outer weights: 40G ea.
Heavier inner weight: 11G Stock
Lighter inner weight: 7G #4
Heavier spring: Blue
Lighter spring: Orange
Cruise 1-2: 13 MPH
Cruise 2-3: 33 MPH
Cruise 3-4: 65 MPH

Corvette 700R4 Governor 4:
Outer weights: 40G ea.
Heavier inner weight: 11G Stock
Lighter inner weight: 10.5 G #3
Heavier spring: Blue
Lighter spring: Orange
Cruise 1-2: 14 MPH
Cruise 2-3: 33 MPH
Cruise 3-4: 60 MPH

Corvette 700R4 Governor 5:
Outer weights: 40G ea.
Heavier inner weight: 13.5G #2
Lighter inner weight: 11G Stock
Heavier spring: Blue
Lighter spring: Orange
Cruise 1-2: 13 MPH
Cruise 2-3: 28 MPH
Cruise 3-4: 56 MPH

[Jcfcamaro]

Did the transmission bolt right up to your stock 205 transfer case or did the output shaft in the transmission have to be changed?

[beanious]

JFCamaro, when I had the transmission rebuilt I put an Advanced Adapters short outpout shaft in it. There is also the 2" spacer option, but I wanted to keep the combined length as short as possible.

[jocko]

Originally Posted by beanious

So, one of my favorite replacement parts I got for the transmission is the TCI-376020 Constant Pressure Valve Body.

Originally Posted by 67 chevelle

Im not completely happy with my constant presure valve body from tci , it does work well , BUTTTTT , it clunks downshifting from second to first

Wondering if you've experienced the clunk yet bean - also wanted to ask you both which set-up you chose for the cp valve body (I may have missed it buried in the thread somewhere, but couldn't find it): HP, Street, or Street Plus?

[67 chevelle]

When I purchased mine , 2015 , there was only one choice , call and talk to TCI , they said it might get better if I switched to a stock servo , instead of the corvete servo , they are well aware of the "issue".

If they have changed to 3 designs now it may be because of this very issue

[Jcfcamaro]

Ok, Thanks. I'm debating on trying to install a 396 with the 700r4. I know the engine mounts need moved forward around 1 7/8 to keep the shifter for the transfer case to stay in the stock location , drive shafts also. This might work perfect for my build because the 396 needs moved forward because of valve cover and HEI clearance issues against the fire wall.

[beanious]

Yeah, I was surprised it moved it as little as it did. If you use the spacer you can get up to 4" + or -. I haven't experienced a clunk yet but I set the cp valve body to the lowest level and the truck is loud anyway. Keep in mind the general consensus is to not use big blocks with these transmissions in stock form as they are not rated for them. In the back of my head I wonder why I didn't consider a 4L80-E.

[Jcfcamaro]

What would it take to get a 4l80e in the truck. Whould it work with the 205 transfer case ?

[Boog]

Or one up the 80 to the 85? I hear it will handle big blocks just fine in stock configuration.

[beanious]

This guy has a lot of good info on the 4L80E NP205 combo.

http://67-72chevytrucks.com/vboard/s...d.php?t=537481

[jocko]

Originally Posted by 67 chevelle

When I purchased mine , 2015 , there was only one choice , call and talk to TCI , they said it might get better if I switched to a stock servo , instead of the corvete servo , they are well aware of the "issue".

If they have changed to 3 designs now it may be because of this very issue

thank you!