700R4 Governor Modification request for info

[Guest Rick Johnson]

Does anyone have experience tuning the shift points on their 700R4 trans. B & M sells a kit of 6 different weights and springs which I purchased. In order to minimize the amount of tuning required to dial in some Hi Po shift points, it would be nice to get a listing of other peoples spring/weight combinations.

Please help if you can.

[Guest Tom Scala]

Rick,I've used the B&M kit and have these observations. Note where your 2-3 shift point occurs now. If you want it to be higher put a lighter weight on just one side of the gov. Check again. Changing only one weight seems to alter both 1-2 & 2-3 shift points the same amount. If it's about where you want it you can start altering the springs. I've found going to a lighter spring on one side(the side that has the lighter weight)will raise 1-2 shift several hundred rpm while the 2-3 is raised only slightly. Try to get both shifts to happen at the same rpm. Then go back and alter the weight again as needed to get the desired shift points. Note that engine torque,vehicle weight and torque convertor stall as well as trans fluid temp will affect shift points. A certain combination on one car will behave differently on another. Make only small changes each time. It's a time consuming process but well worth it especially if you are going to be doing some bracket racing. Note also that some auto transmissions have a rpm limit on how high you can shift,even manually. You can put it in low,floor it and it will shift automatically into 2nd at a factory predetermined point without you moving the lever. A good trans shop will be able to modify the valve body to override this feature and let you alter the automatic shift points to your liking. I hope all this makes some sense and helps you to go in the right direction.

[pparaska]

quote:

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Originally posted by Tom Scala:

...Note also that some auto transmissions have a rpm limit on how high you can shift,even manually. You can put it in low,floor it and it will shift automatically into 2nd at a factory predetermined point without you moving the lever.

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I had a Camaro with a TH400 that had that "feature" I don't know the RPM it happened at (didn't have a tach), but I seem to remember it was 5800rpm or something (per a Chevy manual). Pretty damned hard shift too. It would definitely squack the big tradials I had on the back (327 Chevy with the 327/350 cam). One guy I street raced asked if the car was a 4 speed, after I beat him . I used to blow out the rear u-joint about once a week (bad pinion yoke as well) do to that "feature". I was a young high school kid, and didn't mind spending every Saturday morning replacing a u-joint - neither did my girlfriend. Thanks for the memories - those are twenty years old.

 

Pete

[Guest Rick Johnson]

Thanks for the response. You have basically confirmed my understanding by saying the weights control the overall shift points and the springs determine the separation of the 1-2 Vs 2-3 shift. Please read my summary below and see if you can add too it.

 

It seems the large outer weights swing out at very low RPMs and apply spring force to the small secondary weights. The secondary weights then push on the governor shaft. At very low RPM's the small secondary weights are too light to generate enough centrifugal force to add much to the forces being applied to the governor shaft.

 

As RPM's increase, the small secondary weights begin to generate some small centrifugal force. Additionally the large outer weights probably continue to swing out which further compresses the springs. So at this point the governor is receiving a large spring force and a small secondary weight centrifugal force.

 

Soon afterwards, I suspect the outer large weights bottom out which limits any additional preload into the springs and thus secondary spring force reaches a maximum. Centrifugal force from the small secondary weights continues to rise and probably becomes a significant influence to the overall forces.

 

After this RPM, I suspect the only increasing force on the governor is a result of the smaller secondary weights gaining centrifugal force which increases as a square of velocity.

 

My guess is this high RPM centrifugal force at the secondary springs controls the full throttle 2-3 shift. This is why you say weights are so critical for the 2-3 shift.

 

The biggest question is at what point do these events really occur.

 

Please add to this understanding.

 

[This message has been edited by Rick Johnson (edited March 27, 2001).]

[Modern Motorsports Ltd]

I'd just like to add for others/newbies benefit that IMO a good 700r4 starting point is to start with a corvette governor initially vs. camaro/truck etc, ~$40-50 max and fine starting point that may even be fine as is.

[Guest Tom Scala]

Your explanation seems pretty thourough, I can't really add anything except it's hard to tell exactly what the shift points will be when you make changes. There is no hard and fast rule that says if you go one step lighter on the weight rpm will change X amount. Each application is different. When I changed my 406 for a 469 shift points went up 200-300 rpm. A higher stall convertor added a little more than 100 more. Why? I dunno. More torque run through the trans will raise the shift points though. Thats why I like to make small changes since there is a chance the engine can overev during your "testing". I've found after the car sits for awhile and the trans is cool it will add around 150-200 rpm to the shift points as apposed to one thats been driven for a while and allowed to heat up. Probably because the fluid has thinned out when it's heated and offers less resistance to the weights' action and also the increased torque of the cool motor. Does B&M currently sell that kit? They quit making it a few years back.

[Guest Rick Johnson]

B& M still makes the kit. It is part number 20248.

 

Did you happen to keep notes of which weights and springs you used and your progression of changes? If so it would be a great aid to help estimate the level of change I might expect. (I know it wont be exact but it might save me some time. As you can emagine, access to the governor requires a bit of time. I would be happy to call you if typing it out is a pain)

 

Incidently I started with the corvette governor but WOT shift points were still only 4800 and 4600.

 

I also remember the 1 - 2 shift that would occur even if the lever was held in first gear on the Turbo 400. A buddy of mine from GMI at the time told some of the GM trany gurus that this would happen. At first they did not believe him.

[Guest Tom Scala]

Rick,I probably do have my spring/weight combos written down somewhere. Check back here in the next few days, if I find them I'll post them.

[Guest Rick Johnson]

Thanks Tom,

I plan to make my second governor adjustment try this weekend so I will check back on Friday night.

[Guest Anonymous]

To stretch or change shift points is a fucntion of several things. The T/V cable will change shift points, servo mods will also change shifting charactistics. There are a number combinations that can enhance your 700R4's performance. The governor is one of the players in the equation. Let me know what it is you are trying to do and I will help you get there without spending a ton of money. We build 700's as well as many other types of transmissions for drags, circle tracks and classics. Each trans is built for the specific vehicle.

I have an 83 280zx with a 331 cu in chevy and a 200 4r trans that is quite the performer. I removed the 700 4R due to the deep 1st gear (3.06). The ZX runs much better with the 200r4. With the 700 1st gear was gone so fast and 2nd was such a big jump from 1st that the engine power curve would suffer. With the 200r4 the car launches better and the engine has a smoother transistion from one gear to the next, kinda like a close ratio standard trans.

[Guest Tom Scala]

Rick,This is what I found:

Stock: 1-2 4600 2-3 4800

Replaced 1 stock weight with #3 B&M weight:

1-2 4800 2-3 5200

Stock wt on blue B&M spring #5 wt on yellow:

1-2 5500 2-3 5500

Stock wt on purple spring #4 on yellow:

1-2 6000 2-3 5100

Stock wt on blue spring #4 on orange

1-2 5400 2-3 5200

There were MANY more but this should help.

Don had a good point about the big spread between the 700R4's 1st & 2nd gears. Maybe you could try letting 1st wind out a little more so the rpm's don't drop too far on the torque curve after the shift. Good luck.

[Guest Rick Johnson]

Tom,

Thanks for the weight and spring specs. I will compare them to my notes and use them to help tune my shift points.

 

Don,

Thanks for the offer of help. I totally agree that the 200 would be the optimum trans. The 3.06 is way too much. I did not change to a 200 with my latest project because the rear mounting pad location is about 4 inches rearward of the 700. My 2 1/2 into single 3 1/2 inch system merges right behind the mount to allow room for a Borla Multicore muffler in the tunnel in addition to my Dynomax in the rear. So I am stuck with a 700 but at least my exhaust is quiet.

 

My recent 700 rebuild included 9 friction plates for the 3rd clutch and 6 friction plate forward clutch plates - with the wave washer (both of these clutches were burnt. I already had the larger servo and .50 boost valve.

 

I installed a Gil Younger SK700 shift kit and then modified it based on some "experts opinion" around here. To put it mildly it was all messed up. I bought a new P spacer plate for this 86 model and basically stayed within the kits guidelines except for 2nd apply orifice which I increased to .104 dia. I still feel the minimal throttle shift into 2nd is too long so I was going to up the orifice to .111 dia. I considered shortening the servo travel length but have chicken out for now. What would you do??

 

One other question::

When I go from neutral to any forward gear, the forward clutch bangs really hard and the hotter it gets, the engagement becomes down right obnoxious. The 1986 has no forward accumulator but the schematic shows an orifice. I cant find the orifice. My pump body was changed to a later version and I am thinking the orifice was in the pump of the old models but not in the 87 and up because they got the accumulator. Anyway, I made an aluminum plug which I belt sanded to fit into the case oil passage channel. I then drilled a .070 hole in the plug to restrict flow to the forward clutch. I got a small improvement but not enough. I plan to try a .059 hole this weekend. Do you know where the original orifice was and what size it was???

 

As always, thanks for the time and help.

 

Rick

[Guest Anonymous]

Rick,

Sounds like you have been into this trans quite a few times. Can you tell me what year the front pump, the valve body and the case is. The year is indicated in a cast stamp like circle on each of these components. The date is generally in the very center of the circle and the numbers are very small.

Pre 87 700's are not the best to be building, they have many short comings and modifying them is not as easy as the later 700's. It appears you have a mix of components at present which I would like to better understand. I would not like to send you off on a wild chase with out understanding a little more about the present transmission configuration. I need to fully understand what has been done to this trans no matter how small of a modification was done.

Did you do any modifications to the front drum or the case itself? Did you perform any leak checks to the front drum, especially around the input shaft. What type of seals are you using on the input shafts? What has been done to the valve body.

If you do not mind taking the time we can try to resolve your problems one by one.

Don

[Guest Rick Johnson]

Tom,

Well, this may be long.

1986 700 (bought before I knew better)

1986 Valve Body - separator plate P

? pump body - but according to the ATSG manual it is post 1986 because it has the cast in ledge that prevents the later model pump gaskets with the vent flap from being sucked in and pluging the vent. Interestingly enough, oil leaking out the vent was the original reason I pulled the trans out - I had the non flap gasket and i was dumping fluid under hard braking)Also has 10 vane pump.

1987 and up lo sprag

1987 and up forward sprag

9 plate Alto standard duty 3 clutch pack .030 clearance

6 plate forward clutch with wave plate .040 clearance

standard duty 2-4 band - probably a bit too much clearance - approx .10 stroke clearance

Corvette servo with .100 machined of the apply piston - this may account for the long engagement time into second

.50 boost valve

slightly larger rev valve ?

Gil Younger kit - with hind sight I would not use it again - it has a stiffer 2nd servo spring and a stiffer 2nd accumulator spring

My 3rd feed orifice is .110. (third hits with a bit of a clunk)

My second orifice is .104. (Second apply under light throttle is too slow and long although medium shifts are hard and fast)

 

My complaints are shift points which I think I will be able to tune with some governor mods.

 

Other complaints are long 1-2 band apply under light throttle but as soon as the TV pressure goes up from hitting the gas, the 2 shift becomes very aggressive. I am afraid if I increase the 2nd apply orifice that I may fix the soft/long apply at light throttle but then cause an even more aggressive shift at medium throttle. I considered reducinng the accumulator stroke for shorter light throttle apply times and leave the orifice as it is. What makes more sense to you??

 

The 3rd apply is a bit short and quick. I thought reducing the orifice to about .101 might mellow out the hit without making it too slow - it does have 9 frictions at only .030 clearance.

 

Lastly the darn forward cluth hits like a sledge hammer. I noticed that the oil flow routing changed on the 87 models. It looks like a different passage in the pump is used. But occording to the manual, my 86 does flow through the pump differently. It is too late for me to trace the path through the pump because the trans is in the car, but the part of the case that I can see does not have an orifice in it. I mentioned I installed an .070 orifice in the case just before the oil reaches the pump on its way to the input shaft. I believe a smaller hole (.059)will probably reduce the apply rate some what. Current line pressure at idle is about 70 pounds which looks to be in spec.

 

The only negative I can see to a smaller apply orifice for this static piston application is if there is a bunch of leakage after the orifice that would prevent the forward clutch from receiving full line pressure. The only place for leakage would probably be the white rings on the input shaft. (They were replaced and a new reverse drum was installed so this area should be pretty tight.) It would be nice to know what the stock orifice was to the forward clutch. I have a feeling the Engineers determinned that the only good way to get a soft apply was to add the accumulator that they added for 1987 - but I would like to do the best I can with what I have.

Maybe you could e-mail me with your phone number and I will give you a call.

 

Thanks for considerinng all this info.

[Guest Anonymous]

Rick

As long as your pump is not a mid to late 87 we can go forward. The mid year 87 incorporated an auxiliary valve body at the rear of the trans which was connected by a transfer tube.

There are TV cable adjustments that I assume you have made. I would like to be sure the TV is correctly adjusted, this gives the base line to fine tune the shift points. You did indicate aggressive throttle did change the shift point which is related to the cable.

I will digest what you have in this trans and see if we can come up with an answer.

We do not run the 9 pack in any of the 700/4L60/4L60e's that we build. We found the steels do not dissipate the heat and burn prematurely. We run .050 cls for most of the packs. The other very important check is the pressure check to assure no leakage around the input shaft. We also block the vent hole that GM introduced in 87, these mods really help the forward drum life.

We maintain the local county police car fleet and these mods among others seem to add life to the trans.

I will email you my phone number so we can better understand the problem. Please try the TV cable adjustment, sounds to me as if the cable is to loose.

Don