200-4R Pump priming spring question


May 24, 2001
Question for the experts on pump priming springs:

I measured the stock single spring from a KC model trans and it calculates out at 120 lbs/in and an installed pressure of 39.5 lbs. The Gil Younger No YoYo high rev kit spring calculates out at 193 lbs/in with an installed pressure of 44.5 lbs.

I haven't caluculated a double spring yet. Does anybody know what is optimum spring pressure and rate for the turbo engine? Is there a critical frequency to avoid to ensure pump slide life? (I've broke em before)

I'm not Chris, or Bruce, or Mike K., so I'll just give my $.02:

I'm also interested since those of us with engines that red line below 6,000 rpm are a different world than those with higher rpm limits. Yes, I know about the higher rpms affecting this type of pump. But how much slide spring do we need below 6,000 rpm?

As far as oscillation frequencies of the slide it seems that's why GM went to the double pump slide spring. The 10 vane pump rotor is much better than 7 vanes for flow stability, but 13 doesn't seem to help much. Go with 10 vanes if you have 7 now, but check the clearances.

The stock pump rings are too weak, even for stock use. 200's & 700/4L60's are know to have rings break just driving normally down the road, so use an improved aftermarket type of ring, a MUST. Bruce & some others have billet rotors & slides as well.

It seem you can't just slam this pump together, either. All the pump clearances are very critical:
the main reason for the double pump primary springs is to increase the bias of the slide into the higher output position attained when the slide is pinned against the pump body by the springs.this increases pump volume and the slide is able to stay in high volume position even when fought by decrease oil attempting tocompress the priming springs and decrease the amount of oil volume drawn into the rotor to be compressed and pressurized.also it reduces slide bouncing on shifts and other modes of operation when decrease oil gets runup against the slide when pump output changes.this can cause slide breakage as well as reduce pump output.although not stated in our manual we have certain times when we install a blocker in place of the springs to have a fixed output pump.this is done in combination with bleed holes to reduce spiking and mixing line and decrease oil at the pump body.still studying this mod and it does show promise as well as reduce rotor and slide breakage.the double springs we use are the most efficient when used with our pr system and other calibration mods.

Have you calculated the spring rate and installed pressure for the double springs? The number of springs shouldn't matter...... just the installed pressure and spring rate. That's what you're really after, right?

Have you thought about limiting the slide travel instead of fixing it at max output? A spring installed very close to coil bind would still allow partial travel to smooth out pressure spikes, but would not allow full travel to the minimum output position.


I'm with you on the steel pump rings. I never reuse the stock rings. I have broken a 7 vane slide in the past. Cracked it right at the pivot point. This was on an engine setup that regularly went to 5900 RPM. I was lucky it didn't tear up the pump body or cover when it broke.....just lost it's prime. I replaced the slide and rotor with 10 vane Delco parts and never had another problem.

The pump I am working on is for my street car. It won't see duty beyond 5500 RPM. I'm reusing the 7 vane slide and rotor because they are in perfect condition and fit the pump cavity with the right clearance.
i believe the theory of using two springs is to eliminate the load placed on one tight wound spring by sharing it via two,much like engine valve springs.also it can remove vibrations transferred to the slide during operation.ive never calculated the compressed pressure of the springs but know what has worked for us up until now.i would surmise that the double spring is identical if not stiffer to the transgo assembly.increased pump volume does increase the load on the rotor and slide as well as absorb minute amounts of engine power but it also floods circuits with oil to reduce oil volume loss at apply elements in the form of bleed off and circuit crossleaks inherent in the design of automatic transmissions.initial designs of spring rate must have taken into consideration engine rpm and decrease oil area fed to the slide to move the slide and compress the springs to cause low output mode.when the vehicle is not running the slide is in the hi output position.variable displacement pumps are not as efficient as a similiar volume discharge gear type or geroter but they do have operating principles favorable to the original intended purpose of the original design parameters.
I just recalculated the spring pressure of a double spring setup vs. single stock vs. the No YOYO kit single spring. I came up with the following installed spring pressures at 1.47 installed height (full output slide position):

The previously posted numbers were incorrect.

free length---wire dia.---coils rate---pressure @1.47
Stock single---1.800---0.086---9---194---64.02
Double outer---1.780---0.088---9---231---71.61
Double inner---1.790---0.055---14---80---25.6
No YoYo---1.700---0.094---8---328---75.44

Spring calculator

Chris, If maximum spring pressure is the goal, the double springs have the advantage.


What you said about cracking the pump slide is making me rethink not using a billet slide & rotor! I thought I could get away with reasonable power & rpms without one. Yikes. :eek:
your right on que.why not post a link to pts site for the billet slide and rotor?your a crafty individual at peddling bruces products,perhaps you should get on the payroll :D
Bruce doesn't have a section on the billet slide & rotor on the site. :biggrin:

Plus, I don't know if you have to buy a full pump to get it.

Does anyone else have a billet slide & rotor? :confused:

If I can get a improved part from several sources, I'll shop around. If there's only one source, what am I to say?

And some things are still muddled. Who has the BEST valve body kit for the 200-4R? There must be a dozen different vendors.

And I can find a hardened slide pin from Sonnax, but not the slide or rotor.

Often if someone wants help, I send them the closest shops on the list on this board elsewhere.

I saw a 700 with pump ring failure way back in '83 a friend was working on. Just a stock GMC PU with 50,000 miles. That image has stayed with me, and I still hear the horror stories about pump failure.

And I still see plenty of sentiment on some boards to junk the 200-4R, and install a built 400, that it's not worth the time & money. I think otherwise, no matter who they buy parts from.