Machining the Pump Cover

[KEhrhardt]

This question is for Bruce or Chris. I currently have a '690' pump apart during a rebuild. I pressed in a new pump bushing and modified the pump body by drilling out the drainback holes. The pump body looks good. Now I pressed in the hardened stator into the pump cover and during inspection of the cover there is some scoring that can be felt with the finger nail as it is passed over the surface. I indicated it on the surface plate at work and it is around .001" deep. I am ready to resurface the cover on a lathe to clean it up. My question is regarding the setup of the lathe. Is it the desired procedure to chuck the pump cover in the lathe by the stator tube and then cut the cover face and then the back of the pump cover? I am going to take only the minimum material from the cover to clean it up, but how much material can be removed before the pump cover is no longer usable?

 

[chris718]

no more than .040".there is a passage crossdrilled that will give trouble if any more is taken off.you cant clen it up with a sharpening stone?we chuck them in the lathe with a dummy tube.picking up the center from the stator tube hole.

 

[KEhrhardt]

Thanks Chris, I will try the stone first, then machine if necessary. There is a couple of gouges where perhaps some debris was caught under the pump vanes, or maybe it is a mark made by the pump ring, I don't know. I measured the thickness of pump cover carefully (front to back on machined surfaces using a micrometer) around the outside of the pump cover and it varied by .010" or so side to side. So I was thinking I needed to machine the pump cover anyhow to 'square' it. I think this pump has been messed with before because it has some mods already. A '690' pump body, 10 vane rotor, locktited bushing and seal and it was pulled out of an 85 MCSS (85CQ on the tag). When I got it from the guy at the swap meet he said it was rebuilt some time ago.

 

[KEhrhardt]

Stone didn't work so well. Kissed the front cover .003" on the lathe, cleaned it right up. Cut the back of the pump parallel. Good to go now. Ready for reassembly. :smile:

 

[A. G. Olphart]

Wish that my lathe was that big... bad lathe envy here.

 

[jakeshoe]

A.G.,

Many times I've used a brake lathe to turn down apply pistons for higher clucht count...
You could maybe do this on a front pump...

 

[A. G. Olphart]

Thanks Jake- that's a great application of available tooling... I wouldn't have thought of it, but sure will now. :smile:

 

[WE4]

You need to..

Parrell deck. Meaning, you chuck off the center of the stator tube. Measure the runout. No more than .002 is acceptable. Then you cut the back side of the pump to make true. (None are ever perfectly straight, so you need to true it up or it will sit in the case crooked. Even if it is only 5-10 thousands, at the hub that is a ton.) Then without disturbing the setup, bring your carriage around and surface cut the front. Only cut enough to clean up. And like Chris said, there is a passage in the vent circuit that has to be .040 or more. We mill them if it is less but most don't have the ability to. Also, cavity depth and rotor and slide thickness play a MAJOR part here. Read Strengthening the 2004r on the top of this forum where the pump is explained.
I have been dealing with these pumps for a long time and have them pretty well down. However, I just had one fail the other day with stock rotor and slide in it, all machined perfectly, so, anything can happen. With the billet rotors and slides tho, we haven't had 1 failure.
Bottom line is, the pump MUST be done correctly or the whole trans could go to crap fast!.

Bruce
WE4
www.PTSXTREME.com

 

[chris718]

jake the brake lathe also helps when finishing the outside surface of drums also.

 

[jakeshoe]

Another good application Chris
Gotta love the forums for spreading knowledge.