With the dry roads I had the vette out for 5 days. On the fifth day I got two soft 1-2 shifts and noticed that it seemed to be revving higher than normal to run 75 mph. Three miles later I heard a small soft snap sound and then nothing engine would freely rev as if in neutral. I had it towed to Affordable transmission here in Anchorage, the built the 700r4 the second time. They tore it down and found that the impeller in the pump had broke in 6 or so places. They stood behind there work fixed it free of charge. So anybody have any clue as to what would cause this?

 

Usually, a broken pump indicates a misalignment between the bell housing and the engine. It causes the torque converter hub to put stress on the pump gears.

 

Yep, this is correct

 

Ok so what can i do ensure this doesnt happen again? Another friend that has a shop thinks that at some point the converter might have been slide off the pump lugs and rotated accidentally and upon tightning the bell housing down put undo stress on rg pump before it was realized and caught. Any merit to this thought?

 

They are also using a very early pump. You should have a 10 vane pump no less .

 

Mr. Diehard, can you elaborate some more, could you tell by the photo what vain pump I had, what vaine are there, can you fit a 10 vain or better pump in any 700r4 housings?

 

You can't use stock crap in a HP setup..

#5X. 700R4 Pump with .500 valve & 13 vanes, fits 87 to 93 AVB 700R4 transmissions $195.00

http://www.transmissioncenter.org/700r4_Parts_List.htm

 

So by looking at my picture mine was an 8 vain?

 

That was a very common break point in the early 700-R4 transmissions. I've seen them break with less than 5k miles on full size cars that were not driven hard at all. Granny's grocery getter.
Part of the problem is the pressure regulator springs were on the soft side and allowed the whole assembly to vibrate- that's what shatters the pump. If engine to trans alignment was the problem then there was a very large number of cars and trucks built that somehow got it right- I personally put over 200k on a 350 with a 700-R4 trans and never had any problem with the trans. And also if the alignment was off it would have to leak badly as soon as the pump bushing would wear on the side that was loaded.

GM fixed that problem with a 10 vane pump starting in 1988. The 10 and 13 vane pump parts were available from aftermarket parts guys before that. 10 vane pump with harder than stock rings and no more problems.

 

13 vain is over kill and it is used in the up to 850 hp 700R4s. I also used 1/2 inch steel braided lines to my big cooler. The 10 vain would be okay.

back in the 80's when the rage was to put in a OD tranny I went through 2 TCI or B&M hopped up 700's behind my little 355 ci. Both within days of installing them. I was so depressed I just called up Art Carr (TM) because it was a local company and bought their 850 hp model with a 9.5 3500 stall and never had another tranny problem.

 

The vanes are the workers in the pump , they are not even present in your photo but the pump rotor is and that is how i know you do not have a 10 vane pump.

http://www.ebay.com/itm/2004R-700R4-4L60E-4L65E-13-Vane-Transmission-Pump-Slide-Rotor-Vane-Kit-/171190124334?_trksid=p2054897.l4275
I would not hesitate to use 13. Usually though Transmission shops locally will have at least the 10 vane ...

 

Thanks for all the info.

 

I buy my 700R4 parts from PTAC, also. Iexplained the low pressure readings to them......They advised me to buy a $30 valve body internal spring from them which "saved" me fro having to rebuild my SBC '34 truck with 200,000 mile on the A/T. The 300PSI dash gauge that I installed to monitor the shifting pressures (which now are all witin specified ranges since the new spring was installed) works perfectly. They also advised to make sure that I have a $60 electric/vacuum shift kit installed/adjusted/operating properly to keep from destroying the A/T under heavy acceleration! I will go with their H.D. rebuild kit this fall because they have been so helpful. (Another little-known 700R4 tip is to "allow" the 700R4 to shift into "lock-up" above 90MPH by "slightly-easing-off the throttle to allow the "upshift"/then ease back on the throttle fully.....the car will then be able to reach max MPH (which WILL NOT HAPPEN if the transmission is not allowed to "lock-up" as designed----causing it to XXXXXXXXXXXXXX-plode)

The previous owner just had the TH400 rebuilt on my project '68 Vette....I will install a hidden A/T pressure gauge to monitor the shifting pressures as well (and convert it to "Lock-up", if it is not already converted).

(Being in the aviation field, I rely heavily on gauges to monitor everything)