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Old 03-24-2003, 05:07 PM
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T-350 slipping... low oil pressure... diagnosis?

Hello all,

First of all let me say I'm new here and it's nice to have found such a big resource for rodders. Over on this side of the pond there's not many places to go for advice so I appreciate it even more.

Now to my problem... we have a TH350 in our car (which weighs 1000kg) behind a mildly tuned 350 ci SBC. I'm sure this is a common combination.

We've been having some serious problems with the trans in the past, and we have had it tested and started stripping it now to try and find the fault.

Rather than posting all the details here, I have made a page for it on my website... hopefully no-one'll mind me posting a link - <a href="http://www.funkster.org/" target="_blank">http://www.funkster.org/</a> - click on Cars on the left, then on 'Gearbox' under the Morris 8 section.

I would really appreciate any thoughts from the experts as to what our problem might be. If you need more info, just let me know and I'll provide it as best I can.

Thank you in advance!
--
Funkster

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Old 03-24-2003, 06:07 PM
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your pressures are falling off too much when hot.

Even though the stator support looks fine, they are usually pushed "out' away in the center area from the pump gears from the constant pressure and heat.

We use special fixtures on a basic manual tranny flywheel grinder to flatten out all of our stator supports. Some folks call the stator support a pump cover.

Next you need to check the depth of the pump gears in the pump housing. .002 is really the desired spec.

Flat sand the gears and pump on something large enough to sand the pump. We use 100 grit with solvent to cut then 400 grit to smooth out.

On the clearance deal....I hate to see the thick selectives on the stator area. there are shims for the very rear torrington bearing on the output shaft/ring gear to move the output shaft up some.

The rear shims start at .030 to .045 I think.

If the outer gear has worn a notch into the side of the pump, you will need to replace the pump and gears.

[ March 24, 2003: Message edited by: Crosley ]</p>
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Old 03-25-2003, 03:48 AM
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Hey, thanks for your comments.

I've just measured the clearances on the pump and stator components... the stator is only 'dished' by about 1.5 thou, is this acceptable? It isn't any deeper where the scoring is, and it's very uniform over the surface.

The gears are a bit more complicated, so I've drawn a diagram of what clearances are where, and it's now at the bottom of the page mentioned above.

Do you think that this pump wear is sufficient to explain the pressure drop-off, or should we be looking for something elsewhere in the 'box?

Thanks again,
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Old 03-25-2003, 07:32 AM
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By the way, that's not just a thick selective thrust washer on the stator... it's the thickest selective PLUS a 1/8" thick home-made aluminium spacer 'twixt thrust washer and stator.

If end play is this much, does it mean there's something wrong with the case?

Cheers,
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Old 03-25-2003, 12:02 PM
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Hi there funkster. Good to have another Brit on board. You'll feel at home here!!
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Old 03-25-2003, 05:34 PM
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The case may be a problem or not.

several things can cause too much clearance. mis-match of parts, worn thrust washers, worn thrust surfaces.

At the center support race there is a washer on top of the inner race. You can stack two washers there to tighten things up.
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Old 03-26-2003, 03:50 PM
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Thanks for the advice, I'll shim up the rest of the box if needed.

I should have mentioned before, I took measurements of some more pump clearances... the inner-gear-OD-to-crescent is 20 thou (book says 5 max) and the outer-gear-OD-to-housing-ID is 10 thou (book says 5 here also).

I guess the answer I'm looking for is: Is this much pump wear capable of producing the symptoms we see when the oil is hot?

Tomorrow I'm going to pick up a new pump and housing, and then I'll put the 'box back together and pressure-test everything. Hopefully this will yield some conclusive results!

Thanks for any additional advice anyone might have.
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Funkster

P.S. Thanks for the welcome Deuce UK :o)
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Old 03-26-2003, 05:37 PM
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Will a worn out pump cause pressure loss with hot oil?

I think the question answers it's self.

A worn pump will also allow quicker drain back from the converter
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Old 03-27-2003, 07:20 AM
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Hey, yes you're quite right, 'twas a bit of a daft question.

Anyway, I have been in the garage today to do some pressure tests. I don't have the plate to enable me to check the direct/forward/intermediate clutches from the pan area, so I pulled the clutches out of the 'box and built up the stack on the bench and put the stator in the top. I couldn't get the direct clutch to apply with 35psi air at first, which is obviously a big fault. And then...

... I removed the big extra shim washer, put the stator back in, put some air on it, and it applied straight away! So, everyone's advice seems to be right, shim up the box elsewhere rather than using big shims on the stator.

Thanks for your help Crosley, it's been good to have another opinion on all of this.

Off to buy shims,
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Funkster
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Old 03-27-2003, 08:23 AM
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Argh, where can I get shims? I don't mind mail ordering from the USA, but I can't find anyone who lists shims as being available. Everyone sells full rebuild kits of course, but I don't need clutches etc.

Cheers,
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Old 03-27-2003, 12:28 PM
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Dag nammit... scratch that earlier comment, it seems that the bad pressure test was simply a fluke, when I put the big washer back in the piston applied fine.

Ah well, I guess I'll just replace the pump and put it back in the car. And hope it doesn't melt :o )

--
Funkster
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