Mark71

Since I had to re-locate my transmission cooler lines for my headers, I thought about adding a transmission fluid cooler in addition to the stock one. I am not sure on my trans temps right now, but I want to do what I can to keep my trans in good shape.

Can I "over cool" my transmission? I mean, it should stay cool in the summer but not be too cold in the winter. I was going to install the cooler in addition to the stock one in the radiator...

I've heard that some transmissions have an internal "bypass" which prevents oil from going to the cooler when it is below a certain temp. Does the TH-350 have any such thermostat or other provision?

Thanks!

rustyroger

I have asked this question earlier, I was told that overcooling is not a problem except under extreme (arctic) conditions.
I don't think any automatic transmission has an internal thermostat, however there is no reason other than the work involved and cost to stop you fitting a thermostatic bypass into an external cooling system.
Engine oil coolers in rally cars have such a system, maybe you could adapt one to fit, the flow rates would be similar.

Roger.

507OLDS

You can run both coolers with no issues.Run from the trans to the radiator cooler,then to the external cooler,then back to the trans.
However,do NOT install one of those external filters,which uses an oil filter style filter.It sounds like a great idea,but those oil filters do NOT flow enough fluid to keep up with the demand of the trans,and you will starve the trans.The pump in the transmission flows a lot more volume compared to an engine oil pump.I did a test like this in the late 90's,by flowing each cooler,the lines,& the filter,and when it came to the filter,it built pressure,and restricted flow.Just use the normal trans pan filter,and you can run both coolers.

rustyroger

I fit trans coolers to every automatic I buy (unless a PO already did).
The fitting instructions invariably recommend running the line from the trans to the cooler first and then back via the radiator cooler.

I have noticed some of my cars have upshifted a little slowly until the transmission has warmed up a bit, maybe 2-3 miles. I guess they warm up fairly quickly because of all the moving internal parts, fitting coolers didn't extend this to any noticable extent.

You say you have fitted headers, I'm guessing you want to use the performance potential of your car in which case I think a cooler is a wise investment.

Roger.

507OLDS

In my opinion,the fluid in the radiator cooler will be warmer,with it next to the radiator itself,but the external cooler,mounted in front of the radiator,for air to pass through,will have a lower fluid temp,and therefore that is why I have plumbed my lines in the order of trans,rad cooler,trans cooler,back to trans.

Mark71

Hey Rusty and 507 - I really, really appreciate the info.

I don't plan on driving the Cutlass into any arctic conditions (Delaware doesn't get much below 0*F even on the worst days of winter). In the winter mine spends most of its time in my "semi-heated" garage, anyway.

The one I was looking at is relatively small and doesn't have too much surface area, so hopefully it won't over cool the trans oil no matter how cold it gets around here.

The instructions from the one I was looking at advise that either way (trans to radiator cooler to external cooler to trans OR trans to external cooler to radiator cooler to trans) would be possible.

Honestly, I really like the sound of headers and replacing my manifolds would have cost as much (and possibly more) than just putting in headers. I don't expect to turn my car into a race car, but a few extra ponies never hurt anyone.

Glad you mentioned this. I thought that might be a good idea at some point in the future. I'll be staying away from them now...

rustyroger

Seems there are two camps on views on routing trans coolers (three if you count bypassing the radiator altogether).

We could make sound arguments on the relative merits of all three views, whichever way you go if the transmission stays cool and the coolant doesn't overheat you haven't done it wrong.

Maybe a bypass filter which doesn't obsruct flow has its merits, but if you look after your transmissions maintenance it seems like overkill to me.


Roger.