I have read and read and now have so much info that I don't know wtf.

I read the temp in the test port location (ps - by mlps) will be lower than the leaving-the-trans cooler line temp?!? I have a sender in that hot line half-way to the radiator. Should I move it to the test port? If the cooler plugs/slows will it ever read a high temp where it is now? Two temp guages (one in each loc)?

I have an intermittent prob with spikes of temp in second gear. I hauled trash this weekend - ambient 25*, trailer at 6k, 60mph, tt @ 190*. Then I get to town and turn the corner and when it hits second the needle soars - red light goes on in the tt gauge - WHOA!!!
But.. I plowed snow this a.m. and it hits second lots during the course of the morning and I don't get a spike in temp at all.
I am leaning towards a bad seal internally that is affected by all the heat from normal towing and then it screws up allowing some low pressures and slipping etc.

I am going to do a new filter, drain the tc, Mobil 1 full syn (handles extreme heat better w/o breaking down?), B&M fan cooler w thermo switch, (my 99 didn't come w a rad side cooler?!) and a new bypass tube/valve. Delete the existing puny cooler and flush the lines as much as poss. I know I will be told to re-build, but I just don't have the resources right now and hope this is a band-aid till then.

Any suggestions?
I am hoping Mark K will look at this post.

99 f-250 SD, 5.4, 4wd, 4r100, 4.30 ratio

 

Naw, he'd never look at this!

I think your temp spike is due to the location of your sender. It is normal to have LARGE swings in temperature in the line to the cooler. That's why the fluid is sent to the cooler, because it's HOT!

If the cooler were to get restricted you would see the temps go up. If the cooler is totally blocked the sender in the cooler line will never see hot fluid.

I believe the test port is a MUCH better place to read the transmission temperature. It will show the average temperature of the transmission, which I find a lot more useful than watching the huge swings in temperature of the fluid going to the cooler. I don't see a need for a sender in both places.

 

Thanks for your input, Mark.

Do you know if that sender location (test port) is a high pressure location also?
Could I "blow out" a sender from the pressure?

I did have my guage do some weird stufff the other am. I remote started it and let it idle for just 5 minutes or so and came out and the gauge was allready above 220*. I put the key in and when I started moving it jumped a bit and went up and down and then settled on cold as I got moving. It must be moisture in the wire/connections or a spot where temp or abrasion has compromised the wires' insulation.

Still, I am going to do the maint that I listed above and we'll see. If it don't work I will be back here whining about it I'm sure.

Thanks again!!!

 

That port can see a maximum of 330 PSI. I have not heard of that damaging a sender.

 

I looked at the sender today and, yes, I guess it would be unlikely to blow that brass slug out of a threaded hole.

Thanks again!!!