Do I Need A Transmission Cooler?

[Cephas]

I suspect I might need a bigger cooler for my m35.

Gearbox is fine over short drives, but after an hour at highway speed it starts to hold onto 3 rd and 4th right up to 4000rpm under low throttle.

Backing right off will get it to shift into 5th.

Does that sound like a heat issue?

If so, what aftermarket coolers are people using?

Do you bypass the cooler in the radiator, or run them in series?

Thanks.

[zei20l]

sounds fairly normal. the throttle is very sensitive.

however, its worth it getting additional cooling. run them in series, put the new one AFTER the factory radiator loop.

[Sunkist]

first things first..

change the oils in it to either Nulon AT fluid which is preffered, or nissans Matic J. both the transmission and transfer case will need to be changed(if not already done so).

then get a trans oil cooler, and link it in to the one thats already running through your radiator. you will notice a masive improvement.

hope it helps

[Sunkist]

sounds fairly normal. the throttle is very sensitive.

however, its worth it getting additional cooling. run them in series, put the new one AFTER the factory radiator loop.

how do you know which ones after? and why would it be important?

[zei20l]

take one of the hoses off, start engine, does fluid come out?

if you put it before, youre cooling the fluid only to heat it again. if you put it after the trans loop, youre cooling.

[Sunkist]

ahhh so if fluid comes out of the hose you take off when you start the engine, does this meand before or after?

[zei20l]

it means before, the fluid is pumped into the radiator trans loop.

its 1/4 auto trans hoses youll need. not cheap, but worth the mods.

i plumbed mine behind the LH headlight, there is a blank area in the reo bar that i cut a hole out to get the hoses through.

[Sunkist]

yeh ive done mine, but it might be worth checking whether ive got it the right way. thanks iain

[Cephas]

Already got Nulon AT fluid in it.

What make of cooler have you used?

[zei20l]

i have a 30cm x 12cm cooler with 1/4 fittings. seems to work fine!

im not running the intank trans cooler at the moment. waiting till my new radiator goes in.

if you do install one, check fliud levels afterwards as the new cooler will take some of the fluid volume

[pipster11]

wouldn't you put the new cooler before the radiator loop?

the rad loop is to regulate the temp of the fluid so you'd want the aftermarket cooler to drop the temps and the rad to bring it up to the correct temp

[zei20l]

then all youre doing it running it at the temp its at now, thus making the new cooler null.

if its after the stock cooler, the trans fluid still gets up temp quickly due to the radiator loop - and also cooled if required - but also cooled lower than the stock 'setting'. which is the whole idea.

[pipster11]

but its designed to use the oil at ~90°c

new cooler first drops the temps from "too hot" to "warm" then your actually taking heat from the coolant and putting that back into the trans oil

it takes the load off the radiator core and regulates the trans oil better

have a look at any stock 2 cooler setups like on most commodores, pretty sure its

edit: after a mid post research

http://autospeed.com/cms/title_Cooling-the-Trans/A_109772/article.html

this guy says in hot temps you can just bail on the stock one but if you see cold temps you'll want the aftermarket unit BEFORE the stock radiator one

[zei20l]

hmm i see your reasoning. ok, fair enough! ill try that one

when i get my new radiator in ill try it that way. cheers!

[Chris Rogers]

bigger cooler is better. have a 600x 600 one on my subaru and that keeps temps quite good and quite driveable. in my case I do not use the stock one in the radiator.

that said my 4spd box isnt entirely stock either. (after a $4500 rebuild.)

[Cephas]

Got one fitted today, which was good timing given the temps today...