I have a GT225. Follow the manual's recommendations.

I have never noticed the transmission on mine get very hot (I'm sure it gets warm, but never enough to make me notice it). It might be the previous owner put the wrong type oil in it.

How warm will the case get?? Depends on factors like today's ambient air temp, and how hard are you "working it". Also will depend on how high RPM your engine is turning. With hydrostats, you want to run the engine very near the wide open throttle position (or at least close to 75% to 90% max RPM). Engine RPM = hydrostat cooling fan RPM. Need to keep the fan spinning fast, even if you don't want to go fast across the terrain. Don't lower your engine RPM to travel slowly, instead, "feather" the hydro pedal or lever to go slow. The amount of heat a hydro can generate is going to be nearly the same at low engine RPM as it would be at high engine RPM because the amount of heat generated is dependent on the amount of work the transmission is accomplishing (torque). An engine with a lot of torque output might very well accomplish the same amount of work at a lower RPM, but, the transmission will suffer! Though it is doing the same "work" (as at a higher RPM), it is not "shedding heat" quickly enough (slow turning fan) and so the oil temp goes high enough to begin degradation through heat. If you run the RPM up high and feather the hydro control down some, transmission still accomplishes the same work, but now it can shed heat better because the cooling fan is moving a larger volume of air across the trans case. This is why debris (grass, leaves, dirt) is so deadly to hydrostats, the debris is "insulation"! As to the case temp you can expect.......about as hot as "3 minute old" cup of coffee if the day is in the 80s or low 90s and you are working it normally. If you are climbing steep inclines, a bit hotter. If you are towing a heavy cart, a bit hotter. If you are towing a heavy cart up a steep incline.....stop that! If you get to where the transmission seems to "lose its pull" (engine RPM is high but ground speed drops dramatically) the oil is probably degraded to the point of "foaming" (because of water uptake, loss of viscosity and, loss of additives) and should be changed. I know people may have their own opinion of "which oil is best". For my own use, 5 W 50, 10 W 50, or 20 W 50 (synthetic) Motor Oil would be satisfactory. Use the prefix numeral in deciding which you need based on the WARMEST expected temperatures you might encounter in your local area (high temp? choose higher prefix numeral). The suffix numeral will not make much difference except if you will use it in temperatures near or below 0 degrees F.

Go to this site and download your service manual and learn everything you need for that unit. If I were you I would do a full service on the GT. Fluids,belts,filters, and grease eveything.

Get the free manual here and just save to your computer. This is what I did and it worked out great.

http://www.deere.com/en_US/ProductCatalog/HO/servlet/com.deere.u90785.cce.productcatalog.view.servlets.ProdCatProduct?pNbr=SKU20859&tM=HO&link=enav

That is very interesting about your statement on the non contact thermometer - Ive seen some on craigslist recently - the ones with a lazer pointer.

I sold my 10 year old Scotts about 1 month ago and always wondered about the transaxle in it (T.Torq K-51). I almost NEVER ran my machine at high revs, forward worked great but reverse was wimpy (unless the engine was running at a higher RPMs). I never got around to changing it - because Ive heard different stories after the oil change (some good / some bad).

Regardless of these good /bad stories - All signs point to a properly re-lubed and adjusted tran-saxle running cooler and longer when changed and cleaned. I guess the problem with them - is getting under the tractor to give them a good cleaning... Any tips on that anyone ?

I was able to look at someone's JD a few months back (dont recall what model/transaxle it had) but when the tranny was removed I was a bit disappointed to see how filthy and clogged up it was. Not surprised mind you - but when you see something like that - you know the fan couldn't do an optimal job of keeping it cool. You could clearly see where the owner had washed down the tranny - and clearly see where he could never get to it.

Recently I bought a Case/Ingersoll which has a hydraulic trans (similar to a hydro in idea - but rather different in layout) this unit holds a LOT of oil in its system (about 6-7 quarts ) and I'm told that overheating the unit is "somewhat unlikely". It also has an aluminum oil cooler behind the grill / in front of the old Kohler engine with a fan spinning off the front PTO. Today I was able to see that my Oil cooler needs a good cleaning. (I think I'll have to be delicate with that cleaning).

But I have been wondering about somehow connecting an oil temp gauge to the oil reservoir in the tractor - just to watch and try to determine "what is normal". The problem is im not really sure where it would get installed, I was thinking maybe find another filler cap for the oil tank, drill it and mount a thermocouple in the oil cap hole. Or do the same with the wife's meat thermometer... (she wont mind).

Anybody else out there monitoring temperatures on trans-axles or engines? ... How have you done this ? Oh and it should be cheap ...

Good luck - dave

I have a 2000 GT235, B&S 18HP V-Twin Vanguard, K71B tranny, and 48C deck. I'll try to remember to take some IR readings with my Raytek MT6 the next time I cut - probably this Friday or Saturday. I'm only cutting about 1/3rd of an acre - mostly flat except for one slight hill. I still run it at 80+% WOT so the tranny fan has sufficient RPM to dissipate the K71B's heat. (Yea, I know. The GT235 is overkill for 1/3 of an acre. I originally bought the GT235 when I was mowing 1/2 to 1+ acres.)

Here is a link that might be useful: Raytek MT6

Thanks kdiller. The Raytek MT6 is exactly the non-contact IR thermometer I'm probably going to get. I've wanted to get one for quite a while, but the prices were always more than I thought I should spend. Prices have come down though and I think I'm going to get MT6.

Thanks also for the info deerecub and the other responses. I serviced the engine first and moving on to the other parts of the unit. Probably take me a few weekends, but I'll get through everything.

Here's some approximate TT K71B temps (in a JD GT235) using a Raytek MT6 under the following conditions.

Outside air temp was ~ 75º.

1) Mowed about 1/4th of an acre, generally flat property, normal to slow speed (mulching), both forward and reverse directions. Quickly shut off PTO, set the brake, engine running at about 1/2 throttle. Measured temps at multiple points underneath the tranny. (Temps on top of the tranny were lower.) Average temps were in the low to mid 120º's.

2) Next ran the GT235 rapidly forwards and backwards up and down a short 15-20% incline 4-5 times at WOT, PTO engaged. Quickly shut off PTO, set the brake, engine running at about 1/2 throttle, and checked temps underneath tranny. Maximum temp was 136º. Average was probably high 120º's. (I have the annoying and useless RIO bypassed.)

There's 334 hours on this GT235. At 250 hours the tranny oil was drained and re-filled with the JD recommended low viscosity HY-GARD.

(Sorry for not posting this sooner. Been sick for several days. On the mend now.)

Good info - thanks for posting. I'll post some as well when my Raytek shows up. From your data, I don't think mine is running any hotter. A web search found 112F as the threshold of pain for skin contact. Anything hotter and you want to pull away. 120s to 130+ makes sense. Not that hot, but you somewhat have to force yourself to keep you hand on it for a while. And your ambient temp at about 75F wasn't that warm so I would expect the tranny temp to rise some with increasing ambient temps. Once I get my Raytek, I'll see what I get with mine.

kdiller and nysff: I've had my Raytec IR "temp reader" for around 10 years now (we typically refer to it as a "thermo scanner" in our shop. I don't remember what the exact model # is. (and I keep it in my tool chest at work, so I can't access it today). I will try to remember to scan a "3 minute old" cup of coffee to see how close the analogy actually is. I find the thermo scanner to be very helpful for a lot of routine checks, as well as the "tough problems". For example, you get a multi-cylinder V engine in the shop with a "dead miss". You can scan each exhaust port on both banks to see how "warm" they are. The coldest one(s) are the culprit cylinder(s). This allows you to make a definite determination of WHERE you need to look further without having to go through the more advanced diagnosis procedures first (though you might still have to do "advanced" later). I have also employed it to check "pre-heating" temperatures when I preheat metal for certain welding repair operations. I guess the applications are only limited by your imagination (and of course, the upper and lower limits of the temp range of the thermo scanner).