L322 250 miles towing caravan (big hills) - trans failsafe ..

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lenb

lenb

Active Member
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189
Location
Leicester, UK
250 miles towing caravan (big hills) - trans failsafe ......
........ after arriving at destination and setting up and then driving solo. Cleared with iid (forgot to save log but indicated speed sensor - I think - ) and no problems for rest of holiday including return journey home and total mileage of 700 miles. Did a full gearbox oil change 12,000 miles ago but am now paranoid 'rumble' will return (or can I hear road noise). Can I expect gearbox to need reconditioning soon? Just gone over 140,000 miles
 
The V8 gearbox is certainly less prone to rebuilds. But tbh, any auto trans with 140,000 miles on it, stands a fair chance of needing a rebuild at some point.
 
Did you drop down 1 gear in your auto, manually when towing? Here our auto trans has a tow/haul mode. Meaning you don't go into over drive (6 speed auto only goes into 5th ) Owners manual usually ( at least here) say don't use overdrive when towing.
 
I must admit I left it in Drive for the whole journey - the last 40-50 miles were on really steep and frequent gradients. At one point the vehicle smelt really hot - which must have been the box as engine temp was fine. The caravan was the best part of 1900kg and I probably went a little too quick. On my return journey home I used it in manual for the hills (different route but still long drawn out gradients) as I was a little paranoid about getting the problem again. Once I hit the M5 I left it in D again and watched 'live values' on my iid tool: oil temp was around 102-104 degs and the gearbox temp was around 89 degs.
 
lenb said:
I must admit I left it in Drive for the whole journey - the last 40-50 miles were on really steep and frequent gradients. At one point the vehicle smelt really hot - which must have been the box as engine temp was fine. The caravan was the best part of 1900kg and I probably went a little too quick. On my return journey home I used it in manual for the hills (different route but still long drawn out gradients) as I was a little paranoid about getting the problem again. Once I hit the M5 I left it in D again and watched 'live values' on my iid tool: oil temp was around 102-104 degs and the gearbox temp was around 89 degs.
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Don't know how your temp gauges work, but is that trans temp gauge sensor in the trans, before the cooler or after the cooler. Those temps are C I take it, and if they are look to be rather high.
Trans 192.2f and rad 215.6f is very hot when 160-180F is recommended operating range. You may of toasted that transmission
 
Cooling strategy does not kick in until 140 degs C - which suggests that under that is ok. Considering I was towing a 1900 kg caravan at a constant 60 mph then perhaps 104 degs C is not so bad after all? Cooling strategy did not kick in at any time including my outward journey.
All the readings were taken with my iid diagnostic tool, as to where the sponsors are located I'm not sure.
 
Your transmission uses an oil-to-water cooler which is fed coolant from the engine radiator. The engine coolant operates at a temperature of around 100-110°C so the transmission fluid will run at around the same temperature. People often comment that this feels intuitively wrong (i.e. too high) but that’s what it was designed to do. As you mentioned, it states in the workshop manual that if the transmission sump oil temperature (that’s where the temperature sensor is) exceeds 140°C then the ‘cooling strategy mode’ kicks in (inhibiting upshifts, etc.) but I suspect this mode is actually initiated at a lower fluid temperature than that and most report that it certainly happens before any overheat message is flagged.

Phil
 
Bemble said:
Your transmission uses an oil-to-water cooler which is fed coolant from the engine radiator. The engine coolant operates at a temperature of around 100-110°C so the transmission fluid will run at around the same temperature. People often comment that this feels intuitively wrong (i.e. too high) but that’s what it was designed to do. As you mentioned, it states in the workshop manual that if the transmission sump oil temperature (that’s where the temperature sensor is) exceeds 140°C then the ‘cooling strategy mode’ kicks in (inhibiting upshifts, etc.) but I suspect this mode is actually initiated at a lower fluid temperature than that and most report that it certainly happens before any overheat message is flagged.

Phil
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Ha Ha - Thanks Phil
I was just about to post a link to a post of yours on range rovers.net in July 2015 saying just that :)
 
lenb said:
the last 40-50 miles were on really steep and frequent gradients. Once I hit the M5 I left it in D .
Click to expand...
from leicester ,on m5 gather you went south prob kernow,?some bad hills over/by bodmin remember blowing a top hose off my 91 (j) 3.9 vogue classic towing my van abt 16 years ago oh the good old times & to top it off it peed down all week :(
 
tomcat59alan said:
You went south instead of north Wil, it hardly every rains here.:D:D
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Yep I went to Woolocombe - North Devon - hadn't been for about 5 years so decided to use my Satnav! Big mistake because it took me off 2 junctions too early and up the 'wrong' hills. Have a 19 year old disabled son so have all his heavy gear - tin tent just the job :)
 
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