3.0i Towing(ish) My R35

[7to3_enthusiast]

So...we can all do the easy math and know that this towing adventure was questionable at the very least. But it did get me a 1.25 hour trip to the track and back with the only mishap was overheating the trans temps while trying to keep pace with some friends towing with turbo diesels 80+ mph uphills (I asked them to go slow for little ol me ). When the trans overheated it locked me in 5th gear, but still managed to limp it into a shutdown gas station while having to make a u-turn going slightly uphill . Once I cooled it down and stayed at 60-65 mph there were zero issues.

This leads me to the reason I'm posting this. Has anyone who uses their x5 for towing more frequently looked into installing a larger oil cooler for the trans or adding an external oil cooler?

EDIT: The reason I ask is I'm going to change the fluids and replace the original oil cooler, figured I'd look into any documented improvements while it's down for maintenance.

[Bdc101]

How much do you think the trailer weighed? Your car is rated at 5,500lbs or 6,000 lbs towing capacity. I would guess that the car and trailer weighs no more than 5,000lbs (3,800lbs for the car plus maybe 1,200 for the trailer sound reasonable?). If the trans is overheating I wonder if there may be another problem. I don't think I have heard of overheating the auto tranny while towing before on this forum.



There is a transmission cooler built into the radiator of auto-tranny cars. I don't know how it could be broken other than being clogged, which seems unlikely. It is a good time to change the transmission fluid (since it overheated) and check on the status of that system. The cooling system is a ticking time bomb on these cars anyways, so you might want to consider an overhaul if the age of the components is unknown.



I tow with a manual trans, so I may not be much help on diag. I have never had any problems despite towing a 4,500lb trailer up a steep mountain pass with a car full of family and two paddle boards on top. WOT for 10+ minutes in third and fourth gears without a break.

[7to3_enthusiast]

Originally Posted by Bdc101

How much do you think the trailer weighed? Your car is rated at 5,500lbs or 6,000 lbs towing capacity. I would guess that the car and trailer weighs no more than 5,000lbs (3,800lbs for the car plus maybe 1,200 for the trailer sound reasonable?). If the trans is overheating I wonder if there may be another problem. I don't think I have heard of overheating the auto tranny while towing before on this forum.



There is a transmission cooler built into the radiator of auto-tranny cars. I don't know how it could be broken other than being clogged, which seems unlikely. It is a good time to change the transmission fluid (since it overheated) and check on the status of that system. The cooling system is a ticking time bomb on these cars anyways, so you might want to consider an overhaul if the age of the components is unknown.



I tow with a manual trans, so I may not be much help on diag. I have never had any problems despite towing a 4,500lb trailer up a steep mountain pass with a car full of family and two paddle boards on top. WOT for 10+ minutes in third and fourth gears without a break.

Uhaul lists their car hauler at 2210 lbs and the GTR is around 3900 lbs. So we're looking at a tad over 6k. It locked my gears out during a long pull uphill playing catchup around 75 mph. In all reality I think I was just asking too much of the cooling system at the time and I can't blame it.

I wanted badly to have a MT, but after looking for several months I had to settle with an AT. Nice find.

[Bdc101]

Aha, I guess that trailer is heavier than I thought. Perhaps you were just hitting the limit with the car. An external transmission cooler would probably be a good idea for future towing then. But a fluid change would probably be a good idea either way, since it has been overheated.



I was actually adamant on finding any manual-transmission vehicle that could haul my camper trailer. This was pretty much the only one that I could find that wasn't a soul-sucking diesel truck. The MTs actually have the highest tow rating of all of the E53 models, but only by a little bit (6,500lbs). Despite the tow rating though, I find it to be much more stable as a tow vehicle than much larger American vehicles, with much larger tow ratings, that I have towed with.

[Effduration]

Yeah that uhaul trailer is an absolute tank

OP- you were a tad over the limit (okay) and were betting your transmission with that race uphill. Change your fluid and hope..

A larger cooler might help, but a lot of E53 folks trailer w/ no pblms.

[nick325xit 5spd]

My two cents would be to just admit that you're not towing with a real truck and keep the speed down a little.

The super high stall speed on the 3.0i torque converter makes the E53 unreasonably lively for the dinky engine, but the trade off is always going to be trans temps.

[srmmmm]

U-Haul trailers are always heavier than you expect them to be. They're built to take the abuse of people who don't know how to trailer. Even a bare bones 5 X 9 open utility trailer is over 1200 pounds.


The OP didn't indicate which transmission he had, but towing at the max limit like that would make the convertor lock-up clutch a high wear point in the GM 5L40-e, possibly trashing the fluid and filter with debris.

[Attacking Mid]

Agree with others.... you're towing at/over the limits of the vehicle. You must take it easier. I towed near the limits pulling our travel trailer - even a 15 hour drive through the Rockies through Yellowstone on the way to Big Sky. We didn't baby it, but also didn't try to over-work it in the mountains. It did just fine.

AM.

[Bdc101]

AM, have you installed any external transmission cooler for your towing setup?



We MT guys may not have the overheating problems as the AT guys, but we also don't have the luxury of having a fluid line or pump that we can use for such a cooler if we were going to install one.

[7to3_enthusiast]

Thanks for the comments so far guys/gals. It sounds like after a fluid change I can get by just being more realistic with my towing speeds especially uphill.