Noisy 700r4

[87Suburban]

Hi, i have a 87 Suburban with a TH700-R4 and the transmission ran low on oil for a couple of miles on the hightway. When i got back in the city, I added a bout on liter but now the tranny seems to be making a humming/grinding noise in first and reverse. The shift from first to second also seems to be a bit harsher then before. Other gears seem to be ok. The transmission does not seem to slip in any gear. The oil is brownish but was like that when i bought the truck over a year ago.

Should i change the oil and filter or is the tranny shot ? Can i run the truck in its state for a while ? Will towing something in 3rd or 4th gear ok or will i kill the tranny ?

Thanks for you help.

[Crosley.In.AZ]

Do you know the mileage on the trans?  If it is high miles I'd leave it alone.

Do not tow in OD with a heavy trailer.    A light trailer is fine for OD on flat ground.

Noise?  could be a planetary set, pump noise, bearing noise in the rare of the tranny....

[87Suburban]

The millage on the trans is unknown, the truck has over 350 000 km so i doubt that the trans is orgininal.

So you don't think changing the oil and filter is a good idea on a high millage trans ?

The noise seems to be coming only in first and reverse. So i hope once its in 2nd or 3rd, the trans feels better.

I was aware of the weak OD gear, so i always try to avoid towing in OD, i only use it on flat ground. The only thing i tow right now is my 20ft boat...id like to get a couple more runs before the summer ends .

[entodad]

The millage on the trans is unknown, the truck has over 350 000 km so i doubt that the trans is orgininal.

So you don't think changing the oil and filter is a good idea on a high millage trans ?

The noise seems to be coming only in first and reverse. So i hope once its in 2nd or 3rd, the trans feels better.

I was aware of the weak OD gear, so i always try to avoid towing in OD, i only use it on flat ground. The only thing i tow right now is my 20ft boat...id like to get a couple more runs before the summer ends .

I agree, don't try to tow a heavy trailer in OD, I did and got a burnt OD clutch pack,  400$ in parts later it runs fine, but that is with me doing all the work and teething on rebuilding along the way
Doug

[Crosley.In.AZ]

The millage on the trans is unknown, the truck has over 350 000 km so i doubt that the trans is orgininal.

So you don't think changing the oil and filter is a good idea on a high millage trans ?

The noise seems to be coming only in first and reverse. So i hope once its in 2nd or 3rd, the trans feels better.

as I mentioned  the noise may be a planetary unit.... the one in the rear of the tranny. I

t functions in first gear, reverse and O-Drive