Renault 21 Turbo UN1 box OIL LEAKS

[Ian Anderson]

How do most of you find these boxes are they oiltight or only oiltight when the oil is on the outside? (Another forum seems to think Renault = leaks)

I have managed to use 2.5 liters of 75/90 oil in about 100 miles and it seems to be dripping all the time. (Rear of car has a mist covering it after a few miles drive)

There is a small weep from the roll pin that holds the drive shaft - need to give that some silicone to stop the stuff, once it has run along the splines, from escaping.

this would also then mean that the internal CV boots will have a mix of oil and CV grease in them - is this normal or should there be a bung of some sort on the axle side of the splaines on the adaptor?

Also it appears to be weeping from the case join at the bottom - is there supposed to be a gasket in there?

The gearbos is said to be brand new unit from Renault dealer bought by previous builder about 15 years ago and never turned a wheel in that time but also never been filled with oil so perhaps some seal needs to take a drink and then seal itself (I hope but don't expect it to happen)

Also how low could the oil go before damage in normal road driving? Still running in the motor so no major bursts!

Thanks
Ian

[RichardH]

I gather from making enquiries that they are prone to leaking from drive shaft seals - mine appears to on n/s. Just keep checking level. Does anyone have a method of (quickly) checking oil level other than removing plug? I have heard of having a sensor fitted, but have found no info about it.

[Howard Jones]

Ian, The CV adapter is sealed on the end that goes into the gearbox so oil form the gearbox will not get into the CV joint.

The weeping pin will flow a moderate amount of oil and with it Turing at the speed of the wheel it will throw a lot of oil all over the rear of the car.

Clean up the adapter and the inside of the pin and then pump a little RTV into the pin from on side and wait until it flows out the other.

The mating surfaces should not leak. Make sure all the bolts that hold the halves together are tight. Also check the rear cover to see if its is leaking from the gasket and that all it's bolts are tight.

The R21 holds just a little less than 1 US gal. I wouldn't want to run it at anything less than 80% full. It is best to keep it topped off if you can.

Mine has a bung on the top of the 5th gear rear cover. I can open the side fill that on my car has a AN fitting threaded into it and pour oil into the top while waiting for the over flow to run out the side through a 90 degree piece of tubing screwed onto the AN fitting. Nice and clean fill procedure.

[RichardH]

Originally Posted by Howard Jones

Mine has a bung on the top of the 5th gear rear cover. I can open the side fill that on my car has a AN fitting threaded into it and pour oil into the top while waiting for the over flow to run out the side through a 90 degree piece of tubing screwed onto the AN fitting. Nice and clean fill procedure.

Hi Howard - Any pics or drawings of this mod?

regards
Richard

[Ian Anderson]

Howard

Perhaps a different make of adaptors
It has a flange to attach the CV
This is then conical to the "pipe like" part where there are splines on the inside.

Taken off the 'box you can see straight through - I would perhaps have thought a seal of some type just after the splined portion (insidr the conical bit)

It also seems strange to me that the seal is onto the outside edge of the adaptor and not onto the gearbox shaft before the splines - no need to seal the splines / ends and roll pin holes

But then again this is a DAX and uses VW Transporter drive shafts and CV's

Ian

[Tony Hunt]

Ian,
The roll pin hole can leak if the gap in the pin isn't facing away from the box. This is a common fault when putting on the adapters, pointed out to me by Brian Mg when we pulled my box last winter.
The box halves need quite a bit of gunk on the faces when reassembled, and I wouldn't be surprised if the stuff has dried out while the box was in storage.
The only acceptable rate of leakage is - none. You can't afford the cost and accident damage of even risking the box seizing at speed, and Sod's Law says that the leak will get worse when you are least able to check it.
My advice, for its 2c worth, is to pull the box and get it to CTS in Markyate. Bernie Braden and Stuart Burchall have Renault box experience (my two!) and will split the halves, renew the gaskets and seals and reinstall the roll pins quite cheaply. They aren't 140-odd miles away in Telford, either!

[Howard Jones]

Ian, Yes indeed your adapters are different than mine. Run a bead of RTV around the end of the stub-shafts inside the adapter before you mount the CV joint to seal the adapter and prevent the CV grease from being contaminated with gearbox oil. Let the RTV setup overnight before you mount the CV's and pack them and the adapters with grease.

I think it is a good idea to have the gaskets replaced if they are flowing a lot of oil. (like yours) The fear is that a segment of gasket will fall out of the bottom flange and you loose all the oil very quickly and burn up the gearbox.

[Dave Bilyk]

On my UN 1 gearbox, one side leaked because the roll pin was broken. The reason it was broken was due to suspension setup. As the suspension moves through its travel, the drive shaft extends and compresses. If it is not set correctly, the drive shaft(s) may compress fully on suspension droop, in this case the load is carried by the roll pin, and it can break. Check by jacking the car up to droop the suspension fully, then check if the drive shaft moves freely in and out. If it does not, or the inner hub can move in and out on the gearbox output shaft, the roll pin is broken. In this case, the roll pin needs to be replaced, and the suspension arms need to be lengthened (rose joint adjust) to avoid compressing the drive shaft fully.

Dave

[Ian Anderson]

Dave

Thanks for that I'll double check but I did once before and there was ability to move the driveshaft both in nomal and droop position

Howared yes I tink a strip and reseal is required

Ian

[shoffman]

Maybe I'm out of my league here but as the owner of a Lotus Esprit I am used to oil leaks. Sigh......

With the Renault trans oil leaks from the transaxle area usually imply that you need new side seals. Lotus sells a double lipped beast that works quite well but costs $$$. JAE is a good alternate source. With respect to the roll pins; the Lotus application actually uses two. An outer and an inner that are driven in with the cut/split at 180 degrees. I believe they are like 4mm and 2 mm pins. If you coat them with RTV when you drive them in they won't leak oil nor are they as likely to break as you have twice the thickness.

I've never seen the case leak between the split halves as I am sure they don't use a gasket. Just the red anerobic(sp?) jam that seals them together. There is an O ring on the input shaft tube that can go bad but the means oil in the clutch area. There is a gasket between the bellhousing and as well as the overhung fifth gear casing. Perhaps other applications are different.

If my Lotus is parked for more than a month or so it almost always starts to leak oil out of the side seals. There is a special seal driver that ensures the new seals go in square. Otherwise your new seals will probably leak.

My $.02

Steve

[RichardH]

Good One Steve.
If it is of use, I noticed my seals were leaking only after a 6month winter lay-up, so maybe that is part of the problem. Any ideas of a fix, folks, apart from dont lay it up for 6 months?