Installing RTO 915 into Volvo F7

Hi all,
Finally, I am getting rid of the R52 gearbox out of my F7 Volvo (probably one of the worst boxes) and converting with an RTO915. The 915 came out of a burnt truck so the air lines and in-cab controls were burnt. Can anyone tell me where they go and what they do?

Cheers, TonyD

same post in General Truck Talk

Give me a day mate and I'll take a photo of one of mine, and guide you through it a bit. I'll be at work tommorow and I've got the floor out of my Reo which has the samr box.

Tony, have you ever tried the SR61 and twin plate clutch which was fitted to some late F86 and F7. The splitter has a quick action and transforms the truck, although being syncro the rest of the box is still slower than RR. Twin plate clutch reduces pedal presssure.

Thanks Mammoth. I am open to correction if I am wrong.

As I see it the SR61 is the direct drive earlier version of the SR62. Either would be good. I prefer to go with the overdrive but the Volvo boxes seem to give trouble in the overdrive section. The 6 in 61 and 62 stands for 600 ft lbs torque while the 5 in 52 is 500 ft lbs. I think the 52 cannot take the torque of the motor when the box gets old. With the 900 ft lbs RR, which is almost double and a massive overkill, it can stand any amount of torque overload the engine and my driver can give it.

The history is that I bought the truck almost 4 years ago and it went well for 2 years. In the last 18 months I rebuilt the box 3 times. This is the 4th time.... no more.

My decision evolved because I already own an RTO915, which I lent to a mate but now it is taking time getting it back. I was able to buy one from a wrecker at a good price, one that came out of an F7 (lucky for me). All the messy conversion work has already been done (different: clutch, throw out & bearing, input shaft, bell housing, spigot bearing adaption, slave adaptor plate, gear linkages etc). They will even exchange the tail shaft, if they have one that fits.

All is going well so far except for the air hoses and this continuing wet weather-no shed for us poorpers.

I already have the twin plate clutch, which is not a problem.

Cheers, TonyD

According to an early Volvo book the R60 was matched to the TD100A motor and the R61 was developed for the TD120 (330 hp) motor, so is well over engineered for the TD70F. The SR61 has the split overdrive, I think the 62 was a heavier ot updated version. As you say after 3 rebuilds you must be getting tired of looking at the Volvo job and the RR is already in your shed. I have heard that to rebuild a Volvo box successfully you need some very special tools to get it right.

Thanks mammoth. Learn something new every day. Never know where all the answers are.

We didn't need any sophisticated special tools. It was rebuilt by 3 different repairers including me. Volvo do not rebuild the R52 nor have parts for them. If they did, it would cost a fortune.

One repairer does the 60's for $6500 but others do them for about $14000-$18000. We take shortcuts e.g. correct end-float backlash etc., size change of the case including stretch, twist etc. Doing all these checks would cost a fortune and fixing them would render the gearbox unrepairable due to the enormous cost. Some gearboxes can tolerate these changes. I think the 52 is great when new or near new but is under designed for the long term.

Ol' mate had a G88 with an R62 with overdrive. I think it was factory fitted. He repaired the overdrive a couple of times and eventually left it as direct drive for city work. It seemed to be common knowledge that the R62 OD do not last.

I better get off my soapbox. Cheers, TonyD

Thanks to everyone who sent in suggestions, information etc.

Now I'll ask you to dig deep. The RTO915 is in, the clutch modified and fitted, linkages modified and fitted, air lines fitted as per schematic etc. Guess what!!! We cannot select ranges correctly. What's more select deep reduction to get high range, select high range to get nothing. Yes, you will all say "Tony you got your air lines crossed." But as I said they are installed as per the schematic. We also tried to swap the lines around - no avail.

One suggestion is that I inherited an hybrid. That is someone has mixed and matched bits from different gearboxes to build something new.

Can anyone offer suggestions as to what is going wrong??????? Thanks!!!!!! Tony

Can't help with that problem but as a post script I have just read an F7 road test in 1980 B&T. The 4x2 had the R52 while the 6x4 and 8x4 had the SR62. The 4x2 had plain chassis rails while the others had the specially rolled rails with thicker flanges. So that explains the confudion of spec.

Tony, if your selecting deep reduction and your getting high range, the thing is plumbed up wrong. Forget the deep reduction switch for a minute, put the air supply from the very front of the shuttle valve where it splits into 2, one into the supply side of the deep reduction valve, one into the supply side of the range change. Get the air pressure up, from memory the gearbox goes into low range when the air supply is blocked, so with nothing hooked up it should be in high range, air should come out of the range change valve if it is in the up position, then no air in the down position, if this is the case, hook up the airline from the range change valve to the rear port on the shuttle valve. Diconnect both the air lines from the shuttle valve that go to the range change cylinder, which is the one at the top drivers side of the gearbox. Try the range change again, when the valve is in the up position, air will come out of one air line and vice versa. I'm pretty sure the air line at the rear of the shuttle valve goes to the rear of the range change cylinder. It doesn't really matter, once you get air coming out of either air line when the range change valve is changed, hook up the appropriate one to get into the range that the valve is in. Once that is sorted, just hook the delivery air line out of the Deep reduction valve to the rear port on the Deep Reduction cylinder which is on the bottom passenger side of the gearbox.

Thanks Mammoth.
Did the 4x2 F7 have the TD70 donk putting out 500 ft lbs of torque and approx 213 or 224 HP therefore R52?
Did the 6x4 & 8x4 have the TD100 eng with 600 ft lbs torque and approx 270 Hp therefore R62?
I had the R52 behind the TD70 eng pushing a 6x4 tipper. I think the power was still too much for the R52 to continue to perform forever.

Anyhow the R52 is out now. Now I have RTO915 problems. :'(

Cheers, Tony