Rob Posted October 4, 2010 Share Posted October 4, 2010 This new R612 truck that I have has an E6-315 engine, RTO-12513 transmission, 3.87 rears, on 11RX24.5 rubber. Got to play for a couple of hours with it today and have made some discoveries. The trans shifts very crisp and precise as is the clutch in operation. There is no noise from the throwout bearing, or driveline. Down the hiway almost against the governor, the speedometer is reading right at 75mph. I'm wondering how close it is. There is no abnormal shaking at any speed, nor does the truck ride exceptionally rough. The winch really has a grinding sound when the cable is run out, or in. The problem is traced to all four pillow block bearings supporting the jackshafts that support the chain sprockets for driving the winch are just plain flat worn out. I don't think they have had any grease for quite some time although there are plenty of zerk fittings. The seam sealer is busted up pretty bad in the rain gutter so that will need replaced and I'll probably paint the roof as there is surface rust needing cleaned up. The rooftop clearance lamps are in bad shape but I have new OEM ones I may use. I can get used to the power steering.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/ Share on other sites More sharing options...
Superdog Posted October 4, 2010 Share Posted October 4, 2010 If I remember right,the standard spec for a 300+ powered truck was a RT1110 trans,with 3:65 rears with 20 inch rubber or 3:87 rears with 22 inch rubber.This would give you around 68 mph at gov.speed.With your RTO12513,you should be able to get close to 80 mph. Quote Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64745 Share on other sites More sharing options...
Rob Posted October 4, 2010 Author Share Posted October 4, 2010 If I remember right,the standard spec for a 300+ powered truck was a RT1110 trans,with 3:65 rears with 20 inch rubber or 3:87 rears with 22 inch rubber.This would give you around 68 mph at gov.speed.With your RTO12513,you should be able to get close to 80 mph.Thanks Mike, I suppose the mechanical speedometer is somewhat accurate then. The truck is a 1980 model. It has Budd hubs on the front, and five spoke Dayton's on the rear. Were 22" rims prevelant that late? All eight of the drives are Accuride rims, (8.25X24.5) and were made in August, 1995, so known not original to the truck. All the tire are are Kumho, and General radials in good condition.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64746 Share on other sites More sharing options...
Lmackattack Posted October 4, 2010 Share Posted October 4, 2010 that engine and trans was a common OTR set up. Kanzlers valuliner with that steering box on it that we need to get off. has the same specs except it has 3.87 rears. If I recall The truck could hit 75MPH on the hiway. Quote Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64750 Share on other sites More sharing options...
terry Posted October 4, 2010 Share Posted October 4, 2010 Depends what you call against the govenor, i had a Dm with a mack 12 spd overdrive and with 4.17s 22.5 tires it would bury the 80 mph speedometer at 2300 rpm. terry Quote Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64768 Share on other sites More sharing options...
Rob Posted October 4, 2010 Author Share Posted October 4, 2010 Depends what you call against the govenor, i had a Dm with a mack 12 spd overdrive and with 4.17s 22.5 tires it would bury the 80 mph speedometer at 2300 rpm. terryAssuming the mechanical tachometer is 1/2 way accurate, about 2000rpm.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64771 Share on other sites More sharing options...
Bollweevil Posted October 5, 2010 Share Posted October 5, 2010 This new R612 truck that I have has an E6-315 engine, RTO-12513 transmission, 3.87 rears, on 11RX24.5 rubber. Got to play for a couple of hours with it today and have made some discoveries. The trans shifts very crisp and precise as is the clutch in operation. There is no noise from the throwout bearing, or driveline. Down the hiway almost against the governor, the speedometer is reading right at 75mph. I'm wondering how close it is. There is no abnormal shaking at any speed, nor does the truck ride exceptionally rough. The winch really has a grinding sound when the cable is run out, or in. The problem is traced to all four pillow block bearings supporting the jackshafts that support the chain sprockets for driving the winch are just plain flat worn out. I don't think they have had any grease for quite some time although there are plenty of zerk fittings. The seam sealer is busted up pretty bad in the rain gutter so that will need replaced and I'll probably paint the roof as there is surface rust needing cleaned up. The rooftop clearance lamps are in bad shape but I have new OEM ones I may use. I can get used to the power steering.Rob That sounds about right for road speed. holcombtrucks.com has an on line calculator that I use. To use their calculator, you need to know the tire diameter. I think a 24.5 will measure about 41 in. Check one to be sure. Quote Link to comment https://www.bigmacktrucks.com/topic/16001-how-fast-will-this-sucker-run/#findComment-64782 Share on other sites More sharing options...
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