I had been considering a gear change for a while now, and after a some debate, I settled on 4.88:1. The 5:13s didn't have the pinion engagement for towing, and that's part of the plan. 4.88s set the rpms right where they need to be for my turbodiesel, so I got on the phone to Reider Racing and ordered Precision 4.88s and an install kit.
How did it do?
Performance Report:
In a word, wow! If you put this thing in drive, you had better want to go forward. It's like I have it in 4-lo all the time. The Detroit chirps more frequently in turns, but it's not violent at all. Interestingly, in town performance isn't that different. Cruising on the highway is where these gears make themselves known. /forums/images/graemlins/grin.gif
75 mph @ 2400 rpm gives 5.5 - 6 psi of boost and 550 - 600 on the EGT. Locked up in 4th, lean into it a little bit and it's easy to gain speed on hills with boost topping out around 12 psi before the 700R4 tries to grab 3rd. Thank goodness I installed extra sound deadener some years ago; I think it would have been a little loud otherwise.
The real fun in all this was watching my friend set up the gears. I had never seen the guts of my 14FF disassembled, and had never seen a rear end set up. The attention to detail was awesome. Backlash is set at .010, and we ended up shimming the pinion to .023 to get a perfect pattern. Drive side was perfectly centered, and the coast side had the slightest bit of toe in. /forums/images/graemlins/peace.gif
My speedo is highly inaccurate now, and I need to rebalance my rear driveshaft. One mod begets another. /forums/images/graemlins/rolleyes.gif
After the 500 mile break-in, I'll see how well these BFGs can hold on to the pavement, and give a towing report.
...now if I could just find some time to install these 6.5TD injectors I have... /forums/images/graemlins/thinking.gif
/forums/images/graemlins/cool.gif
How did it do?
Performance Report:
In a word, wow! If you put this thing in drive, you had better want to go forward. It's like I have it in 4-lo all the time. The Detroit chirps more frequently in turns, but it's not violent at all. Interestingly, in town performance isn't that different. Cruising on the highway is where these gears make themselves known. /forums/images/graemlins/grin.gif
75 mph @ 2400 rpm gives 5.5 - 6 psi of boost and 550 - 600 on the EGT. Locked up in 4th, lean into it a little bit and it's easy to gain speed on hills with boost topping out around 12 psi before the 700R4 tries to grab 3rd. Thank goodness I installed extra sound deadener some years ago; I think it would have been a little loud otherwise.
The real fun in all this was watching my friend set up the gears. I had never seen the guts of my 14FF disassembled, and had never seen a rear end set up. The attention to detail was awesome. Backlash is set at .010, and we ended up shimming the pinion to .023 to get a perfect pattern. Drive side was perfectly centered, and the coast side had the slightest bit of toe in. /forums/images/graemlins/peace.gif
My speedo is highly inaccurate now, and I need to rebalance my rear driveshaft. One mod begets another. /forums/images/graemlins/rolleyes.gif
After the 500 mile break-in, I'll see how well these BFGs can hold on to the pavement, and give a towing report.
...now if I could just find some time to install these 6.5TD injectors I have... /forums/images/graemlins/thinking.gif
/forums/images/graemlins/cool.gif
