I'm not sure if richmond makes 3.90's. The FRPP are the best. I've changed gears in four IRS Cobras and most were dead on with a .03 pinion shim and no gear noise. I've heard other brands are usually out quite a bit. I haven't heard that FRPP were coming out with 3.90's. I need a set of gears pretty quick thanks to my dumb ass dealer.
I had the broken TOB retainer problem on my 03. I took it to this dealer because my buddy has used them with good results. They would fix things that he didn't even have the car in for. When the TOB retainer is broken, they have to replace the whole transmission. When I went to pick it up they informed me my differential was leaking. I knew I "may" have had a leak. I noticed a very small film of oil on the pumpkin. No drops, drips or streams. The dealer knew I had 4.10 gears. They told me that my pinion nut was loose and asked me who did the gears. I told them I did and they went on telling me about the crush sleeve. I know about the crush sleeve. You have to use over 100 ft-lbs. to crush it but you have to check the free run torque with an inch-lb. meter. I installed new bearings and specs call for 16-20 in-lbs with new bearings. I went a little too far and was at 22 in-lbs. I really doubt the nut was loose. They said they installed a new seal. I really don't see how they could have tightened up the nut properly with the half shafts still in the rear. I have also heard you should not reuse the crush sleeve. I was worried about this and was afraid the nut was either going to be too tight or loose. I was under the car the other night and I now no longer have a very slight leak, I have a geiser. It really pisses me off. I didn't not ask them to touch this and it shouldn't have been repaired under warranty because I had installed 4.10 gears. Crap like this will kill Ford. I think they said the nut was loose so because they had to put a cause on the warranty repair. Damn.
I am trapping at 7k revs in third in an 1/8 and the same revs in fourth on the 1/4. I think I may be losing a little pull at the end so I though I would drop down to 3.90's. I can fix the leak while I'm doing the gears. I could take it back but they'd just do the same stupid thing they did before. I really thought the film I had on the pumpkin was from the grease I put around the seal when I installed the 4.10's and is was breaking down due to the heat.
At least you can replace it easy enough. What I do is use a standard nut to winch down the crush sleeve most of the way, and then crank it the rest of the way with the new nut a little at a time. Never back it off.
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