Good evening,
This is my first time posting; just looking for a sounding board as I’m facing a bit of a dilemma.
I just (in the last 10 days) got my 89 727 truck back from the transmission shop. It Now has a respectable 3speed in it. New tq, billet planetary, and some valve body work done. The plan was to put a a518 in it but after 3 months of searching we couldn’t get our hands on a 4x4 core. This past week I lost the rear pinion seal, in a spectacular manner and I fried the pinion bearings. I ordered up a bearing kit, tore it down and found the ring and pinion aren’t exactly fantastic. Not surprising but really shitty news as 3.07 for a Dana 70u are made of unobtainium.
so this leaves me at a bit of a crossroads; if I gear it to a 3.54 The truck will be screaming at 70mph with 33s. I really don’t want to do a transmission swap as I just spent 3600 bucks and a year waiting on this 727. If I jump to a 35, I have to lift a truck I really wanted to leave alone, plus the 33s have around 6000 miles on them. I could reuse my 3.07 gear set, however the case hardening is work through on the pinion.
mostly wondering if I’m overlooking an option, and what a fresh group of eyes might see that I’ve overlooked. Thanks all.

 

If you haven't got past this....

The 3.07 Dana 70 diffs aren't that hard to find. I bought one complete with springs for $200, and another was gifted to me in a parts truck because the PO had already taken everything else he wanted.

I still see ads around for them. There is a reliable external casting 'tell'. Usually no mention of the ratio because sellers know it reduces the value.