Re-Gearing 7.5 LSD from 3.73 to 3.08, manufacturer recommendations for Ring and Pinion Gear set.

[bhgl]

Howdy folks,

I'm looking into re-gearing my rear axle from 3.73 all the way down to 3.08. The truck spends most of its time on the highway, and basically never towing, so for fuel economy purposes it's the right move. I'm mostly looking for manufacturer recommendations, I've seen a lot of Yukon Gear and Axle, but USA Standard seems to be manufactured by the same company. Some folks insist on going with actual OEM, or Ford racing parts, but I can't seem to find any at reasonable prices.

Unfortunately, at this ratio, and with an LSD there are no options for a junkyard pull, not to mention the yards up here in the North Ontario are pretty bare and far between, finding a truck with a relevant axle to steal the gear set from is going to be a headache as well. Relatively speaking, the gear sets are pretty affordable new.

I'll most likely be doing this swap, backlash and pinion depth adjustment included, myself depending on how many round-tuits I have on hand. Otherwise there's a 4x4 shop local to me that does good work so I'll take the full axle over there and pay the piper.

 

[sgtsandman]

Doing a gear swap is a very frustrating and time consuming process. To get a feel for the job, check out the video series Eric the Car Guy or ETCG1 (same guy but I don't remember which channel) did on a fox body with a Ford 8.8. It was a few years ago, so searching for Ford 8.8 on either of his channels will help you find it.

It's worth the work, if you have the time and are patient, but it isn't a job where you can just swap the parts and be done.

 

[BlackBII]

I have used Yukon gear sets and install kits and they are great. I have the factory service manual that outlines the removal/installation process if you want some pics of the relevant pages.

 

[bhgl]

Doing a gear swap is a very frustrating and time consuming process. To get a feel for the job, check out the video series Eric the Car Guy or ETCG1 (same guy but I don't remember which channel) did on a fox body with a Ford 8.8. It was a few years ago, so searching for Ford 8.8 on either of his channels will help you find it.

It's worth the work, if you have the time and are patient, but it isn't a job where you can just swap the parts and be done.

It's definitely the time commitment that is the limiting factor, I'm not opposed to just throwing dollars at it and getting the whole rear end refreshed while it's at the shop.

But seeing as my truck only has 80 000kms on it, there's a lot of life left in the components. I just want to change the ratio overall.

 

[bhgl]

I have used Yukon gear sets and install kits and they are great. I have the factory service manual that outlines the removal/installation process if you want some pics of the relevant pages.

If you could send me those pages relevant to a 7.5 LSD that'd be amazing! I'm glad to hear the Yukon Gear products are good because they seem to be the most ubiquitous.

 

[sgtsandman]

It's definitely the time commitment that is the limiting factor, I'm not opposed to just throwing dollars at it and getting the whole rear end refreshed while it's at the shop.

But seeing as my truck only has 80 000kms on it, there's a lot of life left in the components. I just want to change the ratio overall.

With a lot of luck, you may be able to just swap the pinion and ring gear with the original spacers and shims. I'm rarely ever that lucky and when I go to do mine, I have a front AND rear differential to swap.

 

[bhgl]

With a lot of luck, you may be able to just swap the pinion and ring gear with the original spacers and shims. I'm rarely ever that lucky and when I go to do mine, I have a front AND rear differential to swap.

Man, wouldn't that be nice!

 

[scotts90ranger]

I have used Yukon gear sets and install kits and they are great. I have the factory service manual that outlines the removal/installation process if you want some pics of the relevant pages.

As with many companies I've heard Yukon has gone down hill some in the ring and pinion department... that said everyone is stopping making everything so everything is a crapshoot and hard to find...

Hopefully you're planning on a ~25" tall tire with 3.08 gears, I've ran them and they were fine with a 195 75 14 tire size with a 5 speed 4 cylinder but that was about the limit I'd want...

 

[bhgl]

As with many companies I've heard Yukon has gone down hill some in the ring and pinion department... that said everyone is stopping making everything so everything is a crapshoot and hard to find...

Hopefully you're planning on a ~25" tall tire with 3.08 gears, I've ran them and they were fine with a 195 75 14 tire size with a 5 speed 4 cylinder but that was about the limit I'd want...

That really does seem to be the case when it comes to vehicles parts these days, everything seems to be in short supply, or only available through some backdoor website for licensed dealers.

I'll be running 3.08s with the stockish tire diameter of 27.4 inches. I've got some 205/70r16s lined up to install. Thankfully I'm running the 3.0 V6 so I have some additional grunt, albeit not a lot more.

I'm really not concerned with acceleration short of being dangerously slow, but I'll take the a hit in performance for that sweet sweet MPG.

 

[pjtoledo]

12 Tech Tips For Differential Assembly & Setup (yukongear.com)

 

[Roert42]

"I think last time I bought gears I went with Richmond gear. Only was able to put a 1000 miles on them before I got rear ended, so can't speak to their longevity.


Too bag you don't have a 8.8. I have a set of ford 8.8 gears in my garage I took out of an F-150 (swapped form 3.08 to 3.55 and installed a trakLok at the same time.). If you decide to swap to an 8.8 when you swap ratios, let me know, I have the factory 3.08 gears and an open carrier.

There is a book called "Ford Differentials, How to Rebuild a Ford 8.8 and 9" that is pretty detailed. Worth a look. Would be worth a look. Not familiar with the 7.5, but concepts are similar for most diffs.

You need a good amount of special tools to do the job by the book, but can be done without them too if you get paid by book instead of by the hour.

 

[pjtoledo]

like the ability to apply over 400 lbs-ft of torque on the pinion nut.

 

[Roert42]

like the ability to apply over 400 lbs-ft of torque on the pinion nut.

I sheered a 3/8" drift pin off that I was using to hold the pinion flange in place while I torqued the pinion nut down. Was one of those cheap green HF ones.

Ended up making a plate that bolts to the flange to hold it in place.


Forgot about that.

 

[Uncle Gump]

I have the OTC Big Blue Bar. I've had it for years... don't remember exactly what I paid but today's price on the only one I could find in stock is north of $1000. WTF!!!

 

[bhgl]

Doing a bit of reading today, I've struggled to find the 3.08 gear set being used with an LSD carrier in the 7.5. Short of having all the parts in my hand to compare, does anyone know if the LSD carrier will even work a 3.08 gear set?

I seem to remember SN95 mustangs having LSDs and 3.08 gear sets, but I'm having trouble confirming.