Build thread - 3.08 to 3.42 front and rear gear change

[swathdiver]

Thanks for the info. I found more damage tonight - the flange that the brake backing plate/parking brake mounts to is bent on one corner. That seals the deal, I'm going to start my return/exchange with LKQ tomorrow and hope my second attempt is more successful. I'll do a lot more close inspection before I accept the next one.

On a different note, since I couldn't work on installing the new rear end tonight, I thought I'd work on replacing the rear u-joint. But I'm confused. In other threads about this swap, guys have talked about having to use a 1310 to 1350 conversion u-joint or switch driveshafts, but it seems like my stock driveshaft already is 1350. All the bearing caps measure out at 1.19 (1 3/16") dia, which is the size of a 1350, and the yokes on the 8.5 and 9.5 are identical. So it seems I could have left my old u-joint in there, but new Spicer on order now. Can't hurt to have a new rear u-joint. Just trying to figure out why some have had to do a conversion and I don't. Maybe they changed the size in the later years of GMT 900? Mine's a '13.

Should not need a conversion joint on a GMT900, all the 1500s use 1355 universals out back. Make sure your Spicer is for a 1355 and not a 1350, they are different.

When you get the replacement axle, inspect the cast parking brake anchor blocks too. I had them broken on my donor axles from being dragged around the scrap yard and had a tough time finding a replacement.

 

[Doubeleive]

Thanks for the info. I found more damage tonight - the flange that the brake backing plate/parking brake mounts to is bent on one corner. That seals the deal, I'm going to start my return/exchange with LKQ tomorrow and hope my second attempt is more successful. I'll do a lot more close inspection before I accept the next one.

On a different note, since I couldn't work on installing the new rear end tonight, I thought I'd work on replacing the rear u-joint. But I'm confused. In other threads about this swap, guys have talked about having to use a 1310 to 1350 conversion u-joint or switch driveshafts, but it seems like my stock driveshaft already is 1350. All the bearing caps measure out at 1.19 (1 3/16") dia, which is the size of a 1350, and the yokes on the 8.5 and 9.5 are identical. So it seems I could have left my old u-joint in there, but new Spicer on order now. Can't hurt to have a new rear u-joint. Just trying to figure out why some have had to do a conversion and I don't. Maybe they changed the size in the later years of GMT 900? Mine's a '13.

getting the correct u-joint size is tricky at best for our trucks, I looked into it one time and ended up having to guess and I probably have the wrong sized ones still sitting in my tool box from 7 years ago. Best bet is to get the part number from a dealer based on your vin number.

 

[swathdiver]

getting the correct u-joint size is tricky at best for our trucks, I looked into it one time and ended up having to guess and I probably have the wrong sized ones still sitting in my tool box from 7 years ago. Best bet is to get the part number from a dealer based on your vin number.

The current GM number is 89059111. The original AAM number is 19256728. The Spicer 1355 is 5-1350X.

 

[Doubeleive]

The current GM number is 89059111. The original AAM number is 19256728. The Spicer 1355 is 5-1350X.

is that the same for all drivelines? aluminum, steel, 2wd, 4wd, awd, 5.3, 6.2, swb, lwb.?

 

[swathdiver]

is that the same for all drivelines? aluminum, steel, 2wd, 4wd, awd, 5.3, 6.2, swb, lwb.?

For certain it is for the 6-speed equipped SUVs and pickup trucks, whether or not they have aluminum driveshafts or steel, are 4x4s or AWD or RWD. It is not the correct joint for the 2500s, save for the 2007. After that year they went to the 1415 series. My memory is fading on this now, I did write down the VINs of the various configurations to help me remember. But I saved the spreadsheet within several files and cannot remember which was most current and where it even is!

 

[DaveO9]

The current GM number is 89059111. The original AAM number is 19256728. The Spicer 1355 is 5-1350X.

Whew, I ordered 51350X (5-1350X) from RA. (Actually ordered two, might as well do the other one on the rear driveshaft as well.) I've been nervous all day, after I read your first post about 1350 vs 1355. I wasn't sure which one I ordered (just used RA's part selector tool) and didn't know there was a difference when I ordered. And I've read two different articles - one said they were not interchangeable, another said it's fine to interchange. In any case, I think I have the right ones coming to me. thanks much for the help!

Here's the article that says they are interchangeable, for anyone interested: https://torqueking.com/product/sku/u-joint-id-spicer-1350-and-aam-1355-series-idn-142/
Plain as day, there's a sticker on my driveshaft that says it was manufactured by AAM.

 

[5StarCustmSolutns]

I reckon that as long as the brackets are straight, the control arms will fit inside them and it will track straight down the road. @iamdub @Doubeleive @gooffeyguy @randeez

What does everyone else think about those brackets and getting them straight?

May squeak a little but as long as control arms are bolted in to spec torque **AND track bar is CORRECT length, it should roll out straight. I would do my best to flex the steel back as close to OE as possible, any squeak squeak would drive me mad. But seriously, the steel (let's call them)sleeves that extend over the control arms are not that stiff, you can straighten those out w/o too much effort...
I've always used something like an XXL crescent wrench pinched as tight and deep as I could get and a cheater bar(pipe) for leverage to flex the steel slightly past it's desired location so it spring back into desired location

**just for an example of how important, or not, the rear end track is, or maybe to show how little those slight bends will affect it, and DEFINITELY to show you what not to do: --I bought a lightly used Spohn adjustable rear track bar off of the classifieds on this forum, adjusted it to the exact length of the factory bar(the bracket on my 2011 was in the identical location as the new to me 2012 14 bolt rear end), tightened the jams down and set it aside until I was ready for it.

--When installing the rear end I placed both ends on harbor freight dolly's so I could roll it L <> R and F<>R for alignment purposes

--I attached all four control arms tightening bolts to well over hand tight

--Then grabbed Spohn track bar and it was like 2" short......well w/o hesitation I lengthened it right on out there and bolted it in.

--Then the springs, shocks, and sway links. And everything bolted up just dandy

--My1st test drive was over to town to get wiper blades, on which I had forgotten to remove the c-clamps from the rubber section of the brake lines, which was a major distraction from any kind of investigative listening. 2nd test drive was fully loaded down and leaving for 3500mi 3wk road trip to Texas. I drove the first 50miles and everything seemed fine. Tracked straight when I let go of the wheel accelerated decelerated normally and did not shake.....so I drug myself most of the way into the back seat and passed out. We got 16.9mpg on the way down, only using 5 gears(TCC lock issues), and that was driving 80-90 as much as possible. I normally get 13 or 14 here in the mountains and had just gone from 3.08 to 3.42 so I was happy
--The pertinent part- EVERY TIME I walked up on my truck to get in during the trip I thought to myself "the rear tire looks different??" It took 4.5weeks and 4000+ miles of me noticing that my driver rear tire looked wider, looked different, before the lightbulb came on. I had extended the track bar almost 2" over stock length while rushing around to get the rear end installed......smh. I measured, and sure enough was about .875" cocked out to drivers side......smh. Truck drove and tracked straight, and it could not have had any major effect on mpg, but it was off. Wayyyy off vs alignment parameters

Also, I did not need u-joint adapter. Mine was already a 1350 but I bought it(and never returned it....smh)

Also, personally I would straighten out those dust shields and roll with them, they don't look that bad to me? Pretty sure mine were close to that when I got my 14bolt? Or at least were after rolling it off jackstand onto my foot.....in Crocs

And.....man I'm really ratting myself out here......I put calipers on backwards which makes it impossible to bleed correctly. I didn't think much of the softer pedal, but when I awoke my lady was going on and on about it, so we stopped in STL and I checked and derrrr, I got a wooden spoon. Make sure your bleeders are on the top

Lastly, for the front diff, obvi you need match ratio w/rear. But my truck is a selectable 2wd 4HI 4LO and I bought a 3.42 front diff from a junkyard for $100 not realizing it was off an AWD lol..... I panicked for about 30seconds then after examining my old one vs the AWD, I recognized that it was possible to swap sections of each of them and make the 3.42 a selectable while making the 3.08 an AWD for resale. Just wanted to share that In case it comes into play??

Will happily answer any questions about this, just went through it last year... And wouldn't have gotten through it without this group right here: @iamdub @Doubeleive @gooffeyguy @randeez @swathdiver @Geotrash (sorry if left anyone out)

 

[5StarCustmSolutns]

Whew, I ordered 51350X (5-1350X) from RA. (Actually ordered two, might as well do the other one on the rear driveshaft as well.) I've been nervous all day, after I read your first post about 1350 vs 1355. I wasn't sure which one I ordered (just used RA's part selector tool) and didn't know there was a difference when I ordered. And I've read two different articles - one said they were not interchangeable, another said it's fine to interchange. In any case, I think I have the right ones coming to me. thanks much for the help!

Here's the article that says they are interchangeable, for anyone interested: https://torqueking.com/product/sku/u-joint-id-spicer-1350-and-aam-1355-series-idn-142/
Plain as day, there's a sticker on my driveshaft that says it was manufactured by AAM.

hopefully reading my laundry list of mistakes can help you relax... I was a nervous wreck, mostly bc I waited to late to start before our trip and had to rush. You've already fig out not to do that so you'll be fine!

 

[swathdiver]

Whew, I ordered 51350X (5-1350X) from RA. (Actually ordered two, might as well do the other one on the rear driveshaft as well.) I've been nervous all day, after I read your first post about 1350 vs 1355. I wasn't sure which one I ordered (just used RA's part selector tool) and didn't know there was a difference when I ordered. And I've read two different articles - one said they were not interchangeable, another said it's fine to interchange. In any case, I think I have the right ones coming to me. thanks much for the help!

Here's the article that says they are interchangeable, for anyone interested: https://torqueking.com/product/sku/u-joint-id-spicer-1350-and-aam-1355-series-idn-142/
Plain as day, there's a sticker on my driveshaft that says it was manufactured by AAM.

Yes, using the right snap ring will make it work, but not all packaging includes all the different sized snap rings.

 

[DaveO9]

May squeak a little but as long as control arms are bolted in to spec torque **AND track bar is CORRECT length, it should roll out straight. I would do my best to flex the steel back as close to OE as possible, any squeak squeak would drive me mad. But seriously, the steel (let's call them)sleeves that extend over the control arms are not that stiff, you can straighten those out w/o too much effort...
I've always used something like an XXL crescent wrench pinched as tight and deep as I could get and a cheater bar(pipe) for leverage to flex the steel slightly past it's desired location so it spring back into desired location

**just for an example of how important, or not, the rear end track is, or maybe to show how little those slight bends will affect it, and DEFINITELY to show you what not to do: --I bought a lightly used Spohn adjustable rear track bar off of the classifieds on this forum, adjusted it to the exact length of the factory bar(the bracket on my 2011 was in the identical location as the new to me 2012 14 bolt rear end), tightened the jams down and set it aside until I was ready for it.

--When installing the rear end I placed both ends on harbor freight dolly's so I could roll it L <> R and F<>R for alignment purposes

--I attached all four control arms tightening bolts to well over hand tight

--Then grabbed Spohn track bar and it was like 2" short......well w/o hesitation I lengthened it right on out there and bolted it in.

--Then the springs, shocks, and sway links. And everything bolted up just dandy

--My1st test drive was over to town to get wiper blades, on which I had forgotten to remove the c-clamps from the rubber section of the brake lines, which was a major distraction from any kind of investigative listening. 2nd test drive was fully loaded down and leaving for 3500mi 3wk road trip to Texas. I drove the first 50miles and everything seemed fine. Tracked straight when I let go of the wheel accelerated decelerated normally and did not shake.....so I drug myself most of the way into the back seat and passed out. We got 16.9mpg on the way down, only using 5 gears(TCC lock issues), and that was driving 80-90 as much as possible. I normally get 13 or 14 here in the mountains and had just gone from 3.08 to 3.42 so I was happy
--The pertinent part- EVERY TIME I walked up on my truck to get in during the trip I thought to myself "the rear tire looks different??" It took 4.5weeks and 4000+ miles of me noticing that my driver rear tire looked wider, looked different, before the lightbulb came on. I had extended the track bar almost 2" over stock length while rushing around to get the rear end installed......smh. I measured, and sure enough was about .875" cocked out to drivers side......smh. Truck drove and tracked straight, and it could not have had any major effect on mpg, but it was off. Wayyyy off vs alignment parameters

Also, I did not need u-joint adapter. Mine was already a 1350 but I bought it(and never returned it....smh)

Also, personally I would straighten out those dust shields and roll with them, they don't look that bad to me? Pretty sure mine were close to that when I got my 14bolt? Or at least were after rolling it off jackstand onto my foot.....in Crocs

And.....man I'm really ratting myself out here......I put calipers on backwards which makes it impossible to bleed correctly. I didn't think much of the softer pedal, but when I awoke my lady was going on and on about it, so we stopped in STL and I checked and derrrr, I got a wooden spoon. Make sure your bleeders are on the top

Lastly, for the front diff, obvi you need match ratio w/rear. But my truck is a selectable 2wd 4HI 4LO and I bought a 3.42 front diff from a junkyard for $100 not realizing it was off an AWD lol..... I panicked for about 30seconds then after examining my old one vs the AWD, I recognized that it was possible to swap sections of each of them and make the 3.42 a selectable while making the 3.08 an AWD for resale. Just wanted to share that In case it comes into play??

Will happily answer any questions about this, just went through it last year... And wouldn't have gotten through it without this group right here: @iamdub @Doubeleive @gooffeyguy @randeez @swathdiver @Geotrash (sorry if left anyone out)

Thanks for all your thoughts and advice. I've already started the return with LKQ for the rear end. If it were just the track bar bracket and the control arm bracket I would probably straighten as best I can, but then later I discovered that the PS flange where the dust shields/p-brake mount to, one corner is definitely tweaked. It's hard to see in pics so I didn't post, but the bolt in that corner definitely skews outward. I'm uncomfortable with what that would do to the mounting surface for dust shield, and for it to bend that 3/8" plate it seems like it was hit hard there. I originally thought this thing fell off a fork lift, but now I'm wondering if the donor was totaled from behind or rear pass side. With all three damaged areas, I think it's just too risky and worth the extra hassle of having to go through LKQ's return process. (PRO TIP: don't do what I do and buy from LKQ Online/National sales. Call the one close by and work with local sales folks, even if they don't have what you're looking for. They'll charge you the $50 transfer fee just like the national will do. And returns much easier if you work with local)

EDIT: I found out later that ordering from the local branch of LKQ incurs a core charge, whereas the online part of the business does not do core charges, and the slightly lower prices from ordering locally do not make up for that core charge. So if you are upgrading, like 8.5 to 9.5 rear end, you may not want to order locally)

Regarding the dinged up dust shields, kind of immaterial now, but I'm cheating and just using my OEM ones - I haven't even detached the parking brake cables from them. Amazing that you can get the whole rear out without breaking any brake lines or disconnecting p-brake cables. And same with brakes... no bleeding required, the entire brake line assembly is fully intact and zip tied to the frame. No connections broken and my existing lines look to be in great shape.

On the front, you may be answering a question I have. Here are the four options available when I search LKQ:

The front that I just took out has a sticker identifying it as a AABT. So I'm making an assumption that I want the AABR 3.42 option, since the code is so similar to the one I'm replacing. But I'm not 100% sure on that. If anyone has any clarifications, please chime in.

Thanks again, appreciate the support on the swap and hearing from another person that went through it. And thanks for further confirmation on the u-joint issue!