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A555 A520 OBX Hybrid Transmission Build Tips

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20K views 21 replies 5 participants last post by  The Pope 
#1 · (Edited)
A555/A520/OBX Tranny build tips

I am building my first A555/A520/OBX hybrid transmission. This unit is an A555/A520 hybrid with an OBX LSD installed. You cant get the OBX for the A555 directly, but you can swap in an A520 intermediate shaft and ring gear and get the OBX in an A555...and that is what we are doing here.

I have been building engines for years, but this is my first manual tranny. Since this is my first tranny rebuild, I am wet behind the ears, a green horn, Im sure to make a small mistake or overlook something that an experienced eye might have not missed so I thought I would just ask:

What are some of the common mistakes made when rebuilding a tranny?
What do I need to be sure to do or not do?
How do I determine if a synchro is worn (out) by visually inspecting it?
Assembly tips, etc.

I have everything needed. Two same year trannys, an A520 and an A555, a complete set of bearings, seals, and synchros for this unit. It's the late model 89 style A555 with the large nut on the end of the intermediate shaft rather than the c-clip.
 
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#2 ·
re: A520 A555 OBX LSD Build Instructions & Tips

check the steel plate everyone recomends changeing out for the moly plate , it can wear thin around the holes the shafts pass through

next check the alum plate that goes next to it - look for a crack between the holes the shafts pass through

I found the best way to keep track of the parts that come off the secondary shaft is to stack them on the bench , first part off , on the bottom of the stack - next one on top of it etc

you'll need to find the tools to bang out/ off the old bearing races and cups & to bang the new ones in -- or find a nice trans guy to do it for lunch money (easiest way)
once the bearings are delt with the trans it's self is relitavely easy - though I've noticed that getting the guts out & into a 555 seems tougher than the old 525's
 
#4 ·
Re: A555/A520/OBX Build Tips

Here is why you replace the end plate with a new OEM one or a better and stronger chrome-molly replacement unit. Under hi-boost and/or spirited driving, this plate actually flexes outward and over time it will not snap all the way back flat again. This flexing action wears a groove in the plate as well and the bearings loose their critical pre-load and will simply just come apart after the components start to exit their respective cages and races due to the additional clearance.

The last picture is of a new chrome-molly end plate.
 

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#5 · (Edited)
Re: A555/A520/OBX LSD Build Tips

Here is a shot of the A555 and A520 ring gear next to the OBX LSD. You can see why the OBX wont fit the larger solid 555 gear, the gear is solid and you physically can't bolt the OBX to it.

But to get the 3.50FD I wanted in the tranny(the 555 was a 3.87), you take the 520 intermediate shaft and ring gear and combine them with the gear set and case of an A555. If you look close you can tell the pinion of the 520 shaft is a bit larger than the 555 unit and the ring gear has 1 tooth less or more depending on which ring gear you are holding. Both pinions have the same number of teeth but the ring gears are 49 and 50 tooth.
 

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#6 · (Edited)
Re: A555/A520/OBX LSD Build Tips

To build the 520/555/OBX hybrid you basically need to acquire two same year trannys, one A555 and one A520. There was a change in 89 with the intermediate shafts being different between the years so get either two 89s or two 87-88s.

These pictured are 89 units. You can tell them apart by noticing the large nut on the end of the input shaft on the A520 input shaft.

The picture reveals also the differences in the non-getrag gears of the A520. The A555 uses the heavy duty new process Getrag gear set.

Look even closer and you might notice the end of the A555 shaft starting to chip just a bit, this is the first sign of wear on these. The A520 unit shows no pitting at all yet, just normal discoloration.

So to build this hybrid, you use the A520 intermediate shaft and ring gear, everything else comes from the A555..except the OBX LSD that is.
 

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#7 · (Edited)
Re: A555/A520/OBX LSD Build Tips

Here are a couple of shots of the ends of the intermediate shafts. You can see the wear on both of them. Both units are still usable however. "turbovanman" is said to have/has the ability to recondition the shaft surface back to o.e spec and size and hardness...however I do not have any personal experience with that service. I would like to know what that might cost and post here for others to see.
 

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#8 ·
Re: A555/A520/OBX Build Tips

Here are a couple of shots of the OBX unit. The finishing of the OBX unit varies greatly so I suggest that you opt-in to have your supplier perform this service for you if you are not familiar with these units. A typical raw OBX unit will often need to have threads chased with a tap and casting flash removed. Also suggested is to replace the fastener hardware with higher grade bolts. I was fortunate enough to get Chris from TurboUnleashed to prep my unit for me. Its an affordable service that will save me countless hours of kicking myself in the back side for not doing it right the first time!
 

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#9 · (Edited)
Re: A555/A520/OBX LSD Build Tips

The large sealed bearing goes on the end of the intermediate shaft and must be pressed on or off. In some rebuild sets, this bearing is shipped w/a compatible (pronounced cheaper!) bearing.

The other end of the intermediate shaft goes into the inner bearing race which is pressed into the front of the tranny case. You can see it in the picture below with the small retaining strap still holding it in place. Story goes its not good to mix and match intermediate shafts and bearings. The shaft is not available new and when it was, it shipped with a new bearing. You can replace the bearing still and you should.
 

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#10 ·
re: A520 A555 OBX LSD Build Instructions & Tips

ehh, not totally true with that last statement. i've bought many intermediate shafts when they were available, none of them came with a new bearing, you had to buy that seperately. also if the case hardening is damaged at all on either of those intermediate shafts, that will need to be repaired before using them or they will undercut and tear up the gearsets (something you dont wanna have happen) turbovanman has the ability to recondition the shaft surface back to o.e spec and size and hardness.
 
#11 ·
re: A520 A555 OBX LSD Build Instructions & Tips

Here is a portion of the complete rebuild kit that I purchased. Paid about $300. Pretty much everything I needed was in the kit except for the small parts kit which would have included the snap rings and a few other small items. This kit was spose' to be for an 89 unit....its an 87-88 unit I can tell because SOME of the synchros in the 89 unit are not single piece as shown in this kit. They are multi piece. I was lucky, I have two used but good sets of the multi-piece style synchros. Included in my kit were bearings for the intermediate and input shaft, differential bearings, all seals, shift fork pads.
 

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#12 · (Edited)
After installing the new OBX LSD in the diff housing, an initial guaging shim is installed in the diff bearing end retainer and the entire assembly bolted together. Pictured here is the dial indicator set at 0* just before pushing up on the ring gear to measure the amount of deflection/end-play. I had 17/1000 of an in" of total end-play, so I added the suggested preload amounts of 6-10/1000 for a total additional shim thickness need of 23-27/1000 of an inch. The shim package I purchased was a pack of 10 shims, each .005in think. 5 x .005 gave me .025in total shim which was perfect. You have to take it all apart again to install the final shims by the way. I found the Diff shims needed at: www.transmissionpartsusa.com

Also pictured with the coins are the ring gear bolt (12 required) and the smaller shim for the input shaft bearing. These also come in a variety of thicknesses.

Here is a link to a two minute YouTube on how to use a dial indicator, its worth the watch even if you've already used one.
Reading and Using a Dial Indicator.mp4 - YouTube
 

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#13 ·
So here is the whole shebang all assembled and cleaned up. I plan to fill it with RedLine MTL and it will be driven by a TurbosUnleashed Yellow plate and 6 puck thanks to Chris over there. Also got one of their lightened steel flywheels and the ARP fasteners for the flywheel to crank as well as the clutch pressure plate to flywheel thanks to Cindy over at FWDPerf.

I opted to wrinkle finish the end cover, I think it adds a nice touch. This unit is going in my DD GLHS L-Body so I am also doing the heim shifter joint upgrade at the same time as building the two custom linkage brackets so I get to keep the rod-shifted set-up with the later A-555/520/OBX LSD tranny.

To make the larger of the two brackets I just cut the OEM A555/520 bobble strut bracket just right and welded it to the standard A525 bracket so that all the linkage, as far as the tranny goes is right where it was before. I works perfectly and is OEM strength I guess. The other bracket is just a thick piece of angle iron two holes and the OEM pivot pin welded to it.

I have pictured the larger bracket with a front, back and side shot to help you see how that is done. This works great on L-body cars to install the A555/520 and keep your dogbone torque rod. You can also use the poly/solid adjustable dogbone now as well.
 

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#14 ·
Here is the pressure plate, disk and flywheel combination I decided to go with. All this custom stuff came from Chris at TurbosUnleashed. The lightened steel flywheel seemed to be an excellent compromise in cost and streetable performance for my daily driver needs. The yellow clutch should give me ample clamp for my 250/275 HP target and the 6 puck is reported to be kind and tame enough for the street with enough bite to not be chattery at the same time. Not very tollerent of fluids I hearing though so a good fresh rear main seal is also installed, I went w/the full teflon type on this one.
 

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#15 ·
To use the A555/520 in an l-body you need the larger size axels so to get that all you have to do is buy 90+ Omni automatic axels and stuff them in your A555/A520 5 speed diff! Perfect fit and OEM. Pictured are the automatic axels inserted in the 5 speed. Also it's easy to tell the size difference in the third picture.
 

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#16 · (Edited by Moderator)
where did you find the shims for the diff ? I wound up using some leftover adjustable pinion shims from a rear end that had machined out the centers a bit but they worked perfectly once that was done, ive got 30k on my hybrid 555 its a stout transmission to be sure. I would recommend at least taking apart the unit and cleaning deburring it and making sure everything is torqued properly, lots of flash and rough machining in there plus the area where the axles go in to the splines needs to be opened up a tad to allow the axles to fit properly, one side on mine was tight and required a couple of passes from a brake hone to get the axle to come in and out fairly easily and the other side was ok...

Another tip id like to add to the rebuilding of the trans, take pics of the gear sets before anything is broken down, it will make life much easier.
 
#17 · (Edited by Moderator)
The Diff shims are made by Sonnax,
Part#: 39539-Z5 <$10
I sourced them from: Transmission parts USA Automatic transmission parts

The rebuild kits:
57.3mm O.D. front pinion bearing1st and 2nd synchro rings are single piece design
DTSBK375WS (w/synchros)$300+ DTSBK375 w/o synchros $150

57.3mm O.D. front pinion bearing1st and 2nd synchro rings are multi-piece design DTSBK375AWS (w/synchros) $300+ DTSBK375 w/o synchros $150

I sourced them from: Ring and Pinion, Transmission and Transfer Case Parts - Drivetrain.com (NOTE: THE KITS THAT COME W/SYNCHROS ARE MORE EXPENSIVE THAN DISPLAYED ON THE NET. YOU CAN ORDER AT THE DISPLAYED PRICE BUT HE WILL CALL YOU TO COLLECT A TOTAL OF $300 OR MORE)

IF the synchros are apparently good, skip them and the added cost and save $150.
 
#19 ·
I am adding that FWDperformance.com has the OBX, the washer kit and the chrome retainer plate.

I found replacing the bolts and washers is a piece of cake, not something to pay for lol. Now all we need is the info on doing this to my 568 lol
 
#20 ·
doing this job on my sons car, forgot the end play. But the range you are looking for is .006"-.012" of end play on your differential bearings. That is the number you want to end with anyway on the dial indicator.
 
#21 ·
Yes, the end play is REALLY important to how noisy the diff is after assembly and when put in service. My experience is that you really do want the bearing to have a preload ( a -/1000 clearance) or it will have a tendancy to whine down the highway in 5th gear. So when I set my last one up, IIRC, I assembeld the diff with the spacing shim and measured end play, for example it might have been 6/1000 of an inch. I then disassembled the carrier with the shims in it and added enough shims to have something like -5/1000 preload, meaning I had to add 11/1000" of shims.
 
#22 ·
You should have 6-12 thou in end play. At 6 though you are on the edge of tight though.

The problem I find is forum import kids and how they did it. So you get people following bad advice. My son just did the swap and listened to Honda kids, stupid. He added it with an impact wrench and new bearings, no end play or shims. Well they all slap it in he says lol.

For clarity we bought new Timken bearings, not imported garbage. Actually pretty cheap like $20 for 2 bearings.

Get the Sonnax kit for shims.

Press the bearings on without shims and put it in the trans with end cups and no outer cover. Important, set the trans so the diff is vertical.

Using screw drivers and the end play gauge, lift the diff and measure end play.

Do the math and stack the .005 shims to get into the .006 to .012 range.

My sons car had no end play the way he put it in. He didn't get the bearings seated and was going to drive it lol. Then seated with new bearings it was .040. So he added .030 shims to get to .010 end play.

Look at the ring gear and add shims to the side that centers the ring on the pinion gear best.

Always add the new Belleville washers.

In the end with shims, bearings, washers, etc you are still around $500 and the mod is actually pretty easy. EVERY turbo Dodge should have had these stock so even if you want to keep yours stock but drive it, add the posi lol.

My trans is a bit more tough, need to figure out a 568 rebuild kit. Then I can get my hybrid done.

My sons setup is your best bang for the buck easy.

UFC Stage 3 Clutch Kit Chrysler Dodge Daytona LeBaron Shadow Sufcrit 2 5L Turbo | eBay

The diaphragm is 50% thicker for more PP pressure. They use 4 stock PP guide straps, vs 1 a piece. I just lost a T3/T2 clutch with a Sachs PP by snapping these. Then a really nice 4 puck disk with stronger springs. Really nice clutch for the money but requires big pilot shaft.

Then he got a 93, 3.77 geared 523 and the cables.

Then a SRT 4 short shifter off Ebay cheap and poly shifter bushings.

About $750 for all of it, get combo.
 
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