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Rovan teardown pt1 rear diff /suspension blueprint

Polar_Bus

Well-Known Member
Messages
168
Location
New Hampshire USA
So if your not familiar with the term "blueprint" it's simply a term used to describe a precision measurement / fitment and assembly of parts or assemblies. Checking all components and identifying potential trouble spots from poor "china" based tolerances.
Now that I have my new Rovan RTR disassembled completely down to the chassis (including stripping the engine down to a long block, it's time to start removing some "slop". Some issues I can correct, others they are what they are. The idea for reliability is to remove unwanted chassis flex, without adding too much rigidity so as to have a small amount of "forgiveness flex" when crashing hard. The Rovan is overall nicely engineered IMO, the front end is tied in nicely and except for the fact the rear upper A arm mount is independently unsupported is my only concern. I'll create a separate post for that mod. The rear is another story. I have concerns about the fact that the rear engine and bulkhead is a separate pan chassis that's not really tied in to the rear bulkhead all that well. It's good, but not great IMO. This thread i'll just go over my mods for the rear trans assembly and suspension.

Mod #1 was disassembly of the trans and lube all the bearings with Mobil 1 syn grease. Rovan from the factory has almost NO grease in the bearings, and it's garbage crack jelly grease. I opened up my diff and to my surprise the diff spider gear clearances are good, no need for shimming. Added 10K silicone diff oil. Added some Mobil 1 grease to the internal metal trans gears (again some type of crappy blue grease from the factory and a TINY amount in the case. Trans gear rotation feels very smooth and precise.

Mod #2 was the typical adding washers to the upper heim joint. I like adding a bottom washer to add some support to where the ball mounts to the plastic hub. I also add a large washer to the top as a safety thing so I don't have a joint pop and loose total steering control. Cheap insurance.

Mod #3 was to shim the control arms. From the factory they are not too bad, but there was definitely room for improvement. I shimmed the arms to almost zero side / side play using Fasteddy shims and they operate very smooth.


Mod #4 was adding longer bolts to the upper shock mount. Both my lower lower bracket bolts were stripped out from the factory. I added longer hex bolts and drilled to holes completely through the plastic shock brackets. Did the same for the upper bolts as well I had some longer socket head bolts for the upper bolts. I like adding washers where bolts mount to aluminum for better support and you don't gall up the aluminum from tightening the bolts.

Lastly removed all the axle boots and added some Mobil 1 grease.

Been working the rear assembly for the past few days, big job with a few issues but in the end this assembly is tight and true. Should perform perfect and run reliable !



 
Last edited:

Z.hb71

Well-Known Member
Messages
3,780
Location
Manvel, Texas
So if your not familiar with the term "blueprint" it's simply a term used to describe a precision measurement / fitment and assembly of parts or assemblies. Checking all components and identifying potential trouble spots from poor "china" based tolerances.
Now that I have my new Rovan RTR disassembled completely down to the chassis (including stripping the engine down to a long block, it's time to start removing some "slop". Some issues I can correct, others they are what they are. The idea for reliability is to remove unwanted chassis flex, without adding too much rigidity so as to have a small amount of "forgiveness flex" when crashing hard. The Rovan is overall nicely engineered IMO, the front end is tied in nicely and except for the fact the rear upper A arm mount is independently unsupported is my only concern. I'll create a separate post for that mod. The rear is another story. I have concerns about the fact that the rear engine and bulkhead is a separate pan chassis that's not really tied in to the rear bulkhead all that well. It's good, but not great IMO. This thread i'll just go over my mods for the rear trans assembly and suspension.

Mod #1 was disassembly of the trans and lube all the bearings with Mobil 1 syn grease. Rovan from the factory has almost NO grease in the bearings, and it's garbage crack jelly grease. I opened up my diff and to my surprise the diff spider gear clearances are good, no need for shimming. Added 10K silicone diff oil. Added some Mobil 1 grease to the internal metal trans gears (again some type of crappy blue grease from the factory and a TINY amount in the case. Trans gear rotation feels very smooth and precise.

Mod #2 was the typical adding washers to the upper heim joint. I like adding a bottom washer to add some support to where the ball mounts to the plastic hub. I also add a large washer to the top as a safety thing so I don't have a joint pop and loose total steering control. Cheap insurance.

Mod #3 was to shim the control arms. From the factory they are not too bad, but there was definitely room for improvement. I shimmed the arms to almost zero side / side play using Fasteddy shims and they operate very smooth.

Mod #4 was shimming the steering rack. My rack had a lot of vertical slop which will cause wobbly erratic steering. I was able to use the Fasteddy hub/clutch shims on the tops and bottoms of the steering posts and again removed all the unwanted play and gained a nice precise steering pivot action.

Mod #5 was adding longer bolts to the upper shock mount. Both my lower lower bracket bolts were stripped out from the factory. I added longer hex bolts and drilled to holes completely through the plastic shock brackets. Did the same for the upper bolts as well I had some longer socket head bolts for the upper bolts. I like adding washers where bolts mount to aluminum for better support and you don't gall up the aluminum from tightening the bolts.

Lastly removed all the axle boots and added some Mobil 1 grease.

Been working the rear assembly for the past few days, big job with a few issues but in the end this assembly is tight and true. Should perform perfect and run reliable !

Well this is cool. I need to do this to my Baja, mone is all over the place. The arms are loose and have a ton of play and slop. Need to fix my sh!t 😂
 

Polar_Bus

Well-Known Member
Messages
168
Location
New Hampshire USA
This is going to be a multi step build that I think will be helpful to the guys buying Rovan RTR's. It will give the newer guys a baseline of info to help with the learning process and how to make these cars reliable. Rather than lump all my mods and progress into one giant thread i'll break things up into parts so guys can read and learn on only the component that they are interested in.
 

Z.hb71

Well-Known Member
Messages
3,780
Location
Manvel, Texas
This is going to be a multi step build that I think will be helpful to the guys buying Rovan RTR's. It will give the newer guys a baseline of info to help with the learning process and how to make these cars reliable. Rather than lump all my mods and progress into one giant thread i'll break things up into parts so guys can read and learn on only the component that they are interested in.
good idea. Hell this will help even me, my Baja is all out of wack like I said so when the time comes, I'll follow all your shimming and stuff 👍
 

Seandonato73

Well-Known Member
Messages
1,217
You should see my dbxl steering slop... lol. It's about comical. I never thought of shiming the end play out of it. It's a really good idea polar!
 

Polar_Bus

Well-Known Member
Messages
168
Location
New Hampshire USA
Seandonato73, I'll do a "front end" blueprint in another thread, I actually got too far ahead of myself and added some steering comments into this thread. I deleted them, and i'll detail with pics how to do the steering shimming. Makes a big difference in the overall steering linkage precision.
 
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