Guidance on rebuilding 308 Seat Rails | FerrariChat

Guidance on rebuilding 308 Seat Rails

Discussion in '308/328' started by TurtleFarmer, Mar 10, 2020.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    My driver side seat rails need to be rebuild. The adjuster rail only has three bearings left in it and a single roller (I think), and the non-adjustable rail has zero bearings and no rollers.

    The simplest would be to buy new ones. But after calling the usual suspects, it would appear that these rails are rare. Really rare.

    I've looked thru the forums and have only found one thread that describes a rebuild for a Mondial:
    https://www.ferrarichat.com/forum/threads/mondial-qv-seat-rail-fix.482074/

    Does someone have pictures or a diagram of a teardown of the 308 rails? They are definitely diff't from the Mondial, and that thread doesn't really go into enough detail on the assembly of the pieces. I need to understand things like # of bearings in each rail, which side of the detent they go on, where the rollers go, etc. My passenger side seems to be intact--so I could use that as a pattern. But I'm hoping someone has already done this type of work and can provide some guidance.

    Thanks!
     
  2. Ferraridoc

    Ferraridoc F1 World Champ
    Owner Silver Subscribed

    Jun 20, 2012
    16,057
    Gold Coast, Aust.
    Full Name:
    Patrick
    I rebuilt my 400i ones, and I think they're the same. The rail with the adjuster on it is just a slider - simple! It may have rollers, but I don't remember. The other side is... difficult. There are 2 cylindrical rollers, and 48 7mm ball bearings. Mine had one roller and four ball bearings when I started, and it took a while to figure it all out. The rail is two opposed U channels with the rollers in between the flat top and bottom, and the ball bearings sitting in a space created by opposed convex recesses in the vertical walls. They are trapped by two roll pins at each end. When you pull it apart, you will notice a dimple in the middle of the flat section, which limits the roller travel, so one stays front, and one stays at the back. The rollers are steel with a rubber ring the sits in a little recess - so the roller is a bit like a cotton reel. I cut down a socket from a $2 socket set that was the right size - I think I jammed it into a small piece of plastic hose to give it some cushioning, but I could not recreate the roller perfectly - lots of trial and error to get it right. You need the patience of a saint, the ability to laugh as grease gets everywhere, and the assistance of an intelligent octopus to put it back together. Have fun!
     
  3. Alex308qv

    Alex308qv Formula Junior

    Jul 1, 2016
    378
    PA
    Full Name:
    Alex
    Did you try Russ at FerrParts for salvage ones?
     
  4. Nuvolari

    Nuvolari F1 Veteran
    Owner Silver Subscribed

    Sep 3, 2002
    6,370
    Toronto / SoCal
    Full Name:
    Rob C.
  5. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    Thanks to @Nuvolari and @Ferraridoc for links/guidance. Also to answer @Alex308qv : yup, Russ was my first call and nope, he had no rails.

    So I put together a quick writeup on my "rebuild" in hopes it helps someone down the road. A few notes before I begin, tho. The intention of the rebuild was to make functional but not to invest a ton of time and $$ into restoring the rails. My goals for my 308 are to have fun with it: keep it running and drive it a lot. It has a ton of miles, what looks to be a rattle can paint job and duct tape on the seats. Mechanically and electrically, it should never let me down. But it won't ever win a beauty contest. So "rebuild" might be an overstatement--I wanted to fix the seat rails so that they were functional and safe.

    Also, my apologies for not having more pictures. I'd intended to take a ton throughout the process...and then didn't. Sorry.

    So the symptom of my seat rails when I started: The seat rocked back and forth just by shifting weight (about 8-10deg). Either by rocking back or "lifting" the seat up, the position lock would disengage and the seat would move front to back freely. This had the added benefit of hard braking events sometimes causing the seat to move backwards as you engaged the pedal--basically making it difficult to keep pressure on the pedal. Fun!

    After removing the seat from vehicle (very easy...four nylock nuts accessed from bottom of vehicle), I tried to remove the rails from the seat. The front bolts removed easy, but the rear bolts (shallow 6mm heads) were very difficult. Soaking for 1.5 days in Kroil + a bit of heat (be careful of the leather!!!) still didn't budge--and you need to be super careful not to strip those heads. Eventually I was able to remove the adjusting rail with a hand impact tool (these are great!), but the non-adjusting rail simply didn't want to come off. I could have drilled it out, but didn't want to risk damage to the seat threads and chose instead to try to fix the whole assembly with the bottom half of the rail remaining attached to the seat. I was easily able to remove the portion of the rail that wasn't attached to the seat (the piece that attaches to the floorboard).
    Image Unavailable, Please Login Image Unavailable, Please Login
     
  6. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    As found, both rails were missing a lot of pieces. The adjuster rail had a single roller, and 3 bearings and 1 bearing on the front half. The non-adjuster rail had no roller and no bearings. Additionally, the adjuster bar retaining pieces were badly bent out of shape such that the bar itself was at an odd angle. The adjuster rail was also slightly bowed in the middle and the piece that wasn't attached to the seat was slightly "flared" out at one end.
    Image Unavailable, Please Login Image Unavailable, Please Login
     
  7. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
  8. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    So, based on other accounts (@Ferraridoc & @Nuvolari in particular), as well as viewing the skid marks on the rails, here is what I surmise is supposed to be in there:
    Adjuster rail - two rollers (one front and one rear) and 48 bearings.
    Non-adjuster rail - two rollers (one front and one rear) and 48 bearings.
    Image Unavailable, Please Login
     
  9. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    As noted above, there was only one roller and I needed four. Thankfully, I did find one roller rattling around in the footwell (as well as a few bearings). It's a pretty simply piece and could easily be turned on a lathe. The rubber o-ring in the middle can be replaced with https://www.mcmaster.com/nav/enter.asp?partnum=9452K22 and I did put new rings on both of the original rollers (even tho the old ones were still in good shape). However, I decided that rather than waiting two or three days to get to the shop to turn new rollers, I'd just try to run w/o the rollers on the adjuster rail. I put both rollers into the non-adjuster side.

    Also, the bearings were all replaced with 1/4" hardened stainless (https://www.mcmaster.com/nav/enter.asp?partnum=9529K15). I'd originally thought these should be metric. However, a caliper on all of the "original" bearings yielded 1/4" to a very tight tolerance. The 6mm and 7mm bearings would have been either too small or too large. Of course, it's possible that these weren't the original bearings--but it seems that the quarter inch bearings worked fine.

    So, on each end of the rails, there's a little tab that needs to be bent up in order to remove the bearings (see above picture). I didn't need to do that for the non-adjusting side (no bearings) but had to for the other side. Clearly, these need to be bent out in order to put bearings back in. I'd highly recommend putting a little heat into the steel before bending--years of action can make that metal a bit brittle and you risk snapping one of those tabs off. Which I did. Grr. I was able to take a small hacksaw blade and use a bit more of the metal rail into a "tab" (otherwise my shiny new bearings would all fall out). But it still sucks and I had to be careful not to interfere with the action of the rail.

    Also, I had to address the bending of the rails and the adjuster bar retainer. This was done the old fashioned way--clamp it to the bench, gently hammer them back into place. The adjuster rail retainers took a lot of trial-and-error. It needs to engage the "teeth" on the adjuster rail, but you don't want it to bind. The bowing in the rail itself was fixed by cantilevering each half of the rail over the bench, where the bow started clamping to the bench and clamping a cheater bar to the cantilevered section. Again, gentle persuasion eventually got both halves back in alignment (they had to be done separately). The flaring of one end of half of one of the rails was fixed by slowing compressing in a vise.
     
  10. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    Before putting things together, everything received a clean bath in penetrating oil (Kroil is IMHO the best). I could have sent to the bead blaster and re-machined the bearing races and blackened it all--but again, my goal was functionality. Once cleaned up, a healthy layer of white lithium grease was applied to the roller areas and the bearing races.

    The non-adjusting side had to be put back together on the seat itself, as mentioned above, I couldn't remove it from the seat. That wasn't so bad. However, getting everything to go back in was moderately painful. Rollers went in first--one in the front and one in the back. There are four dimples in the rail that keep each roller in it's own area. It takes some trial and error--as you slide the top half of the rail over the roller it tends to want to migrate over those dimples and into the wrong area (since there aren't any bearings in there, it's easy for the roller to go over the dimple). I found the simplest was to do a combination of "lifting" the top rail so that the roller was less likely to want to move and also pushing a steel wire (i.e. coat hanger) into one end to prevent the roller from moving. Eventually, you'll get the top and bottom halves of the rail together with the rollers in the right place. best method to check is to push the previously mentioned coat hanger in to measure how "deep" each roller was in their section. Using the coat hanger, I made sure both rollers were at about the same position in their respective areas defined by their respective dimples.

    Once rollers were in, then it was time to load the bearings. These have to be fed in from four locations (two sides of the rail in front, two sides of the rail in back). These are a bit of a tight fit, particularly if your rail has been bent in any way. I used a long drift to gently tap them into each end. One thing you'll notice is that as you move the rail back and forth, the bearings seem to bind up on either the detente in the middle of the bearing race or on either end. I used a metal pick to slide the bearings towards the center to get them out of the way. How many bearings to put in? So @Ferraridoc mentions that there should be 48 total (assume 12 per "section"). I got a bit nervous about so many bearings binding up on those detentes--so I only put in 36 (9 per "section"). Mechanically, those rollers should be the primary load bearing point when you're sliding on the rails. The bearings should be providing lateral support and keep the whole assembly "tight" so all the pieces don't come apart. So I felt okay just putting in 36. But you may find you want the full complement. Obviously, after all your bearings are back in, you'll need to bend those retaining tabs back in place.

    So on the adjusting rail, as mentioned above, I only had two rollers and I'd put both into the non-adjusting side. I felt that I could always go back and get new rollers machined and put them in--I wanted to try it with just the bearings. The adjusting rails were much more of a tight fit than the non-adjusting. Even without the rollers, pushing the bearings in was more difficult. This may have been because of the bowing/flaring. One other thing of note: the adjusting bar needs to be "loaded" up so that the spring is under tension before putting the two halves of the rail together. Don't load it up too much, otherwise you'll have a dickens of a time operating the lever. Just get it enough tension to hold the tooth in the groove without coming out on it's own. Eventually, after tapping in all the bearings, and bending the tabs back, the adjusting side was ready to go.
     
  11. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    Everything went back in as it came out. The seat slides *really* well now. It stops when it's supposed to stop (front and rear). It adjust smoothly and cleanly. And it no longer rocks back and forth. When coronavirus quarantine ends, I might still go machine those rollers (will probably make a bunch of them if folks are interested) and put them into the adjuster rail, but I might also just enjoy driving the car for a while without worrying about every braking event sending me to the back of the cabin....
     
  12. Ferraridoc

    Ferraridoc F1 World Champ
    Owner Silver Subscribed

    Jun 20, 2012
    16,057
    Gold Coast, Aust.
    Full Name:
    Patrick
    That's great, Jason. I think the 400i rails are slightly different, so maybe less ball bearings is better in your case. The 400i ones are trapped by roll pins at each end and are free to move the entire length of the rail. Well done, anyway! It's always satisfying to figure out how it all works and then nut out a solution.
     
  13. Nuvolari

    Nuvolari F1 Veteran
    Owner Silver Subscribed

    Sep 3, 2002
    6,370
    Toronto / SoCal
    Full Name:
    Rob C.
    I made new rollers using an appropriate sized drill bit shank cut with an angle grinder. Works perfect and is just the right hardness. Sometimes the cheap low tech solutions work best.
     
    BigTex likes this.
  14. francisn

    francisn Formula 3

    Apr 18, 2004
    1,938
    Berks, UK
    Full Name:
    francis newman
    Great tutorial TurtleFarmer. I have just had the driver seat on my GT4 repaired - the tubular frame had sheared in 3 places which needed welding and when it came back the non adjusting rail was in bits. Both rollers there but only two ball bearings.
    I really couldn't have worked out how to do it without your help. Anyway, now all back together, the heating of the retaining indents to adjust them was a really good tip.

    However although I am happy that it now all works, I only ever have the seat fully back, I used various different size ball bearings on either side and end from 1/4 inch to 5.5mm, so I didn't do a perfect job. But it works!
    Thanks for your help-
     
  15. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    @francisn So glad it was helpful!

    I still have on my long term to-do list to machine a few of the rollers, since I put one of my rails back together w/o them. But as you said, my seats *rarely* move, so it's pretty low on my list.

    It's nice to be in a seat that doesn't wobble or slide every time you brake or take a corner. It's also nice to not have your poor passenger feel unsettled as a result of a wobbly seat--better to have them feel unsettled b/c of your reckless driving.
     
  16. francisn

    francisn Formula 3

    Apr 18, 2004
    1,938
    Berks, UK
    Full Name:
    francis newman
    Thanks Jason. We have different terminology for tools. I have used a hollow nosed punch to insert the ball bearings into the slot. Tapped with a hammer. Once past the indent the move freely.
     
  17. TurtleFarmer

    TurtleFarmer Karting
    Silver Subscribed

    Jan 13, 2020
    215
    Full Name:
    Jason S
    I think I have a set of box spanners next to my box wrenches somewhere....
     
  18. oelboxer

    oelboxer Karting
    Silver Subscribed

    Apr 4, 2018
    117
    Full Name:
    Matt Wright
    Great photos, and this mirrors my experience with the rails on my '75 308 GT4. Not enough rollers, missing bearings, and a very bent mounting tab for the adjuster arm. Thankfully, this is all pretty easy to rememdy, and as long as another giant gorilla doesn't try to adjust my seat, should be good for a lifetime.
    - Matt
     

Share This Page