New member here, and first post! Many thanks to all the contributors and admin folks for this site for making this resource available.

My 1993 W250 is giving me some rear suspension grief. It has a "discontinued" dual airbag kelderman system. I enjoy troubleshooting this stuff but am hoping to get insight from anyone with the same air setup. That said, any advice/input is also welcome.

My problem is a terrible shudder/vibration in the drivetrain under acceleration. So far I think I'm experiencing severe axle wrap because of how this dual bag system is designed. For anyone unfamiliar with this dual bag kelderman setup it makes the truck ride great, however it allows the rearward eye of the leaf spring to travel up or down as the airbag compresses or expands. From the drivers seat i feel two things during hard acceleration: 1) the rear of the truck rises up 2, 3 or 4 inches , and 2) a bad vibration. Bag psi has an affect on how easily the rear of the truck rises during accel but it never eliminates it, even at 10psi or less.

Picture attached is not of my truck but is the same kelderman setup. By design the bottom plate that the airbag rests on moves in the arc depicted by the red arrow. This bottom plate is attached with a vertical bracket to the rearward eye of the leaf spring. Red circle simply shows pivot point of the plate that the airbag rests on. As that bottom airbag plate moves up or down the entire rear leaf spring then pivots off the front spring shackle,... a constant pinion angle change!!!! I can even feel the rear of the truck rise with 1500-2000#'s of weight on the gooseneck ball when accelerating,... not as severe when compared to bobbing around for fun but still noticable that the axle wrap is happening.

My trans and Tcase are out right now. Original sachs clutch finally bit it after 280K. This truck had an nv4500 swap when i purchased it ~5 years ago. In pulling the trans i found the rear trans mount, a solid piece of square tubing instead of an actual nv4500 rubber isolator mount, completely destroyed. Cracked and ready to collapse.

In fairness to kelderman i think my pinion angle may have already been wrong. Also, the splines on my 2 piece driveshaft are very worn,...which simply amplifies any vibrations because of pinion misalignment. That said, i will be forever chasing this if I dont address how the rear leaf springs are allowed to pivot off the front shackle as a result of the axle wrap.

I'm not oppossed to ditching this bag setup and finding some stock rear leaf shackles or seeing if JungleJim is still fabbing parts. I used some of his brackets when i boxed the front frame rails and put crossover steering in a couple years ago.

I can get actual pics of my setup no problem. Sorry for the long read and hope to hear any ideas/input.
I already have a punch list of things i'm going to investigate prior to making any decision like ripping the kelderman system out of the truck. Right now i'm in research mode.

Thanks,
Paul

I

 

Welcome to the site, and I for one will be watching this thread because I'm investigating switching to a Kelderman suspension to improve the unladen ride in my C&C...You have already identified two possible culprits, namely the lack of a rubber trans mount and the worn driveshaft splines...I would correct those when you reinstall the trans, and move forward from there...The detail in the description of your problem is also a great help......Ben

 

I might consider a limiting strap of some kind. Or an anti-wrap bar that reaches further than the fwd spring eyes.

When you look at MDT air-ride, the airbag is much closer to the axle than the fwd link/spring attachment on the frame. On the Dodge, the distance from the front spring eye to the airbag and rear pivot is huge. The lever effect is multiplied.

A longer leaf and no block should change things up somewhat too. Not sure how well that cooperates with the kelderman kit though.

 

Hmm, the limiter strap idea would be cheap and simple to try. Thanks!

Fordzilla, i do actually have 2 rubber isolators on the rear trans mounting arrangement. I left that part out in prior post trying to keep it short. The stack looks like a combination of some stock getrag parts and the square pc of tubing. The nv4500 swap was done using an Advanced Adapers bellhousing so it could have very well been part of the kit from whenever the nv4500 swap was done.

Pic attached is the crossmember, getrag plate, and square tubing hanging off the trans ( on an engine stand...) Note, i found a thread on DTR dating back to 2007 where user "swampthang" went through a similar project fitting an nv4500 trans mount in his 1st gen after the conversion. Requires some fab work...

 

That ridiculously thin square tubing is part of the Getrag to NV-4500 swap kit that Advanced Adapters sells.
I got the same bracket for my crew cab NV-4500 swap I did years ago.

I also had to move the whole transmission crossmember back one hole back and re drill the frame accordingly.

 

I've never dealt with bag systems (wish I had them) but from my limited knowledge, compression is obviously progressively controlled but as the axle drops and frame raises, the bag expands with less and less resistance. Correct? So I agree that some kind of limiting strap and/or a shock absorber that provides resistance to an expanding bag seems like it would help. But I'm not an engineer, nor do I play one on this forum. Just a dumb farm boy's thinking.

 

Hey guys, I'm hoping to get someone to grab some dimensions off their rear STOCK rear suspension so I can compare. I have no reference to what stock height was in the rear and cant tell by the blocks in the spring pack alone because of the kelderman air setup replacing the rear shackle. My truck is a 1993 4x4.

Two dimensions I'm looking for:
1) height of spacer block between spring pack and axle perch
2) position of rearward leaf spring eyelet in comparison to TOP of frame rail

Pics show examples. 1st one is self explanatory. For 2nd dimension I set a 24" level on top of the frame rail and measured to center of eyebolt in spring. Be careful not to set your straight edge on top of any rivets in this area of the frame rail. I had a few in that area due to spare tire carrier i think...

I know my truck is lifted but I'm trying to determine how much.

 

That is the stock 6 inch block typically found in the 4x4 92-'93 trucks. All the 12V powered club cab '92-'93 4x4 trucks I have seen have the 6 inch blocks.
The '89-'90s 4x4 trucks [usually] have the 3 in block from the factory.
'91.0 and 91.5 Cummins trucks are a mix up of parts usually. I know my 91.0 W250 had the 3 inch block.

I don't have any factory ride trucks in the shop to get the other measurement you seek.

 

Ok Oliver, thanks. Obviously I can't rule out that one of the prior owners put different springs in the rear or added leafs or something. The u bolts look like they've been tampered with (excess threads beyond the nuts) which made me guess at the spacer block initially.

Far as i can tell i'm 3rd or 4th owner so I'm constantly following bread crumb trails,... which i'm sure everyone here is familiar with unless they found a gem.

I'll have to see if anyone else has a stock truck to get that rear spring eyelet dimension off the frame rail.

You've obviously seen alot of 1st gens. Does my truck even look lifted to your eyes? How much psi is in front & rear bags can raise or lower the truck but this photo is around where i typically keep it empty, 15psi in rear and about ~22psi in front to get rid of any rake. Its sitting on donut 31's.

 

Wow that is a nice looking ride!

Take a side picture with the wheels straight, if you can.

I see about 1/4 to 3/4 of an inch about on non lifted Cummins 1st gen measured from the front bump stop down the the surface of the top leaf spring.

It does not appear to be lifted much, if it is. I usually find 33X12.5 can fit a stock truck with no lift. I have also seen half worn, 315R75R16 tires on 16X 8 rims fit with very mild rubbing.

 

Thanks. Its a solid survivor with zero body rot, and i mean zero. Originally a northern montana truck, I bought it from a guy in TX. Was planning to work it, but after getting it home I pulled up damp carpet (water was getting in from those infamous hidden cab/firewall cracks below windshield corners) and the floorboards were just too clean to even consider letting it see salt.

I cant get a level pic of the truck until its back on the ground. Its on blocks inside garage with all the stuff i'm doing to it right now. I'll look to see if I have any other pics though...

You have me starting to wonder if I "leveled" the truck when I had new leafs put up front. I'll have to dig up the order sheet but I thought I had an extra 1-2" put into the new springs from Alcan. That would make sense if these trucks had a slight rake in stock form, right?

 

The '92-'93 Club Cab rigs with the 6 inch block most certainly had a good factory rake to them.
I would guess about 3 inches front to to back unloaded.

Quite often I would recommend adjusting the front springs with an 1 or 2 inch lift or swap out the 6 inch rear blocks for the 3 inch block on those year trucks, if the goal is going for a leveled out truck.


Glad to hear you are saving it form the salt and the worst weather as it sure looks clean in those pictures.

 

Perhaps when new on the dealer lot, but 3" is nothing on a long truck.

The 6" block is normally paired with the HD leaf pack (3/4" eye bolts) that is almost flat. The shorter block is paired with the lighter-duty leafs (5/8" eye bolts) that have more curve.

On my '90 RC, I paired the curvy, lighter leafs with the 6" block to get as much lift as possible.

 

WOW, that is a real nice one!.

I'll try to get a measurement of mine. But right now it's hooked to a trailer with a load of hay.

 

Mine is sitting on uneven ground with an empty 16' tagalong attached and a few things in the bed (spare tires, jack, chains, blocks, etc - a couple hundred pounds I'd guess).

The heights from top of spring eye to top of frame is roughly 3&1/4" and 3 &1/8".