88-98 Solid Axle Conversion for GMT400 Trucks

Ford Dana 44

We generally ignore the '75 and older axles as they're all drum brake and low pinion.

Coil sprung F150 and Bronco axles do not work either, most will fall into pieces if you cut the radius arm mounts off as they're integral to the housing/tube.

'76-77 F250 Dana 44's work well with our solid axle conversion, they use a 31.5" spring pad width. Low pinion, same driver's side drop differential as the GMT400 transfer case, these will have "flat top" style knuckles that can be machined for crossover steering.

'77.5-79 F250 Dana 44's also work well with our solid axle conversion, they use a high pinion differential, 31.5" spring pad width. High pinion, same driver's side drop differential as the GMT400 transfer case, these will have "flat top" style knuckles that can be machined for crossover steering.

Ford Dana 60

'77.5-79 F250 (sometimes) and F350, high pinion, 31.5" spring pad width, these work great for our solid axle conversion but the narrow year range makes them hard to find. High Pinion, same driver's side drop differential as the GMT400 transfer case, they use kingpin knuckles that can easily accept crossover steering.

'80-84 Ford didn't use solid axles in any of their trucks, they all used the TTB/IFS.

'85-91 F350 Dana 60's are a good candidate, and the wider year range makes them more available. They use a wider 36.5" spring pad width that can let big tires rub on the spring and limit steering angle (say, 37" or bigger roughly, depending on wheel choice as well). High pinion, same driver's side drop differential as the GMT400 transfer case, they use kingpin knuckles that can easily accept crossover steering.

'92-97 F350 axles fit our solid axle conversion as well, they share the same 36.5" spring pad width as the '85-91 axles. However, they use balljoint knuckles that we don't have a crossover steering system for. High pinion, same driver's side drop differential as the GMT400 transfer case.

'99-04 F250 and F350 Dana 60's have even wider spring perches yet at 37-1/2". We've had customers make these axles work but keep in mind that our 36.5" solid axle conversion kit officially sets the springs 36" apart (due to the GM frame width) and the driver's side perch on the Dana 60 is machined into the differential so you can't really move the spring perches. These also use balljoint knuckles that we do not make crossover steering for. High pinion, same driver's side drop differential as the GMT400 transfer case. We don't really have much details other than that to make this axle work.

'05+ Ford Dana 60's are all radius arm/coil sprung and do not work with our solid axle conversion.

GM Dana 44 and corporate 10 bolt

'71-87 GM 1/2 and 3/4 ton pickups, '71-91 Blazers and Suburbans, all with 32" spring pad widths. Very common, but the front differential is on the passenger's side so the transfer case will need to be swapped to match if you want to keep 4WD. '76 and older models will have flat top style knuckles that can be machined for crossover steering, '77 and newer models require a new Reid Racing knuckle

GM Dana 60

'76-91 K30 and V30 Chevy axles are good candidates, all with 32" spring pad widths. They have kingpin knuckles that are already setup for crossover steering, but the front differential is on the passenger's side so the transfer case will need to be swapped to match if you want to keep 4WD.

Dodge Dana 60

'75-93 W250 (sometimes) and W350, all with 32-1/2" spring pad widths. They have kingpin knuckles that are already setup for crossover steering, but the front differential is on the passenger's side so the transfer case will need to be swapped to match if you want to keep 4WD.

'94-02 Dodge Dana 60's come from the factory with link/coil suspension, they do not work with our solid axle conversion. Placement of leaf spring perches aside, there are also no options for crossover steering.

The 1500 and 2500 Chevy's from 1988-1998 use an NP241 (floor shift), NP243 (Push button, 2HI, 4HI, 4LO) or an NP246 (Push button, Autotrac, 2HI, 4HI, 4LO, AUTO4WD). The 3500 trucks had either a Borg Warner 4401 or 4470 transfer case. If your truck has the NP246 Autotrac transfer case, you'll have to swap it as it doesn't work correctly without the front axle sensors. The Autotrac transfer case has push button switches on the dash with an auto-4WD option.

The NP241, NP243, and either Borg Warner transfer case works fine but you'll need to use a Ford front axle because they all put the driveshaft on the driver's side. The Ford 205 isn't a difficult retrofit either, as a higher strength option, call us for details on adapting a Ford 205 (or any of our gear reduction systems) to a GM transmission.

If you're using a GM or Dodge front axle, you'll need to change the transfer case to one that sets the driveshaft on the passenger side. The transmission does need to be the 4WD version so 2WD transmissions will need to be converted. Adding in any of our gear reduction systems is relatively easy, give use a call to discuss those options. Swap info for a single transfer case is as follows, there are three main options:

GM NP208

This is an easy option because it has the same bolt pattern as the 88-98 transmissions and is a fairly durable transfer case using up to 37" tires. If you have a 700R4/4L60E, you'll want to find an NP208 from behind a 700R4 and those came in most 81-87 Chevy 1/2 tons (88 Suburbans and Blazers too!), these will have a 27 spline input. Those will bolt right in, the only issue is the 208's use a cable driven speedometer and the 4L60E needs an electric speed signal to shift correctly. That can be solved by installing an adapter that creates an electric signal from the cable drive, you can also put a manual valve body in the trans.

If you have a 4L80E or any of the manual transmissions, you'll need to find an NP208 from a TH400 or an SM465 four speed manual, those will have a 32 spline input. Again, the NP208 will bolt right up in place of the factory transfer case. The 4L80E will need an electric vehicle speed sensor or a manual valve body, the manuals will only need an electric speed sensor if you want the OE speedometer to work.

GM NP241

Another easy option because it bolts right up in place of the factory transfer case on the 88-98's, same duty level as the 208. NP241's came in 89-91 Blazers and Suburbans and they are passenger drop, the 1989 models have a cable driven speedometer just like the 208. The 90 and 91 models, however, use an electric speed sensor in them from the factory so this makes them a very desirable case for solid axle conversions, though they aren't as common as the 208. The 241 is the same story as the 208, if you have a 700R4/4L60E, look for a 241 from a 700R4.

If you have a 4L80E or any of the manual transmissions, look for a 241 from behind a TH400.

GM NP205

The NP205 is the strongest choice, but doesn't bolt directly to any of the 88-98 transmissions. If you have a 700R4/4L60E transmission, you'll want the 205 and adapter system from behind a TH350 transmission. You'll need a shorter output shaft or a spacer: http://offroaddesign.com/catalog/trannyoutput.htm http://offroaddesign.com/catalog/700r4spacer.htm and if it's the later 6 bolt tailhousing (with a removable bellhousing) you'll need a 6 to 4 bolt reducer.

If you have a 4L80E transmission, you have two options to get a 205 on it. You can use an '84 and older figure 8 pattern NP205, swap a long 32 spline input gear into it and use a TH400/fig 8 205 adapter that needs minor machine work to fit the 4L80E. You can also find an '85-91 GM 205 that will have a six bolt round pattern on the front, the input gear needs to be swapped to the short 32 spline version (direct swap) and the factory adapter needs to be notched, then it bolts up. If you have any of the manual transmissions, you'd need to find an '85-91 GM round pattern 205, swap it to the short 32 spline input gear (direct swap) and notch the tail housing of the trans, then it bolts up.

The brackets are exactly the same, the difference is simply in the spring eye bushings we supply with the kit. OE springs and aftermarket springs take different bushings.

The 88-98 Chevy 4WD 1500, 2500 and 3500 frames and the 2WD 1500 frames are all very similar and our solid axle conversion works on those trucks without issue.
The 88-98 2WD 2500 and 3500 trucks are different. Their frames drop down lower then curve up at the front and do not have a flat part to attach the spring hangers to. It is possible to put a solid axle under these trucks but the frame will have to be modified to mimic a 4WD truck or you'll have to graft 4WD front frame rails on to the 2WD frame.