R2.8 to Ashcroft HD R380 stumpy Conversions

Uncle Douglas

Well-known member
Chris wants new threads so going to splinter off and document what we are doing.
I'm not in love with using automatics behind diesels. Maybe its just me being old school. I built a v8 manual trail 90 just to force Trey to learn to drive a stick. To me the much greater compression braking you get from a diesel that is only able to be utilized with a manual is a big deal, and then there is economy/range is important.
We have 5 spec built radiators and intercoolers now ready to ship to us after a long wait. After meeting with Steve @ the Cummins booth @ Expo East I got in touch with Chad Mckinney/Quickdraw Brands and got him fired up to develop a custom bell housing for the short R380. I did this based on others he had on display in the Cummins booth. He's having a prototype cut out of a billet block for me and expects to have it in my hands third week of January. We are going this route rather than wait for castings which will likely take until March. A new bellhousing is a better mousetrap than trying to utilize an adapter ring and allows us to use the flywheel Cummins supplies with the engine.
I sent him a stumpy as well as a Rover clutch but asked that he figure out the largest beefiest clutch disc that had the same spline configuration as the Rover trans. He laughed when he saw the stock Rover 4cyl clutch disc I sent him for mock up. Chad found that an early 70's Chrysler V8 clutch disc fits perfectly so we will be using these readily available off the shelf, complete 70's muscle car clutch setup with these Cummins to R380 kits.
Once we've got this dialed in, a diy'er you will be able to purchase an off the shelf kit from Chad @ Quickdraw.
In the future the stumpys we order will be sans bell housing which should help a good bit with the price from Ashcrofts.
 

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WK2Burner

Well-known member
forgive my ignorance, I thought the stumpy aside from some internals was just as shorter bellhousing? only reason i ask is would it be cheaper if you sourced or had a regular 380, and just purchased the remaining conversion parts, likely saving on all that shipping.

*this is just out of educational curiosity. and that setup looks like the bees knees for an off the shelf deal once it's ready.
 

Mack

Active member
With this bellhousing, does the lt230 remain in its stock location? Are all 5 of your inter cooler/radiator setups spoken for?
 

Uncle Douglas

Well-known member
that clutch is huge. i love it. must be a very tight fit with the pressure plate.

adam
Not @ all with the new 5.5 inch deep bellhoousing that flares out to mate to the r2.8 block. Pictured is the ashcroft 4 cyl stumpy belhousing, yeah its puny which is why an adapter ring was still going to limit clutch component size-ie was going to be a problem.
 

Uncle Douglas

Well-known member
With this bellhousing, does the lt230 remain in its stock location? Are all 5 of your inter cooler/radiator setups spoken for?
Designing this to be direct fit with lt77 floors/tunnels/seatbox trucks, those are the most common ones needing repower.
Yes lt230 remains in same place, uses stock tcase frame mounts and prop shafts.

Yes have 6 conversions lined up, so odering 5 more and while we hope for a quicker resupply, dont have an eta.
 

donb

Well-known member
Great stuff Doug!

Agree with the manual gearbox move. I know the modern day autos with up to 10 speeds are all that and then some but there is something special about a turbo diesel and manual transmission.

What pressure plate is used and does is bolt to the R2.8 flywheel? Crazy how small the Rover clutch is on the R2.8.


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Uncle Douglas

Well-known member
forgive my ignorance, I thought the stumpy aside from some internals was just as shorter bellhousing? only reason i ask is would it be cheaper if you sourced or had a regular 380, and just purchased the remaining conversion parts, likely saving on all that shipping.

*this is just out of educational curiosity. and that setup looks like the bees knees for an off the shelf deal once it's ready.
Shipping cost is kind of the last of the considerations here.

There are three versions of an r380. 300 Tdi, Rover v8, and the stumpy designed to replace an lt77.

The engine we are working with makes more torque (seat of the pants power) than any engine rover ever put in a defender. IE a stock transmission will not last for any reasonable period of time. Dave Ashcroft is confident his HD version can withstand 400 ft lbs of torque.

For this reason we are utilizing Ashcrofts HD bearing set/ built to order stumpy's. Ashcroft has the bellhousings for the stumpy cast and they are expensive, so ordering one without that bell housing will be a savings.

No a 300 tdi, or V8 r380 would not be suitable as both of those are much longer setups and push the engine forward in the engine compartment. They also require that we swap out, floors, seatbox flange, and tunnels etc as the transfer case is slightly further forward and fouls on the seatbox. Additionally those transmissions would still require an adapter ring and custom flywheel (more expensive and less than ideal setups) in order to mate to the Cummins. In the case of the long bellhousing 300 tdi r380 the bell housing still has the same issue in that you have to use the toy sized rover clutch mechanism.
 

Uncle Douglas

Well-known member
Great stuff Doug!

Agree with the manual gearbox move. I know the modern day autos with up to 10 speeds are all that and then some but there is something special about a turbo diesel and manual transmission.

What pressure plate is used and does is bolt to the R2.8 flywheel? Crazy how small the Rover clutch is on the R2.8.


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We will use the massive Chrysler V8 pressure plate, and throw out bearing that corresponds to that clutch disc. We will drill and tap the cummins flywheel to accept that bolt pattern.
 

Uncle Douglas

Well-known member
I should have been clear- pictured is an Ashcroft r380 stumpy with their bellhousing
with the two different clutch discs slid on just to show the difference.

We are not using this bell housing. Anyone want to buy 4 Ashcrofts Stumpy bell housings ?
 

Red90

Well-known member
forgive my ignorance, I thought the stumpy aside from some internals was just as shorter bellhousing? only reason i ask is would it be cheaper if you sourced or had a regular 380, and just purchased the remaining conversion parts, likely saving on all that shipping.

*this is just out of educational curiosity. and that setup looks like the bees knees for an off the shelf deal once it's ready.
Ashcroft lists the conversion parts here: https://www.ashcroft-transmissions.co.uk/index.php?act=viewCat&catId=99

Since the input shaft must be changed, it requires a complete teardown.
 

WK2Burner

Well-known member
Ashcroft lists the conversion parts here: https://www.ashcroft-transmissions.co.uk/index.php?act=viewCat&catId=99

Since the input shaft must be changed, it requires a complete teardown.
I'm tracking now. Just thought it easier to buy the conversion parts and use your own R380 sourced here, sans the bellhousing if it's not needed for the 2.8. Doubt in near future ill be moving off my 200 unless required, but was curious to understand more the difference of the stumpy and standard. Easier bet to have them deliver a turnkey stumpy, but was more curious for DIY.
 

Red90

Well-known member
I'm tracking now. Just thought it easier to buy the conversion parts and use your own R380 sourced here, sans the bellhousing if it's not needed for the 2.8. Doubt in near future ill be moving off my 200 unless required, but was curious to understand more the difference of the stumpy and standard. Easier bet to have them deliver a turnkey stumpy, but was more curious for DIY.
The other thing is Doug is using ones with an upgraded rear bearings. Without this, you may be pushing the limits of the box.
 

donb

Well-known member
That's the deal breaker

Deal breaker for using the V8 or 300tdi? It sounds like those gearboxes won?t work behind an R2.8 anyway. If the input shafts are the weak link on the R380 then swapping input shafts might solve 2 issues (length and strength).

The R2.8 is going to need a pretty strong tranny behind it no matter which one you use (AX15, NV3500, R380 or ?). Idk what Ashcroft charges for an HD stumpy R380 w/out a BH but it sounds like Doug?s architecture simplifies an R2.8 install into a 2.5 chassis which will save on install price one way or another.


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Red90

Well-known member
If the input shafts are the weak link on the R380 then swapping input shafts might solve 2 issues (length and strength).
?? The input shafts are not the weak link. Ashcroft installs larger layshaft and mainshaft rear bearings. This has nothing to do with the input/pinion shaft. The input shaft is changed in order to make the box shorter, so that the engine clears the steering box. This make it the same overall length as the short LT77s.
 

Uncle Douglas

Well-known member
Doug's architecture simplifies an R2.8 install into a 2.5 chassis which will save on install price one way or another.


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Not just 2.5's. Everything up to 1994 except V8 powered trucks.


From Ashcrofts site
"Heavy Duty Rear Support Bearings

One of the common failure modes of the R380 is premature wear of one or both of the rear support bearings in the rear 5th speed aluminium housing, this starts as a whirring in all gears but not so bad in 4th, then as the bearings wear it allows the 5th gear on the layshaft and 5th gear on the mainshaft to come a little out of mesh, then 5th also gets noisy and often results in the teeth coming off one or both of the 5th gears, after much design work we are now able to offer to upgrade these two bearings.

The Layshaft rear support bearing is FTC2385, this is made by RHP and has a dynamic load rating of 27Kn, we replace this with a larger bearing of equivalent quality which has a dynamic load rating of 35.5Kn, this is a 31% increase. See below a comparison photo of stock vs our HD one.

The Mainshaft rear support bearing is FTC3371, this is made by RHP and has a dynamic load rating of 27.4Kn, we replace this with a larger bearing of equivalent quality which has a dynamic load rating of 44Kn, this is a 60% increase. See below a comparison photo of stock vs our HD one.

This upgrade would be advised for any hard working R380 such as heavy/tuned TD5 vehicles, ie overlanders or tow vehicles,

The cost of this upgrade is an additional ?160 ontop of the R380 rebuilt unit."
 

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