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Series 5 speed kits


5.0 average, based on 4 reviews

Product Information

Adapter kit to mate a LR 5 speed to a Series LR transfer case

We often get asked about putting a 5 speed LT77 or R380 into a Series vehicle. This combination gives a stronger gearbox, synchro on all forward gears and overdrive 5th. There are a few ways of doing this depending on the axles fitted and if it"s an 88" or 109".

The series transfer case is part time 4 wheel drive and the front axle is fitted with Universal Joints (UJ"s). The Defender and Disco is fitted with the LT230 which is full time 4 wheel drive and because of this the front axle has CV joints.

If you have coil sprung axles on your Series then they will have CV joints and thus you can just fit the 5 speed with the LT230 and this will be fine.

If you have stock Leaf sprung axles you have 2 options :

1) You can fit the 5 speed to the engine then modify the LT230 to part time 4 wheel drive and fit this in conjunction with free wheeling hubs on the front. The way this kit works is you fit a few parts inside the LT230 centre diff to change the operation of the diff lock so that in the "diff locked" position the centre diff is locked and you have locked drive to the front and rear props but in the "unlocked" position there is no drive to the front, just the rear, so when used the Free Wheeling Hubs the front prop, diff etc is not spinning. We are able to supply these parts, please see here

2) The other option is to fit the LT77 or R 380 and then fit the series transfer case onto the back of it with this kit. This way you retain the stock "Series" transfer case with selectable 2/4WD. You can also fit freewheeling hubs so you are not wasting fuel spinning the prop, diff Etc. This ends up a shorter transmission and allows you to keep the stock front grill even on a 88".

The gearbox length is increased by 102mm (4ins). The preferred method to accommodate this is to move the engine forward as this entails no change to prop shafts or cross members. Please note on some vehicles you will also need to modify cross members as well. This is not sold as a complete kit to put a 5 speed into a Series as there are many other considerations as mentioned, this kit is just the parts to mate the gearbox to the Series transfer case.

Note this kit cannot be used with the series high ratio transfer case kit, PTO or overdrive.


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Product Code: LR77 KIT

Installation Information » (Click to Expand Collapse)

Note- this conversion increases the length of the transmission by 102mm overall i.e. the engine mounts must move forward or the gearbox mounts back by this amount.

LR77 Conversion Fitting notes You should have received,

1 x conversion plate with brg housing,

4 dowels, brg outer and seal

1 x input gear with brgs

1 x PTO cover with brg outer

1 x transfer case inspection plate

1 x selector shaft cover plate

1 x breather pipe and banjo bolt

1 x high / low lever mounting bracket (angle iron 10?)

8 x M10 x 30 cap heads (plate to LT 77)

1 x M10 x 40 cap head (plate to LT 77 dowel)

3 x M10 x 30 hex heads (transfer box to plate)

3 x M10 plain washers (transfer box to plate, inside)

3 x M10 spring washer (transfer box to plate, inside)

1 Pre assemble plate to transfer case, fit new gear and PTO cover plate, use no gasket on PTO. Check the pre load on the input gear if necessary add a gasket to the PTO cover. Mark the transfer case along the top edge of the conversion plate. Check the side to ensure the cap head bolt, used to bolt the plate to the LT 77, will fit. It may be necessary to trim the edge of the transfer case to clear the bolt head.

2 Disassemble and fit the conversion plate to the LT 77 gearbox. For LT77 only cut the top off the transfer case lobe level with the top edge of the conversion plate, to clear the reverse light switch this is not necessary on R380. The rest of the assembly proceeds as normal.

3 Check the plate fits on the LT 77 properly before bolting up.

4 When assembling the transfer case to the LT 77 do not use a gasket, use RTV and also fill the vertical vent slot to prevent oil leaking out, the vent is now via an axle breather in the top cover plate.

5 Because of the increased length of the LT 77 the H/L bracket will need a new support. Weld the angle iron supplied to the RH gearbox bracket as indicated in the sketch.

6 When assembling the transfer case to the LT77 use EP90 oil on the spline, grease should not be used. The gear has been drilled to allow splash lubrication of the spline.

Technical Information / FAQ's » (Click to Expand Collapse)

Please note if you are fitting this kit the diameter indicated below must be the larger 108mm rather than the smaller 88mm version.

Customer Reviews

Average Rating: 5

Does exactly what it should

Easy to understand and to fit. Done 100s of miles with this on a high output 200tdi running lt77 now using with the r380 stumpy from D.A. I like this kit because I like using the old virtually bomb proof series transfer box.

Emmo :: Aug 18 2019, 11:40 AM

Series 5 speed adaptor

Forgot to add 5 stars to previous review so sorry

Philip Evans :: Jan 29 2019, 06:36 AM

Series 5 speed adaptor

Well engineered strong quality materials and parts all giving the impression it should outlast the gearbox , not the clearest instructions but not to difficult once trial fitted to work it all out. Picture on the web site does give impression of inclusive gaskets & bearings already fitted in both cases this is not so but these are minor points . I did find I had the wrong size hole in my suffix D trans box but got a friend to open this up and so now have a much better transmission i can't believe how noisey the old 4 speed was. David & All the staff were very helpful & patient with my dumb questions I really couldn't have asked for better service or parts Ascroft will be my go to transmission place from now on

Philip Evans :: Jan 27 2019, 16:06 PM

Series 5 speed adapter

I have used two of these adapter kits behind a 200 Tdi in a series II and a 2.25 petrol in a IIa. The craftsmanship is great and they perform flawlessly. What a great idea! Shipping to the USA was painless and fast.

Gary Heard :: Sep 21 2017, 16:58 PM

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